Which is a better name and also better to collect other things. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
2105 lines
72 KiB
C
2105 lines
72 KiB
C
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#include <config.h>
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#include <malloc.h>
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#include <string.h>
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#include <memory.h>
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#include <stdio.h>
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#include <module.h>
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/*
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A version of malloc/free/realloc written by Doug Lea and released to the
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public domain. Send questions/comments/complaints/performance data
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to dl@cs.oswego.edu
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* VERSION 2.6.6 Sun Mar 5 19:10:03 2000 Doug Lea (dl at gee)
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Note: There may be an updated version of this malloc obtainable at
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ftp://g.oswego.edu/pub/misc/malloc.c
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Check before installing!
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* Why use this malloc?
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This is not the fastest, most space-conserving, most portable, or
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most tunable malloc ever written. However it is among the fastest
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while also being among the most space-conserving, portable and tunable.
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Consistent balance across these factors results in a good general-purpose
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allocator. For a high-level description, see
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http://g.oswego.edu/dl/html/malloc.html
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* Synopsis of public routines
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(Much fuller descriptions are contained in the program documentation below.)
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malloc(size_t n);
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Return a pointer to a newly allocated chunk of at least n bytes, or null
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if no space is available.
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free(Void_t* p);
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Release the chunk of memory pointed to by p, or no effect if p is null.
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realloc(Void_t* p, size_t n);
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Return a pointer to a chunk of size n that contains the same data
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as does chunk p up to the minimum of (n, p's size) bytes, or null
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if no space is available. The returned pointer may or may not be
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the same as p. If p is null, equivalent to malloc. Unless the
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#define REALLOC_ZERO_BYTES_FREES below is set, realloc with a
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size argument of zero (re)allocates a minimum-sized chunk.
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memalign(size_t alignment, size_t n);
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Return a pointer to a newly allocated chunk of n bytes, aligned
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in accord with the alignment argument, which must be a power of
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two.
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valloc(size_t n);
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Equivalent to memalign(pagesize, n), where pagesize is the page
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size of the system (or as near to this as can be figured out from
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all the includes/defines below.)
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pvalloc(size_t n);
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Equivalent to valloc(minimum-page-that-holds(n)), that is,
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round up n to nearest pagesize.
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calloc(size_t unit, size_t quantity);
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Returns a pointer to quantity * unit bytes, with all locations
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set to zero.
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cfree(Void_t* p);
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Equivalent to free(p).
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malloc_trim(size_t pad);
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Release all but pad bytes of freed top-most memory back
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to the system. Return 1 if successful, else 0.
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malloc_usable_size(Void_t* p);
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Report the number usable allocated bytes associated with allocated
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chunk p. This may or may not report more bytes than were requested,
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due to alignment and minimum size constraints.
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malloc_stats();
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Prints brief summary statistics on stderr.
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mallinfo()
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Returns (by copy) a struct containing various summary statistics.
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mallopt(int parameter_number, int parameter_value)
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Changes one of the tunable parameters described below. Returns
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1 if successful in changing the parameter, else 0.
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* Vital statistics:
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Alignment: 8-byte
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8 byte alignment is currently hardwired into the design. This
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seems to suffice for all current machines and C compilers.
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Assumed pointer representation: 4 or 8 bytes
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Code for 8-byte pointers is untested by me but has worked
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reliably by Wolfram Gloger, who contributed most of the
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changes supporting this.
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Assumed size_t representation: 4 or 8 bytes
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Note that size_t is allowed to be 4 bytes even if pointers are 8.
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Minimum overhead per allocated chunk: 4 or 8 bytes
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Each malloced chunk has a hidden overhead of 4 bytes holding size
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and status information.
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Minimum allocated size: 4-byte ptrs: 16 bytes (including 4 overhead)
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8-byte ptrs: 24/32 bytes (including, 4/8 overhead)
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When a chunk is freed, 12 (for 4byte ptrs) or 20 (for 8 byte
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ptrs but 4 byte size) or 24 (for 8/8) additional bytes are
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needed; 4 (8) for a trailing size field
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and 8 (16) bytes for free list pointers. Thus, the minimum
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allocatable size is 16/24/32 bytes.
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Even a request for zero bytes (i.e., malloc(0)) returns a
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pointer to something of the minimum allocatable size.
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Maximum allocated size: 4-byte size_t: 2^31 - 8 bytes
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8-byte size_t: 2^63 - 16 bytes
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It is assumed that (possibly signed) size_t bit values suffice to
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represent chunk sizes. `Possibly signed' is due to the fact
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that `size_t' may be defined on a system as either a signed or
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an unsigned type. To be conservative, values that would appear
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as negative numbers are avoided.
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Requests for sizes with a negative sign bit when the request
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size is treaded as a long will return null.
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Maximum overhead wastage per allocated chunk: normally 15 bytes
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Alignnment demands, plus the minimum allocatable size restriction
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make the normal worst-case wastage 15 bytes (i.e., up to 15
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more bytes will be allocated than were requested in malloc), with
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two exceptions:
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1. Because requests for zero bytes allocate non-zero space,
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the worst case wastage for a request of zero bytes is 24 bytes.
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2. For requests >= mmap_threshold that are serviced via
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mmap(), the worst case wastage is 8 bytes plus the remainder
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from a system page (the minimal mmap unit); typically 4096 bytes.
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* Limitations
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Here are some features that are NOT currently supported
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* No user-definable hooks for callbacks and the like.
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* No automated mechanism for fully checking that all accesses
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to malloced memory stay within their bounds.
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* No support for compaction.
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* Synopsis of compile-time options:
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People have reported using previous versions of this malloc on all
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versions of Unix, sometimes by tweaking some of the defines
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below. It has been tested most extensively on Solaris and
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Linux. It is also reported to work on WIN32 platforms.
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People have also reported adapting this malloc for use in
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stand-alone embedded systems.
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The implementation is in straight, hand-tuned ANSI C. Among other
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consequences, it uses a lot of macros. Because of this, to be at
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all usable, this code should be compiled using an optimizing compiler
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(for example gcc -O2) that can simplify expressions and control
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paths.
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__STD_C (default: derived from C compiler defines)
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Nonzero if using ANSI-standard C compiler, a C++ compiler, or
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a C compiler sufficiently close to ANSI to get away with it.
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DEBUG (default: NOT defined)
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Define to enable debugging. Adds fairly extensive assertion-based
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checking to help track down memory errors, but noticeably slows down
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execution.
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REALLOC_ZERO_BYTES_FREES (default: NOT defined)
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Define this if you think that realloc(p, 0) should be equivalent
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to free(p). Otherwise, since malloc returns a unique pointer for
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malloc(0), so does realloc(p, 0).
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HAVE_MEMCPY (default: defined)
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Define if you are not otherwise using ANSI STD C, but still
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have memcpy and memset in your C library and want to use them.
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Otherwise, simple internal versions are supplied.
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USE_MEMCPY (default: 1 if HAVE_MEMCPY is defined, 0 otherwise)
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Define as 1 if you want the C library versions of memset and
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memcpy called in realloc and calloc (otherwise macro versions are used).
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At least on some platforms, the simple macro versions usually
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outperform libc versions.
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HAVE_MMAP (default: defined as 1)
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Define to non-zero to optionally make malloc() use mmap() to
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allocate very large blocks.
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HAVE_MREMAP (default: defined as 0 unless Linux libc set)
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Define to non-zero to optionally make realloc() use mremap() to
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reallocate very large blocks.
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malloc_getpagesize (default: derived from system #includes)
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Either a constant or routine call returning the system page size.
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HAVE_USR_INCLUDE_MALLOC_H (default: NOT defined)
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Optionally define if you are on a system with a /usr/include/malloc.h
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that declares struct mallinfo. It is not at all necessary to
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define this even if you do, but will ensure consistency.
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INTERNAL_SIZE_T (default: size_t)
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Define to a 32-bit type (probably `unsigned int') if you are on a
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64-bit machine, yet do not want or need to allow malloc requests of
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greater than 2^31 to be handled. This saves space, especially for
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very small chunks.
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INTERNAL_LINUX_C_LIB (default: NOT defined)
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Defined only when compiled as part of Linux libc.
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Also note that there is some odd internal name-mangling via defines
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(for example, internally, `malloc' is named `mALLOc') needed
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when compiling in this case. These look funny but don't otherwise
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affect anything.
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WIN32 (default: undefined)
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Define this on MS win (95, nt) platforms to compile in sbrk emulation.
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LACKS_UNISTD_H (default: undefined if not WIN32)
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Define this if your system does not have a <unistd.h>.
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LACKS_SYS_PARAM_H (default: undefined if not WIN32)
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Define this if your system does not have a <sys/param.h>.
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MORECORE (default: sbrk)
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The name of the routine to call to obtain more memory from the system.
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NULL (default: -1)
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The value returned upon failure of MORECORE.
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MORECORE_CLEARS (default 1)
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True (1) if the routine mapped to MORECORE zeroes out memory (which
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holds for sbrk).
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DEFAULT_TRIM_THRESHOLD
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DEFAULT_TOP_PAD
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DEFAULT_MMAP_THRESHOLD
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DEFAULT_MMAP_MAX
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Default values of tunable parameters (described in detail below)
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controlling interaction with host system routines (sbrk, mmap, etc).
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These values may also be changed dynamically via mallopt(). The
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preset defaults are those that give best performance for typical
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programs/systems.
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USE_DL_PREFIX (default: undefined)
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Prefix all public routines with the string 'dl'. Useful to
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quickly avoid procedure declaration conflicts and linker symbol
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conflicts with existing memory allocation routines.
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*/
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#ifndef DEFAULT_TRIM_THRESHOLD
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#define DEFAULT_TRIM_THRESHOLD (128 * 1024)
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#endif
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/*
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M_TRIM_THRESHOLD is the maximum amount of unused top-most memory
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to keep before releasing via malloc_trim in free().
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Automatic trimming is mainly useful in long-lived programs.
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Because trimming via sbrk can be slow on some systems, and can
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sometimes be wasteful (in cases where programs immediately
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afterward allocate more large chunks) the value should be high
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enough so that your overall system performance would improve by
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releasing.
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The trim threshold and the mmap control parameters (see below)
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can be traded off with one another. Trimming and mmapping are
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two different ways of releasing unused memory back to the
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system. Between these two, it is often possible to keep
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system-level demands of a long-lived program down to a bare
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minimum. For example, in one test suite of sessions measuring
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the XF86 X server on Linux, using a trim threshold of 128K and a
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mmap threshold of 192K led to near-minimal long term resource
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consumption.
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If you are using this malloc in a long-lived program, it should
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pay to experiment with these values. As a rough guide, you
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might set to a value close to the average size of a process
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(program) running on your system. Releasing this much memory
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would allow such a process to run in memory. Generally, it's
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worth it to tune for trimming rather tham memory mapping when a
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program undergoes phases where several large chunks are
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allocated and released in ways that can reuse each other's
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storage, perhaps mixed with phases where there are no such
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chunks at all. And in well-behaved long-lived programs,
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controlling release of large blocks via trimming versus mapping
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is usually faster.
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However, in most programs, these parameters serve mainly as
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protection against the system-level effects of carrying around
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massive amounts of unneeded memory. Since frequent calls to
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sbrk, mmap, and munmap otherwise degrade performance, the default
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parameters are set to relatively high values that serve only as
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safeguards.
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The default trim value is high enough to cause trimming only in
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fairly extreme (by current memory consumption standards) cases.
|
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It must be greater than page size to have any useful effect. To
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disable trimming completely, you can set to (unsigned long)(-1);
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||
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*/
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#ifndef DEFAULT_TOP_PAD
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#define DEFAULT_TOP_PAD (0)
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#endif
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/*
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M_TOP_PAD is the amount of extra `padding' space to allocate or
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retain whenever sbrk is called. It is used in two ways internally:
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* When sbrk is called to extend the top of the arena to satisfy
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a new malloc request, this much padding is added to the sbrk
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request.
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* When malloc_trim is called automatically from free(),
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it is used as the `pad' argument.
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In both cases, the actual amount of padding is rounded
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so that the end of the arena is always a system page boundary.
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The main reason for using padding is to avoid calling sbrk so
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often. Having even a small pad greatly reduces the likelihood
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that nearly every malloc request during program start-up (or
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after trimming) will invoke sbrk, which needlessly wastes
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time.
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|
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Automatic rounding-up to page-size units is normally sufficient
|
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to avoid measurable overhead, so the default is 0. However, in
|
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systems where sbrk is relatively slow, it can pay to increase
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this value, at the expense of carrying around more memory than
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the program needs.
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*/
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|
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#ifndef DEFAULT_MMAP_THRESHOLD
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#define DEFAULT_MMAP_THRESHOLD (128 * 1024)
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#endif
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|
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/*
|
||
|
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M_MMAP_THRESHOLD is the request size threshold for using mmap()
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to service a request. Requests of at least this size that cannot
|
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be allocated using already-existing space will be serviced via mmap.
|
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(If enough normal freed space already exists it is used instead.)
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|
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Using mmap segregates relatively large chunks of memory so that
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they can be individually obtained and released from the host
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system. A request serviced through mmap is never reused by any
|
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other request (at least not directly; the system may just so
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happen to remap successive requests to the same locations).
|
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Segregating space in this way has the benefit that mmapped space
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can ALWAYS be individually released back to the system, which
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helps keep the system level memory demands of a long-lived
|
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program low. Mapped memory can never become `locked' between
|
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other chunks, as can happen with normally allocated chunks, which
|
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menas that even trimming via malloc_trim would not release them.
|
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|
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However, it has the disadvantages that:
|
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|
||
1. The space cannot be reclaimed, consolidated, and then
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used to service later requests, as happens with normal chunks.
|
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2. It can lead to more wastage because of mmap page alignment
|
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requirements
|
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3. It causes malloc performance to be more dependent on host
|
||
system memory management support routines which may vary in
|
||
implementation quality and may impose arbitrary
|
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limitations. Generally, servicing a request via normal
|
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malloc steps is faster than going through a system's mmap.
|
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All together, these considerations should lead you to use mmap
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only for relatively large requests.
|
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|
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*/
|
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|
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#ifndef DEFAULT_MMAP_MAX
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#define DEFAULT_MMAP_MAX (0)
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#endif
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|
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/*
|
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M_MMAP_MAX is the maximum number of requests to simultaneously
|
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service using mmap. This parameter exists because:
|
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|
||
1. Some systems have a limited number of internal tables for
|
||
use by mmap.
|
||
2. In most systems, overreliance on mmap can degrade overall
|
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performance.
|
||
3. If a program allocates many large regions, it is probably
|
||
better off using normal sbrk-based allocation routines that
|
||
can reclaim and reallocate normal heap memory. Using a
|
||
small value allows transition into this mode after the
|
||
first few allocations.
|
||
|
||
Setting to 0 disables all use of mmap. If HAVE_MMAP is not set,
|
||
the default value is 0, and attempts to set it to non-zero values
|
||
in mallopt will fail.
|
||
*/
|
||
|
||
/*
|
||
INTERNAL_SIZE_T is the word-size used for internal bookkeeping
|
||
of chunk sizes. On a 64-bit machine, you can reduce malloc
|
||
overhead by defining INTERNAL_SIZE_T to be a 32 bit `unsigned int'
|
||
at the expense of not being able to handle requests greater than
|
||
2^31. This limitation is hardly ever a concern; you are encouraged
|
||
to set this. However, the default version is the same as size_t.
|
||
*/
|
||
|
||
#ifndef INTERNAL_SIZE_T
|
||
#define INTERNAL_SIZE_T size_t
|
||
#endif
|
||
|
||
/*
|
||
REALLOC_ZERO_BYTES_FREES should be set if a call to
|
||
realloc with zero bytes should be the same as a call to free.
|
||
Some people think it should. Otherwise, since this malloc
|
||
returns a unique pointer for malloc(0), so does realloc(p, 0).
|
||
*/
|
||
|
||
/* #define REALLOC_ZERO_BYTES_FREES */
|
||
|
||
/*
|
||
Define HAVE_MMAP to optionally make malloc() use mmap() to
|
||
allocate very large blocks. These will be returned to the
|
||
operating system immediately after a free().
|
||
*/
|
||
|
||
#define HAVE_MMAP 0 /* Not available for barebox */
|
||
|
||
/*
|
||
Define HAVE_MREMAP to make realloc() use mremap() to re-allocate
|
||
large blocks. This is currently only possible on Linux with
|
||
kernel versions newer than 1.3.77.
|
||
*/
|
||
|
||
#undef HAVE_MREMAP /* Not available for barebox */
|
||
|
||
/*
|
||
|
||
This version of malloc supports the standard SVID/XPG mallinfo
|
||
routine that returns a struct containing the same kind of
|
||
information you can get from malloc_stats. It should work on
|
||
any SVID/XPG compliant system that has a /usr/include/malloc.h
|
||
defining struct mallinfo. (If you'd like to install such a thing
|
||
yourself, cut out the preliminary declarations as described above
|
||
and below and save them in a malloc.h file. But there's no
|
||
compelling reason to bother to do this.)
|
||
|
||
The main declaration needed is the mallinfo struct that is returned
|
||
(by-copy) by mallinfo(). The SVID/XPG malloinfo struct contains a
|
||
bunch of fields, most of which are not even meaningful in this
|
||
version of malloc. Some of these fields are are instead filled by
|
||
mallinfo() with other numbers that might possibly be of interest.
|
||
|
||
HAVE_USR_INCLUDE_MALLOC_H should be set if you have a
|
||
/usr/include/malloc.h file that includes a declaration of struct
|
||
mallinfo. If so, it is included; else an SVID2/XPG2 compliant
|
||
version is declared below. These must be precisely the same for
|
||
mallinfo() to work.
|
||
|
||
*/
|
||
|
||
/* #define HAVE_USR_INCLUDE_MALLOC_H */
|
||
|
||
|
||
/* SVID2/XPG mallinfo structure */
|
||
|
||
struct mallinfo
|
||
{
|
||
int arena; /* total space allocated from system */
|
||
int ordblks; /* number of non-inuse chunks */
|
||
int smblks; /* unused -- always zero */
|
||
int hblks; /* number of mmapped regions */
|
||
int hblkhd; /* total space in mmapped regions */
|
||
int usmblks; /* unused -- always zero */
|
||
int fsmblks; /* unused -- always zero */
|
||
int uordblks; /* total allocated space */
|
||
int fordblks; /* total non-inuse space */
|
||
int keepcost; /* top-most, releasable (via malloc_trim) space */
|
||
};
|
||
|
||
/* SVID2/XPG mallopt options */
|
||
|
||
#define M_MXFAST 1 /* UNUSED in this malloc */
|
||
#define M_NLBLKS 2 /* UNUSED in this malloc */
|
||
#define M_GRAIN 3 /* UNUSED in this malloc */
|
||
#define M_KEEP 4 /* UNUSED in this malloc */
|
||
|
||
/* mallopt options that actually do something */
|
||
|
||
#define M_TRIM_THRESHOLD -1
|
||
#define M_TOP_PAD -2
|
||
#define M_MMAP_THRESHOLD -3
|
||
#define M_MMAP_MAX -4
|
||
|
||
/*
|
||
Access to system page size. To the extent possible, this malloc
|
||
manages memory from the system in page-size units.
|
||
|
||
The following mechanics for getpagesize were adapted from
|
||
bsd/gnu getpagesize.h
|
||
*/
|
||
|
||
#define malloc_getpagesize 4096
|
||
|
||
/*
|
||
Type declarations
|
||
*/
|
||
|
||
struct malloc_chunk
|
||
{
|
||
INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */
|
||
INTERNAL_SIZE_T size; /* Size in bytes, including overhead. */
|
||
struct malloc_chunk *fd; /* double links -- used only if free. */
|
||
struct malloc_chunk *bk;
|
||
};
|
||
|
||
typedef struct malloc_chunk *mchunkptr;
|
||
|
||
/*
|
||
|
||
malloc_chunk details:
|
||
|
||
(The following includes lightly edited explanations by Colin Plumb.)
|
||
|
||
Chunks of memory are maintained using a `boundary tag' method as
|
||
described in e.g., Knuth or Standish. (See the paper by Paul
|
||
Wilson ftp://ftp.cs.utexas.edu/pub/garbage/allocsrv.ps for a
|
||
survey of such techniques.) Sizes of free chunks are stored both
|
||
in the front of each chunk and at the end. This makes
|
||
consolidating fragmented chunks into bigger chunks very fast. The
|
||
size fields also hold bits representing whether chunks are free or
|
||
in use.
|
||
|
||
An allocated chunk looks like this:
|
||
|
||
|
||
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Size of previous chunk, if allocated | |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Size of chunk, in bytes |P|
|
||
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| User data starts here... .
|
||
. .
|
||
. (malloc_usable_space() bytes) .
|
||
. |
|
||
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Size of chunk |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
|
||
Where "chunk" is the front of the chunk for the purpose of most of
|
||
the malloc code, but "mem" is the pointer that is returned to the
|
||
user. "Nextchunk" is the beginning of the next contiguous chunk.
|
||
|
||
Chunks always begin on even word boundries, so the mem portion
|
||
(which is returned to the user) is also on an even word boundary, and
|
||
thus double-word aligned.
|
||
|
||
Free chunks are stored in circular doubly-linked lists, and look like this:
|
||
|
||
chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Size of previous chunk |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
`head:' | Size of chunk, in bytes |P|
|
||
mem-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Forward pointer to next chunk in list |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Back pointer to previous chunk in list |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
| Unused space (may be 0 bytes long) .
|
||
. .
|
||
. |
|
||
nextchunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
`foot:' | Size of chunk, in bytes |
|
||
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
||
|
||
The P (PREV_INUSE) bit, stored in the unused low-order bit of the
|
||
chunk size (which is always a multiple of two words), is an in-use
|
||
bit for the *previous* chunk. If that bit is *clear*, then the
|
||
word before the current chunk size contains the previous chunk
|
||
size, and can be used to find the front of the previous chunk.
|
||
(The very first chunk allocated always has this bit set,
|
||
preventing access to non-existent (or non-owned) memory.)
|
||
|
||
Note that the `foot' of the current chunk is actually represented
|
||
as the prev_size of the NEXT chunk. (This makes it easier to
|
||
deal with alignments etc).
|
||
|
||
The two exceptions to all this are
|
||
|
||
1. The special chunk `top', which doesn't bother using the
|
||
trailing size field since there is no
|
||
next contiguous chunk that would have to index off it. (After
|
||
initialization, `top' is forced to always exist. If it would
|
||
become less than MINSIZE bytes long, it is replenished via
|
||
malloc_extend_top.)
|
||
|
||
2. Chunks allocated via mmap, which have the second-lowest-order
|
||
bit (IS_MMAPPED) set in their size fields. Because they are
|
||
never merged or traversed from any other chunk, they have no
|
||
foot size or inuse information.
|
||
|
||
Available chunks are kept in any of several places (all declared below):
|
||
|
||
* `av': An array of chunks serving as bin headers for consolidated
|
||
chunks. Each bin is doubly linked. The bins are approximately
|
||
proportionally (log) spaced. There are a lot of these bins
|
||
(128). This may look excessive, but works very well in
|
||
practice. All procedures maintain the invariant that no
|
||
consolidated chunk physically borders another one. Chunks in
|
||
bins are kept in size order, with ties going to the
|
||
approximately least recently used chunk.
|
||
|
||
The chunks in each bin are maintained in decreasing sorted order by
|
||
size. This is irrelevant for the small bins, which all contain
|
||
the same-sized chunks, but facilitates best-fit allocation for
|
||
larger chunks. (These lists are just sequential. Keeping them in
|
||
order almost never requires enough traversal to warrant using
|
||
fancier ordered data structures.) Chunks of the same size are
|
||
linked with the most recently freed at the front, and allocations
|
||
are taken from the back. This results in LRU or FIFO allocation
|
||
order, which tends to give each chunk an equal opportunity to be
|
||
consolidated with adjacent freed chunks, resulting in larger free
|
||
chunks and less fragmentation.
|
||
|
||
* `top': The top-most available chunk (i.e., the one bordering the
|
||
end of available memory) is treated specially. It is never
|
||
included in any bin, is used only if no other chunk is
|
||
available, and is released back to the system if it is very
|
||
large (see M_TRIM_THRESHOLD).
|
||
|
||
* `last_remainder': A bin holding only the remainder of the
|
||
most recently split (non-top) chunk. This bin is checked
|
||
before other non-fitting chunks, so as to provide better
|
||
locality for runs of sequentially allocated chunks.
|
||
|
||
* Implicitly, through the host system's memory mapping tables.
|
||
If supported, requests greater than a threshold are usually
|
||
serviced via calls to mmap, and then later released via munmap.
|
||
|
||
*/
|
||
|
||
/* sizes, alignments */
|
||
|
||
#define SIZE_SZ (sizeof(INTERNAL_SIZE_T))
|
||
#define MALLOC_ALIGNMENT (SIZE_SZ + SIZE_SZ)
|
||
#define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
|
||
#define MINSIZE (sizeof(struct malloc_chunk))
|
||
|
||
/* conversion from malloc headers to user pointers, and back */
|
||
|
||
#define chunk2mem(p) ((void*)((char*)(p) + 2*SIZE_SZ))
|
||
#define mem2chunk(mem) ((mchunkptr)((char*)(mem) - 2*SIZE_SZ))
|
||
|
||
/* pad request bytes into a usable size */
|
||
|
||
#define request2size(req) \
|
||
(((long)((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) < \
|
||
(long)(MINSIZE + MALLOC_ALIGN_MASK)) ? MINSIZE : \
|
||
(((req) + (SIZE_SZ + MALLOC_ALIGN_MASK)) & ~(MALLOC_ALIGN_MASK)))
|
||
|
||
/* Check if m has acceptable alignment */
|
||
|
||
#define aligned_OK(m) (((unsigned long)((m)) & (MALLOC_ALIGN_MASK)) == 0)
|
||
|
||
/*
|
||
Physical chunk operations
|
||
*/
|
||
|
||
/* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
|
||
|
||
#define PREV_INUSE 0x1
|
||
|
||
/* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
|
||
|
||
#define IS_MMAPPED 0x2
|
||
|
||
/* Bits to mask off when extracting size */
|
||
|
||
#define SIZE_BITS (PREV_INUSE|IS_MMAPPED)
|
||
|
||
/* Ptr to next physical malloc_chunk. */
|
||
|
||
#define next_chunk(p) ((mchunkptr)( ((char*)(p)) + ((p)->size & ~PREV_INUSE) ))
|
||
|
||
/* Ptr to previous physical malloc_chunk */
|
||
|
||
#define prev_chunk(p)\
|
||
((mchunkptr)( ((char*)(p)) - ((p)->prev_size) ))
|
||
|
||
/* Treat space at ptr + offset as a chunk */
|
||
|
||
#define chunk_at_offset(p, s) ((mchunkptr)(((char*)(p)) + (s)))
|
||
|
||
/*
|
||
Dealing with use bits
|
||
*/
|
||
|
||
/* extract p's inuse bit */
|
||
|
||
#define inuse(p)\
|
||
((((mchunkptr)(((char*)(p))+((p)->size & ~PREV_INUSE)))->size) & PREV_INUSE)
|
||
|
||
/* extract inuse bit of previous chunk */
|
||
|
||
#define prev_inuse(p) ((p)->size & PREV_INUSE)
|
||
|
||
/* check for mmap()'ed chunk */
|
||
|
||
#define chunk_is_mmapped(p) ((p)->size & IS_MMAPPED)
|
||
|
||
/* set/clear chunk as in use without otherwise disturbing */
|
||
|
||
#define set_inuse(p)\
|
||
((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size |= PREV_INUSE
|
||
|
||
#define clear_inuse(p)\
|
||
((mchunkptr)(((char*)(p)) + ((p)->size & ~PREV_INUSE)))->size &= ~(PREV_INUSE)
|
||
|
||
/* check/set/clear inuse bits in known places */
|
||
|
||
#define inuse_bit_at_offset(p, s)\
|
||
(((mchunkptr)(((char*)(p)) + (s)))->size & PREV_INUSE)
|
||
|
||
#define set_inuse_bit_at_offset(p, s)\
|
||
(((mchunkptr)(((char*)(p)) + (s)))->size |= PREV_INUSE)
|
||
|
||
#define clear_inuse_bit_at_offset(p, s)\
|
||
(((mchunkptr)(((char*)(p)) + (s)))->size &= ~(PREV_INUSE))
|
||
|
||
/*
|
||
Dealing with size fields
|
||
*/
|
||
|
||
/* Get size, ignoring use bits */
|
||
|
||
#define chunksize(p) ((p)->size & ~(SIZE_BITS))
|
||
|
||
/* Set size at head, without disturbing its use bit */
|
||
|
||
#define set_head_size(p, s) ((p)->size = (((p)->size & PREV_INUSE) | (s)))
|
||
|
||
/* Set size/use ignoring previous bits in header */
|
||
|
||
#define set_head(p, s) ((p)->size = (s))
|
||
|
||
/* Set size at footer (only when chunk is not in use) */
|
||
|
||
#define set_foot(p, s) (((mchunkptr)((char*)(p) + (s)))->prev_size = (s))
|
||
|
||
/*
|
||
Bins
|
||
|
||
The bins, `av_' are an array of pairs of pointers serving as the
|
||
heads of (initially empty) doubly-linked lists of chunks, laid out
|
||
in a way so that each pair can be treated as if it were in a
|
||
malloc_chunk. (This way, the fd/bk offsets for linking bin heads
|
||
and chunks are the same).
|
||
|
||
Bins for sizes < 512 bytes contain chunks of all the same size, spaced
|
||
8 bytes apart. Larger bins are approximately logarithmically
|
||
spaced. (See the table below.) The `av_' array is never mentioned
|
||
directly in the code, but instead via bin access macros.
|
||
|
||
Bin layout:
|
||
|
||
64 bins of size 8
|
||
32 bins of size 64
|
||
16 bins of size 512
|
||
8 bins of size 4096
|
||
4 bins of size 32768
|
||
2 bins of size 262144
|
||
1 bin of size what's left
|
||
|
||
There is actually a little bit of slop in the numbers in bin_index
|
||
for the sake of speed. This makes no difference elsewhere.
|
||
|
||
The special chunks `top' and `last_remainder' get their own bins,
|
||
(this is implemented via yet more trickery with the av_ array),
|
||
although `top' is never properly linked to its bin since it is
|
||
always handled specially.
|
||
|
||
*/
|
||
|
||
#define NAV 128 /* number of bins */
|
||
|
||
typedef struct malloc_chunk *mbinptr;
|
||
|
||
/* access macros */
|
||
|
||
#define bin_at(i) ((mbinptr)((char*)&(av_[2*(i) + 2]) - 2*SIZE_SZ))
|
||
#define next_bin(b) ((mbinptr)((char*)(b) + 2 * sizeof(mbinptr)))
|
||
#define prev_bin(b) ((mbinptr)((char*)(b) - 2 * sizeof(mbinptr)))
|
||
|
||
/*
|
||
The first 2 bins are never indexed. The corresponding av_ cells are instead
|
||
used for bookkeeping. This is not to save space, but to simplify
|
||
indexing, maintain locality, and avoid some initialization tests.
|
||
*/
|
||
|
||
#define top (bin_at(0)->fd) /* The topmost chunk */
|
||
#define last_remainder (bin_at(1)) /* remainder from last split */
|
||
|
||
/*
|
||
Because top initially points to its own bin with initial
|
||
zero size, thus forcing extension on the first malloc request,
|
||
we avoid having any special code in malloc to check whether
|
||
it even exists yet. But we still need to in malloc_extend_top.
|
||
*/
|
||
|
||
#define initial_top ((mchunkptr)(bin_at(0)))
|
||
|
||
/* Helper macro to initialize bins */
|
||
|
||
#define IAV(i) bin_at(i), bin_at(i)
|
||
|
||
static mbinptr av_[NAV * 2 + 2] = {
|
||
NULL, NULL,
|
||
IAV (0), IAV (1), IAV (2), IAV (3), IAV (4), IAV (5), IAV (6), IAV (7),
|
||
IAV (8), IAV (9), IAV (10), IAV (11), IAV (12), IAV (13), IAV (14),
|
||
IAV (15),
|
||
IAV (16), IAV (17), IAV (18), IAV (19), IAV (20), IAV (21), IAV (22),
|
||
IAV (23),
|
||
IAV (24), IAV (25), IAV (26), IAV (27), IAV (28), IAV (29), IAV (30),
|
||
IAV (31),
|
||
IAV (32), IAV (33), IAV (34), IAV (35), IAV (36), IAV (37), IAV (38),
|
||
IAV (39),
|
||
IAV (40), IAV (41), IAV (42), IAV (43), IAV (44), IAV (45), IAV (46),
|
||
IAV (47),
|
||
IAV (48), IAV (49), IAV (50), IAV (51), IAV (52), IAV (53), IAV (54),
|
||
IAV (55),
|
||
IAV (56), IAV (57), IAV (58), IAV (59), IAV (60), IAV (61), IAV (62),
|
||
IAV (63),
|
||
IAV (64), IAV (65), IAV (66), IAV (67), IAV (68), IAV (69), IAV (70),
|
||
IAV (71),
|
||
IAV (72), IAV (73), IAV (74), IAV (75), IAV (76), IAV (77), IAV (78),
|
||
IAV (79),
|
||
IAV (80), IAV (81), IAV (82), IAV (83), IAV (84), IAV (85), IAV (86),
|
||
IAV (87),
|
||
IAV (88), IAV (89), IAV (90), IAV (91), IAV (92), IAV (93), IAV (94),
|
||
IAV (95),
|
||
IAV (96), IAV (97), IAV (98), IAV (99), IAV (100), IAV (101), IAV (102),
|
||
IAV (103),
|
||
IAV (104), IAV (105), IAV (106), IAV (107), IAV (108), IAV (109),
|
||
IAV (110), IAV (111),
|
||
IAV (112), IAV (113), IAV (114), IAV (115), IAV (116), IAV (117),
|
||
IAV (118), IAV (119),
|
||
IAV (120), IAV (121), IAV (122), IAV (123), IAV (124), IAV (125),
|
||
IAV (126), IAV (127)
|
||
};
|
||
|
||
/* field-extraction macros */
|
||
|
||
#define first(b) ((b)->fd)
|
||
#define last(b) ((b)->bk)
|
||
|
||
/*
|
||
Indexing into bins
|
||
*/
|
||
|
||
#define bin_index(sz) \
|
||
(((((unsigned long)(sz)) >> 9) == 0) ? (((unsigned long)(sz)) >> 3): \
|
||
((((unsigned long)(sz)) >> 9) <= 4) ? 56 + (((unsigned long)(sz)) >> 6): \
|
||
((((unsigned long)(sz)) >> 9) <= 20) ? 91 + (((unsigned long)(sz)) >> 9): \
|
||
((((unsigned long)(sz)) >> 9) <= 84) ? 110 + (((unsigned long)(sz)) >> 12): \
|
||
((((unsigned long)(sz)) >> 9) <= 340) ? 119 + (((unsigned long)(sz)) >> 15): \
|
||
((((unsigned long)(sz)) >> 9) <= 1364) ? 124 + (((unsigned long)(sz)) >> 18): \
|
||
126)
|
||
/*
|
||
bins for chunks < 512 are all spaced 8 bytes apart, and hold
|
||
identically sized chunks. This is exploited in malloc.
|
||
*/
|
||
|
||
#define MAX_SMALLBIN 63
|
||
#define MAX_SMALLBIN_SIZE 512
|
||
#define SMALLBIN_WIDTH 8
|
||
|
||
#define smallbin_index(sz) (((unsigned long)(sz)) >> 3)
|
||
|
||
/*
|
||
Requests are `small' if both the corresponding and the next bin are small
|
||
*/
|
||
|
||
#define is_small_request(nb) (nb < MAX_SMALLBIN_SIZE - SMALLBIN_WIDTH)
|
||
|
||
/*
|
||
To help compensate for the large number of bins, a one-level index
|
||
structure is used for bin-by-bin searching. `binblocks' is a
|
||
one-word bitvector recording whether groups of BINBLOCKWIDTH bins
|
||
have any (possibly) non-empty bins, so they can be skipped over
|
||
all at once during during traversals. The bits are NOT always
|
||
cleared as soon as all bins in a block are empty, but instead only
|
||
when all are noticed to be empty during traversal in malloc.
|
||
*/
|
||
|
||
#define BINBLOCKWIDTH 4 /* bins per block */
|
||
|
||
#define binblocks (bin_at(0)->size) /* bitvector of nonempty blocks */
|
||
|
||
/* bin<->block macros */
|
||
|
||
#define idx2binblock(ix) ((unsigned)1 << (ix / BINBLOCKWIDTH))
|
||
#define mark_binblock(ii) (binblocks |= idx2binblock(ii))
|
||
#define clear_binblock(ii) (binblocks &= ~(idx2binblock(ii)))
|
||
|
||
/* ----------------------------------------------------------------------- */
|
||
|
||
/* Other static bookkeeping data */
|
||
|
||
/* variables holding tunable values */
|
||
#ifndef __BAREBOX__
|
||
static unsigned long trim_threshold = DEFAULT_TRIM_THRESHOLD;
|
||
static unsigned int n_mmaps_max = DEFAULT_MMAP_MAX;
|
||
static unsigned long mmap_threshold = DEFAULT_MMAP_THRESHOLD;
|
||
#endif
|
||
static unsigned long top_pad = DEFAULT_TOP_PAD;
|
||
|
||
/* The first value returned from sbrk */
|
||
static char *sbrk_base = (char*)(-1);
|
||
|
||
/* The maximum memory obtained from system via sbrk */
|
||
static unsigned long max_sbrked_mem;
|
||
|
||
/* The maximum via either sbrk or mmap */
|
||
static unsigned long max_total_mem;
|
||
|
||
/* internal working copy of mallinfo */
|
||
static struct mallinfo current_mallinfo;
|
||
|
||
/* The total memory obtained from system via sbrk */
|
||
#define sbrked_mem (current_mallinfo.arena)
|
||
|
||
/* Tracking mmaps */
|
||
|
||
static unsigned long mmapped_mem;
|
||
|
||
/*
|
||
Macro-based internal utilities
|
||
*/
|
||
|
||
|
||
/*
|
||
Linking chunks in bin lists.
|
||
Call these only with variables, not arbitrary expressions, as arguments.
|
||
*/
|
||
|
||
/*
|
||
Place chunk p of size s in its bin, in size order,
|
||
putting it ahead of others of same size.
|
||
*/
|
||
|
||
#define frontlink(P, S, IDX, BK, FD) \
|
||
{ \
|
||
if (S < MAX_SMALLBIN_SIZE) \
|
||
{ \
|
||
IDX = smallbin_index(S); \
|
||
mark_binblock(IDX); \
|
||
BK = bin_at(IDX); \
|
||
FD = BK->fd; \
|
||
P->bk = BK; \
|
||
P->fd = FD; \
|
||
FD->bk = BK->fd = P; \
|
||
} \
|
||
else \
|
||
{ \
|
||
IDX = bin_index(S); \
|
||
BK = bin_at(IDX); \
|
||
FD = BK->fd; \
|
||
if (FD == BK) mark_binblock(IDX); \
|
||
else \
|
||
{ \
|
||
while (FD != BK && S < chunksize(FD)) FD = FD->fd; \
|
||
BK = FD->bk; \
|
||
} \
|
||
P->bk = BK; \
|
||
P->fd = FD; \
|
||
FD->bk = BK->fd = P; \
|
||
} \
|
||
}
|
||
|
||
/* take a chunk off a list */
|
||
|
||
#define unlink(P, BK, FD) \
|
||
{ \
|
||
BK = P->bk; \
|
||
FD = P->fd; \
|
||
FD->bk = BK; \
|
||
BK->fd = FD; \
|
||
} \
|
||
|
||
/* Place p as the last remainder */
|
||
|
||
#define link_last_remainder(P) \
|
||
{ \
|
||
last_remainder->fd = last_remainder->bk = P; \
|
||
P->fd = P->bk = last_remainder; \
|
||
}
|
||
|
||
/* Clear the last_remainder bin */
|
||
|
||
#define clear_last_remainder \
|
||
(last_remainder->fd = last_remainder->bk = last_remainder)
|
||
|
||
/* Routines dealing with mmap(). */
|
||
|
||
/*
|
||
Extend the top-most chunk by obtaining memory from system.
|
||
Main interface to sbrk (but see also malloc_trim).
|
||
*/
|
||
static void malloc_extend_top(INTERNAL_SIZE_T nb)
|
||
{
|
||
char *brk; /* return value from sbrk */
|
||
INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of sbrked space */
|
||
INTERNAL_SIZE_T correction; /* bytes for 2nd sbrk call */
|
||
char *new_brk; /* return of 2nd sbrk call */
|
||
INTERNAL_SIZE_T top_size; /* new size of top chunk */
|
||
|
||
mchunkptr old_top = top; /* Record state of old top */
|
||
INTERNAL_SIZE_T old_top_size = chunksize(old_top);
|
||
char *old_end = (char *) (chunk_at_offset(old_top, old_top_size));
|
||
|
||
/* Pad request with top_pad plus minimal overhead */
|
||
|
||
INTERNAL_SIZE_T sbrk_size = nb + top_pad + MINSIZE;
|
||
unsigned long pagesz = malloc_getpagesize;
|
||
|
||
/* If not the first time through, round to preserve page boundary */
|
||
/* Otherwise, we need to correct to a page size below anyway. */
|
||
/* (We also correct below if an intervening foreign sbrk call.) */
|
||
|
||
if (sbrk_base != (char*)(-1))
|
||
sbrk_size = (sbrk_size + (pagesz - 1)) & ~(pagesz - 1);
|
||
|
||
brk = (char*)(sbrk(sbrk_size));
|
||
|
||
/* Fail if sbrk failed or if a foreign sbrk call killed our space */
|
||
if (brk == (char*)(NULL) || (brk < old_end && old_top != initial_top))
|
||
return;
|
||
|
||
sbrked_mem += sbrk_size;
|
||
|
||
if (brk == old_end) { /* can just add bytes to current top */
|
||
top_size = sbrk_size + old_top_size;
|
||
set_head (top, top_size | PREV_INUSE);
|
||
} else {
|
||
if (sbrk_base == (char*)(-1)) /* First time through. Record base */
|
||
sbrk_base = brk;
|
||
else /* Someone else called sbrk(). Count those bytes as sbrked_mem. */
|
||
sbrked_mem += brk - (char*)old_end;
|
||
|
||
/* Guarantee alignment of first new chunk made from this space */
|
||
front_misalign =
|
||
(unsigned long) chunk2mem(brk) & MALLOC_ALIGN_MASK;
|
||
if (front_misalign > 0) {
|
||
correction = (MALLOC_ALIGNMENT) - front_misalign;
|
||
brk += correction;
|
||
} else
|
||
correction = 0;
|
||
|
||
/* Guarantee the next brk will be at a page boundary */
|
||
|
||
correction += ((((unsigned long) (brk + sbrk_size)) +
|
||
(pagesz - 1)) & ~(pagesz - 1)) -
|
||
((unsigned long) (brk + sbrk_size));
|
||
|
||
/* Allocate correction */
|
||
new_brk = (char*) (sbrk(correction));
|
||
if (new_brk == (char*)(NULL))
|
||
return;
|
||
|
||
sbrked_mem += correction;
|
||
|
||
top = (mchunkptr) brk;
|
||
top_size = new_brk - brk + correction;
|
||
set_head (top, top_size | PREV_INUSE);
|
||
|
||
if (old_top != initial_top) {
|
||
|
||
/* There must have been an intervening foreign sbrk call. */
|
||
/* A double fencepost is necessary to prevent consolidation */
|
||
|
||
/* If not enough space to do this, then user did something very wrong */
|
||
if (old_top_size < MINSIZE) {
|
||
set_head (top, PREV_INUSE); /* will force null return from malloc */
|
||
return;
|
||
}
|
||
|
||
/* Also keep size a multiple of MALLOC_ALIGNMENT */
|
||
old_top_size = (old_top_size -
|
||
3 * SIZE_SZ) & ~MALLOC_ALIGN_MASK;
|
||
set_head_size (old_top, old_top_size);
|
||
chunk_at_offset (old_top, old_top_size)->size =
|
||
SIZE_SZ | PREV_INUSE;
|
||
chunk_at_offset (old_top, old_top_size + SIZE_SZ)->size =
|
||
SIZE_SZ | PREV_INUSE;
|
||
/* If possible, release the rest. */
|
||
if (old_top_size >= MINSIZE)
|
||
free(chunk2mem (old_top));
|
||
}
|
||
}
|
||
|
||
if ((unsigned long) sbrked_mem > (unsigned long) max_sbrked_mem)
|
||
max_sbrked_mem = sbrked_mem;
|
||
if ((unsigned long) (mmapped_mem + sbrked_mem) > (unsigned long) max_total_mem)
|
||
max_total_mem = mmapped_mem + sbrked_mem;
|
||
}
|
||
|
||
/* Main public routines */
|
||
|
||
/*
|
||
Malloc Algorthim:
|
||
|
||
The requested size is first converted into a usable form, `nb'.
|
||
This currently means to add 4 bytes overhead plus possibly more to
|
||
obtain 8-byte alignment and/or to obtain a size of at least
|
||
MINSIZE (currently 16 bytes), the smallest allocatable size.
|
||
(All fits are considered `exact' if they are within MINSIZE bytes.)
|
||
|
||
From there, the first successful of the following steps is taken:
|
||
|
||
1. The bin corresponding to the request size is scanned, and if
|
||
a chunk of exactly the right size is found, it is taken.
|
||
|
||
2. The most recently remaindered chunk is used if it is big
|
||
enough. This is a form of (roving) first fit, used only in
|
||
the absence of exact fits. Runs of consecutive requests use
|
||
the remainder of the chunk used for the previous such request
|
||
whenever possible. This limited use of a first-fit style
|
||
allocation strategy tends to give contiguous chunks
|
||
coextensive lifetimes, which improves locality and can reduce
|
||
fragmentation in the long run.
|
||
|
||
3. Other bins are scanned in increasing size order, using a
|
||
chunk big enough to fulfill the request, and splitting off
|
||
any remainder. This search is strictly by best-fit; i.e.,
|
||
the smallest (with ties going to approximately the least
|
||
recently used) chunk that fits is selected.
|
||
|
||
4. If large enough, the chunk bordering the end of memory
|
||
(`top') is split off. (This use of `top' is in accord with
|
||
the best-fit search rule. In effect, `top' is treated as
|
||
larger (and thus less well fitting) than any other available
|
||
chunk since it can be extended to be as large as necessary
|
||
(up to system limitations).
|
||
|
||
5. If the request size meets the mmap threshold and the
|
||
system supports mmap, and there are few enough currently
|
||
allocated mmapped regions, and a call to mmap succeeds,
|
||
the request is allocated via direct memory mapping.
|
||
|
||
6. Otherwise, the top of memory is extended by
|
||
obtaining more space from the system (normally using sbrk,
|
||
but definable to anything else via the MORECORE macro).
|
||
Memory is gathered from the system (in system page-sized
|
||
units) in a way that allows chunks obtained across different
|
||
sbrk calls to be consolidated, but does not require
|
||
contiguous memory. Thus, it should be safe to intersperse
|
||
mallocs with other sbrk calls.
|
||
|
||
|
||
All allocations are made from the the `lowest' part of any found
|
||
chunk. (The implementation invariant is that prev_inuse is
|
||
always true of any allocated chunk; i.e., that each allocated
|
||
chunk borders either a previously allocated and still in-use chunk,
|
||
or the base of its memory arena.)
|
||
*/
|
||
void *malloc(size_t bytes)
|
||
{
|
||
mchunkptr victim; /* inspected/selected chunk */
|
||
INTERNAL_SIZE_T victim_size; /* its size */
|
||
int idx; /* index for bin traversal */
|
||
mbinptr bin; /* associated bin */
|
||
mchunkptr remainder; /* remainder from a split */
|
||
long remainder_size; /* its size */
|
||
int remainder_index; /* its bin index */
|
||
unsigned long block; /* block traverser bit */
|
||
int startidx; /* first bin of a traversed block */
|
||
mchunkptr fwd; /* misc temp for linking */
|
||
mchunkptr bck; /* misc temp for linking */
|
||
mbinptr q; /* misc temp */
|
||
|
||
INTERNAL_SIZE_T nb;
|
||
|
||
if ((long) bytes < 0)
|
||
return NULL;
|
||
|
||
nb = request2size(bytes); /* padded request size; */
|
||
|
||
/* Check for exact match in a bin */
|
||
|
||
if (is_small_request(nb)) { /* Faster version for small requests */
|
||
idx = smallbin_index(nb);
|
||
|
||
/* No traversal or size check necessary for small bins. */
|
||
|
||
q = bin_at(idx);
|
||
victim = last(q);
|
||
|
||
/* Also scan the next one, since it would have a remainder < MINSIZE */
|
||
if (victim == q) {
|
||
q = next_bin(q);
|
||
victim = last(q);
|
||
}
|
||
if (victim != q) {
|
||
victim_size = chunksize(victim);
|
||
unlink(victim, bck, fwd);
|
||
set_inuse_bit_at_offset(victim, victim_size);
|
||
return chunk2mem(victim);
|
||
}
|
||
idx += 2; /* Set for bin scan below. We've already scanned 2 bins. */
|
||
} else {
|
||
idx = bin_index(nb);
|
||
bin = bin_at(idx);
|
||
|
||
for (victim = last(bin); victim != bin; victim = victim->bk) {
|
||
victim_size = chunksize(victim);
|
||
remainder_size = victim_size - nb;
|
||
|
||
if (remainder_size >= (long)MINSIZE) { /* too big */
|
||
--idx; /* adjust to rescan below after checking last remainder */
|
||
break;
|
||
}
|
||
|
||
else if (remainder_size >= 0) { /* exact fit */
|
||
unlink(victim, bck, fwd);
|
||
set_inuse_bit_at_offset(victim, victim_size);
|
||
return chunk2mem(victim);
|
||
}
|
||
}
|
||
++idx;
|
||
}
|
||
|
||
/* Try to use the last split-off remainder */
|
||
|
||
if ((victim = last_remainder->fd) != last_remainder) {
|
||
victim_size = chunksize(victim);
|
||
remainder_size = victim_size - nb;
|
||
|
||
if (remainder_size >= (long)MINSIZE) { /* re-split */
|
||
remainder = chunk_at_offset(victim, nb);
|
||
set_head(victim, nb | PREV_INUSE);
|
||
link_last_remainder(remainder);
|
||
set_head(remainder, remainder_size | PREV_INUSE);
|
||
set_foot(remainder, remainder_size);
|
||
return chunk2mem(victim);
|
||
}
|
||
|
||
clear_last_remainder;
|
||
|
||
if (remainder_size >= 0) { /* exhaust */
|
||
set_inuse_bit_at_offset(victim, victim_size);
|
||
return chunk2mem(victim);
|
||
}
|
||
/* Else place in bin */
|
||
frontlink(victim, victim_size, remainder_index, bck, fwd);
|
||
}
|
||
|
||
/*
|
||
If there are any possibly nonempty big-enough blocks,
|
||
search for best fitting chunk by scanning bins in blockwidth units.
|
||
*/
|
||
if ((block = idx2binblock (idx)) <= binblocks) {
|
||
/* Get to the first marked block */
|
||
if ((block & binblocks) == 0) {
|
||
/* force to an even block boundary */
|
||
idx = (idx & ~(BINBLOCKWIDTH - 1)) + BINBLOCKWIDTH;
|
||
block <<= 1;
|
||
while ((block & binblocks) == 0) {
|
||
idx += BINBLOCKWIDTH;
|
||
block <<= 1;
|
||
}
|
||
}
|
||
|
||
/* For each possibly nonempty block ... */
|
||
for (;;) {
|
||
startidx = idx; /* (track incomplete blocks) */
|
||
q = bin = bin_at(idx);
|
||
|
||
/* For each bin in this block ... */
|
||
do {
|
||
/* Find and use first big enough chunk ... */
|
||
for (victim = last(bin); victim != bin;
|
||
victim = victim->bk) {
|
||
victim_size = chunksize(victim);
|
||
remainder_size = victim_size - nb;
|
||
|
||
if (remainder_size >= (long)MINSIZE) { /* split */
|
||
remainder =
|
||
chunk_at_offset (victim,
|
||
nb);
|
||
set_head(victim,
|
||
nb | PREV_INUSE);
|
||
unlink(victim, bck, fwd);
|
||
link_last_remainder(remainder);
|
||
set_head(remainder,
|
||
remainder_size |
|
||
PREV_INUSE);
|
||
set_foot(remainder,
|
||
remainder_size);
|
||
return chunk2mem(victim);
|
||
} else if (remainder_size >= 0) { /* take */
|
||
set_inuse_bit_at_offset(victim,
|
||
victim_size);
|
||
unlink(victim, bck, fwd);
|
||
return chunk2mem(victim);
|
||
}
|
||
}
|
||
bin = next_bin (bin);
|
||
} while ((++idx & (BINBLOCKWIDTH - 1)) != 0);
|
||
|
||
/* Clear out the block bit. */
|
||
do { /* Possibly backtrack to try to clear a partial block */
|
||
if ((startidx & (BINBLOCKWIDTH - 1)) == 0) {
|
||
binblocks &= ~block;
|
||
break;
|
||
}
|
||
--startidx;
|
||
q = prev_bin(q);
|
||
} while (first(q) == q);
|
||
|
||
/* Get to the next possibly nonempty block */
|
||
|
||
if ((block <<= 1) <= binblocks && (block != 0)) {
|
||
while ((block & binblocks) == 0) {
|
||
idx += BINBLOCKWIDTH;
|
||
block <<= 1;
|
||
}
|
||
} else
|
||
break;
|
||
}
|
||
}
|
||
|
||
/* Try to use top chunk */
|
||
|
||
/* Require that there be a remainder, ensuring top always exists */
|
||
if ((remainder_size = chunksize (top) - nb) < (long) MINSIZE) {
|
||
/* Try to extend */
|
||
malloc_extend_top(nb);
|
||
if ((remainder_size = chunksize(top) - nb) < (long) MINSIZE)
|
||
return NULL; /* propagate failure */
|
||
}
|
||
|
||
victim = top;
|
||
set_head(victim, nb | PREV_INUSE);
|
||
top = chunk_at_offset(victim, nb);
|
||
set_head(top, remainder_size | PREV_INUSE);
|
||
return chunk2mem(victim);
|
||
}
|
||
|
||
/*
|
||
free() algorithm :
|
||
|
||
cases:
|
||
|
||
1. free(0) has no effect.
|
||
|
||
2. If the chunk was allocated via mmap, it is release via munmap().
|
||
|
||
3. If a returned chunk borders the current high end of memory,
|
||
it is consolidated into the top, and if the total unused
|
||
topmost memory exceeds the trim threshold, malloc_trim is
|
||
called.
|
||
|
||
4. Other chunks are consolidated as they arrive, and
|
||
placed in corresponding bins. (This includes the case of
|
||
consolidating with the current `last_remainder').
|
||
*/
|
||
void free(void *mem)
|
||
{
|
||
mchunkptr p; /* chunk corresponding to mem */
|
||
INTERNAL_SIZE_T hd; /* its head field */
|
||
INTERNAL_SIZE_T sz; /* its size */
|
||
int idx; /* its bin index */
|
||
mchunkptr next; /* next contiguous chunk */
|
||
INTERNAL_SIZE_T nextsz; /* its size */
|
||
INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */
|
||
mchunkptr bck; /* misc temp for linking */
|
||
mchunkptr fwd; /* misc temp for linking */
|
||
int islr; /* track whether merging with last_remainder */
|
||
|
||
if (!mem) /* free(0) has no effect */
|
||
return;
|
||
|
||
p = mem2chunk(mem);
|
||
hd = p->size;
|
||
|
||
|
||
sz = hd & ~PREV_INUSE;
|
||
next = chunk_at_offset(p, sz);
|
||
nextsz = chunksize(next);
|
||
|
||
if (next == top) { /* merge with top */
|
||
sz += nextsz;
|
||
|
||
if (!(hd & PREV_INUSE)) { /* consolidate backward */
|
||
prevsz = p->prev_size;
|
||
p = chunk_at_offset(p, -((long) prevsz));
|
||
sz += prevsz;
|
||
unlink (p, bck, fwd);
|
||
}
|
||
|
||
set_head(p, sz | PREV_INUSE);
|
||
top = p;
|
||
#ifdef USE_MALLOC_TRIM
|
||
if ((unsigned long) (sz) >= (unsigned long)trim_threshold)
|
||
malloc_trim(top_pad);
|
||
#endif
|
||
return;
|
||
}
|
||
|
||
set_head(next, nextsz); /* clear inuse bit */
|
||
|
||
islr = 0;
|
||
|
||
if (!(hd & PREV_INUSE)) { /* consolidate backward */
|
||
prevsz = p->prev_size;
|
||
p = chunk_at_offset(p, -((long) prevsz));
|
||
sz += prevsz;
|
||
|
||
if (p->fd == last_remainder) /* keep as last_remainder */
|
||
islr = 1;
|
||
else
|
||
unlink(p, bck, fwd);
|
||
}
|
||
|
||
if (!(inuse_bit_at_offset(next, nextsz))) { /* consolidate forward */
|
||
sz += nextsz;
|
||
|
||
if (!islr && next->fd == last_remainder) { /* re-insert last_remainder */
|
||
islr = 1;
|
||
link_last_remainder(p);
|
||
} else
|
||
unlink(next, bck, fwd);
|
||
}
|
||
|
||
|
||
set_head(p, sz | PREV_INUSE);
|
||
set_foot(p, sz);
|
||
if (!islr)
|
||
frontlink(p, sz, idx, bck, fwd);
|
||
}
|
||
|
||
/*
|
||
Realloc algorithm:
|
||
|
||
Chunks that were obtained via mmap cannot be extended or shrunk
|
||
unless HAVE_MREMAP is defined, in which case mremap is used.
|
||
Otherwise, if their reallocation is for additional space, they are
|
||
copied. If for less, they are just left alone.
|
||
|
||
Otherwise, if the reallocation is for additional space, and the
|
||
chunk can be extended, it is, else a malloc-copy-free sequence is
|
||
taken. There are several different ways that a chunk could be
|
||
extended. All are tried:
|
||
|
||
* Extending forward into following adjacent free chunk.
|
||
* Shifting backwards, joining preceding adjacent space
|
||
* Both shifting backwards and extending forward.
|
||
* Extending into newly sbrked space
|
||
|
||
Unless the #define REALLOC_ZERO_BYTES_FREES is set, realloc with a
|
||
size argument of zero (re)allocates a minimum-sized chunk.
|
||
|
||
If the reallocation is for less space, and the new request is for
|
||
a `small' (<512 bytes) size, then the newly unused space is lopped
|
||
off and freed.
|
||
|
||
The old unix realloc convention of allowing the last-free'd chunk
|
||
to be used as an argument to realloc is no longer supported.
|
||
I don't know of any programs still relying on this feature,
|
||
and allowing it would also allow too many other incorrect
|
||
usages of realloc to be sensible.
|
||
*/
|
||
void *realloc(void *oldmem, size_t bytes)
|
||
{
|
||
INTERNAL_SIZE_T nb; /* padded request size */
|
||
|
||
mchunkptr oldp; /* chunk corresponding to oldmem */
|
||
INTERNAL_SIZE_T oldsize; /* its size */
|
||
|
||
mchunkptr newp; /* chunk to return */
|
||
INTERNAL_SIZE_T newsize; /* its size */
|
||
void *newmem; /* corresponding user mem */
|
||
|
||
mchunkptr next; /* next contiguous chunk after oldp */
|
||
INTERNAL_SIZE_T nextsize; /* its size */
|
||
|
||
mchunkptr prev; /* previous contiguous chunk before oldp */
|
||
INTERNAL_SIZE_T prevsize; /* its size */
|
||
|
||
mchunkptr remainder; /* holds split off extra space from newp */
|
||
INTERNAL_SIZE_T remainder_size; /* its size */
|
||
|
||
mchunkptr bck; /* misc temp for linking */
|
||
mchunkptr fwd; /* misc temp for linking */
|
||
|
||
#ifdef REALLOC_ZERO_BYTES_FREES
|
||
if (bytes == 0) {
|
||
free(oldmem);
|
||
return NULL;
|
||
}
|
||
#endif
|
||
|
||
if ((long)bytes < 0)
|
||
return NULL;
|
||
|
||
/* realloc of null is supposed to be same as malloc */
|
||
if (!oldmem)
|
||
return malloc(bytes);
|
||
|
||
newp = oldp = mem2chunk(oldmem);
|
||
newsize = oldsize = chunksize(oldp);
|
||
|
||
|
||
nb = request2size(bytes);
|
||
|
||
|
||
if ((long)(oldsize) < (long)(nb)) {
|
||
|
||
/* Try expanding forward */
|
||
|
||
next = chunk_at_offset(oldp, oldsize);
|
||
if (next == top || !inuse(next)) {
|
||
nextsize = chunksize(next);
|
||
|
||
/* Forward into top only if a remainder */
|
||
if (next == top) {
|
||
if ((long)(nextsize + newsize) >=
|
||
(long)(nb + MINSIZE)) {
|
||
newsize += nextsize;
|
||
top = chunk_at_offset(oldp, nb);
|
||
set_head (top,
|
||
(newsize - nb) | PREV_INUSE);
|
||
set_head_size(oldp, nb);
|
||
return chunk2mem(oldp);
|
||
}
|
||
}
|
||
|
||
/* Forward into next chunk */
|
||
else if (((long) (nextsize + newsize) >= (long) (nb))) {
|
||
unlink(next, bck, fwd);
|
||
newsize += nextsize;
|
||
goto split;
|
||
}
|
||
} else {
|
||
next = NULL;
|
||
nextsize = 0;
|
||
}
|
||
|
||
/* Try shifting backwards. */
|
||
|
||
if (!prev_inuse(oldp)) {
|
||
prev = prev_chunk(oldp);
|
||
prevsize = chunksize(prev);
|
||
|
||
/* try forward + backward first to save a later consolidation */
|
||
|
||
if (next) {
|
||
/* into top */
|
||
if (next == top) {
|
||
if ((long)
|
||
(nextsize + prevsize + newsize) >=
|
||
(long)(nb + MINSIZE)) {
|
||
unlink (prev, bck, fwd);
|
||
newp = prev;
|
||
newsize += prevsize + nextsize;
|
||
newmem = chunk2mem(newp);
|
||
memcpy(newmem, oldmem,
|
||
oldsize - SIZE_SZ);
|
||
top = chunk_at_offset(newp, nb);
|
||
set_head(top,
|
||
(newsize -
|
||
nb) | PREV_INUSE);
|
||
set_head_size(newp, nb);
|
||
return newmem;
|
||
}
|
||
}
|
||
|
||
/* into next chunk */
|
||
else if (((long)(nextsize + prevsize + newsize)
|
||
>= (long)(nb))) {
|
||
unlink(next, bck, fwd);
|
||
unlink(prev, bck, fwd);
|
||
newp = prev;
|
||
newsize += nextsize + prevsize;
|
||
newmem = chunk2mem(newp);
|
||
memcpy(newmem, oldmem,
|
||
oldsize - SIZE_SZ);
|
||
goto split;
|
||
}
|
||
}
|
||
|
||
/* backward only */
|
||
if (prev && (long)(prevsize + newsize) >= (long)nb) {
|
||
unlink(prev, bck, fwd);
|
||
newp = prev;
|
||
newsize += prevsize;
|
||
newmem = chunk2mem(newp);
|
||
memcpy(newmem, oldmem, oldsize - SIZE_SZ);
|
||
goto split;
|
||
}
|
||
}
|
||
|
||
/* Must allocate */
|
||
|
||
newmem = malloc(bytes);
|
||
|
||
if (!newmem) /* propagate failure */
|
||
return NULL;
|
||
|
||
/* Avoid copy if newp is next chunk after oldp. */
|
||
/* (This can only happen when new chunk is sbrk'ed.) */
|
||
|
||
if ((newp = mem2chunk(newmem)) == next_chunk(oldp)) {
|
||
newsize += chunksize(newp);
|
||
newp = oldp;
|
||
goto split;
|
||
}
|
||
|
||
/* Otherwise copy, free, and exit */
|
||
memcpy(newmem, oldmem, oldsize - SIZE_SZ);
|
||
free(oldmem);
|
||
return newmem;
|
||
}
|
||
|
||
|
||
split: /* split off extra room in old or expanded chunk */
|
||
|
||
if (newsize - nb >= MINSIZE) { /* split off remainder */
|
||
remainder = chunk_at_offset(newp, nb);
|
||
remainder_size = newsize - nb;
|
||
set_head_size(newp, nb);
|
||
set_head(remainder, remainder_size | PREV_INUSE);
|
||
set_inuse_bit_at_offset(remainder, remainder_size);
|
||
free (chunk2mem(remainder)); /* let free() deal with it */
|
||
} else {
|
||
set_head_size(newp, newsize);
|
||
set_inuse_bit_at_offset(newp, newsize);
|
||
}
|
||
|
||
return chunk2mem(newp);
|
||
}
|
||
|
||
/*
|
||
memalign algorithm:
|
||
|
||
memalign requests more than enough space from malloc, finds a spot
|
||
within that chunk that meets the alignment request, and then
|
||
possibly frees the leading and trailing space.
|
||
|
||
The alignment argument must be a power of two. This property is not
|
||
checked by memalign, so misuse may result in random runtime errors.
|
||
|
||
8-byte alignment is guaranteed by normal malloc calls, so don't
|
||
bother calling memalign with an argument of 8 or less.
|
||
|
||
Overreliance on memalign is a sure way to fragment space.
|
||
*/
|
||
void *memalign(size_t alignment, size_t bytes)
|
||
{
|
||
INTERNAL_SIZE_T nb; /* padded request size */
|
||
char *m; /* memory returned by malloc call */
|
||
mchunkptr p; /* corresponding chunk */
|
||
char *brk; /* alignment point within p */
|
||
mchunkptr newp; /* chunk to return */
|
||
INTERNAL_SIZE_T newsize; /* its size */
|
||
INTERNAL_SIZE_T leadsize; /* leading space befor alignment point */
|
||
mchunkptr remainder; /* spare room at end to split off */
|
||
long remainder_size; /* its size */
|
||
|
||
if ((long) bytes < 0)
|
||
return NULL;
|
||
|
||
/* If need less alignment than we give anyway, just relay to malloc */
|
||
|
||
if (alignment <= MALLOC_ALIGNMENT)
|
||
return malloc(bytes);
|
||
|
||
/* Otherwise, ensure that it is at least a minimum chunk size */
|
||
|
||
if (alignment < MINSIZE)
|
||
alignment = MINSIZE;
|
||
|
||
/* Call malloc with worst case padding to hit alignment. */
|
||
|
||
nb = request2size(bytes);
|
||
m = (char*)(malloc (nb + alignment + MINSIZE));
|
||
|
||
if (!m)
|
||
return NULL; /* propagate failure */
|
||
|
||
p = mem2chunk(m);
|
||
|
||
if ((((unsigned long)(m)) % alignment) == 0) { /* aligned */
|
||
} else { /* misaligned */
|
||
|
||
/*
|
||
Find an aligned spot inside chunk.
|
||
Since we need to give back leading space in a chunk of at
|
||
least MINSIZE, if the first calculation places us at
|
||
a spot with less than MINSIZE leader, we can move to the
|
||
next aligned spot -- we've allocated enough total room so that
|
||
this is always possible.
|
||
*/
|
||
|
||
brk = (char*) mem2chunk(((unsigned long) (m + alignment - 1)) &
|
||
-((signed) alignment));
|
||
if ((long)(brk - (char*)(p)) < MINSIZE)
|
||
brk = brk + alignment;
|
||
|
||
newp = (mchunkptr)brk;
|
||
leadsize = brk - (char*)(p);
|
||
newsize = chunksize(p) - leadsize;
|
||
|
||
/* give back leader, use the rest */
|
||
|
||
set_head(newp, newsize | PREV_INUSE);
|
||
set_inuse_bit_at_offset(newp, newsize);
|
||
set_head_size(p, leadsize);
|
||
free(chunk2mem(p));
|
||
p = newp;
|
||
}
|
||
|
||
/* Also give back spare room at the end */
|
||
|
||
remainder_size = chunksize(p) - nb;
|
||
|
||
if (remainder_size >= (long)MINSIZE) {
|
||
remainder = chunk_at_offset(p, nb);
|
||
set_head(remainder, remainder_size | PREV_INUSE);
|
||
set_head_size(p, nb);
|
||
free (chunk2mem(remainder));
|
||
}
|
||
|
||
return chunk2mem(p);
|
||
}
|
||
|
||
#if 0
|
||
/*
|
||
* valloc just invokes memalign with alignment argument equal
|
||
* to the page size of the system (or as near to this as can
|
||
* be figured out from all the includes/defines above.)
|
||
*/
|
||
void *valloc(size_t bytes)
|
||
{
|
||
return memalign(malloc_getpagesize, bytes);
|
||
}
|
||
#endif
|
||
|
||
/*
|
||
* pvalloc just invokes valloc for the nearest pagesize
|
||
* that will accommodate request
|
||
*/
|
||
void *pvalloc (size_t bytes)
|
||
{
|
||
size_t pagesize = malloc_getpagesize;
|
||
|
||
return memalign(pagesize, (bytes + pagesize - 1) & ~(pagesize - 1));
|
||
}
|
||
|
||
/*
|
||
*
|
||
* calloc calls malloc, then zeroes out the allocated chunk.
|
||
*
|
||
*/
|
||
void *calloc(size_t n, size_t elem_size)
|
||
{
|
||
mchunkptr p;
|
||
INTERNAL_SIZE_T csz;
|
||
INTERNAL_SIZE_T sz = n * elem_size;
|
||
|
||
/* check if expand_top called, in which case don't need to clear */
|
||
mchunkptr oldtop = top;
|
||
INTERNAL_SIZE_T oldtopsize = chunksize(top);
|
||
|
||
void *mem = malloc(sz);
|
||
|
||
if ((long)n < 0)
|
||
return NULL;
|
||
|
||
if (!mem)
|
||
return NULL;
|
||
else {
|
||
p = mem2chunk(mem);
|
||
|
||
/* Two optional cases in which clearing not necessary */
|
||
csz = chunksize(p);
|
||
|
||
if (p == oldtop && csz > oldtopsize) {
|
||
/* clear only the bytes from non-freshly-sbrked memory */
|
||
csz = oldtopsize;
|
||
}
|
||
|
||
memset(mem, 0, csz - SIZE_SZ);
|
||
return mem;
|
||
}
|
||
}
|
||
|
||
/*
|
||
*
|
||
* cfree just calls free. It is needed/defined on some systems
|
||
* that pair it with calloc, presumably for odd historical reasons.
|
||
*/
|
||
#if !defined(INTERNAL_LINUX_C_LIB) || !defined(__ELF__)
|
||
void cfree(void *mem)
|
||
{
|
||
free(mem);
|
||
}
|
||
#endif
|
||
|
||
/*
|
||
Malloc_trim gives memory back to the system (via negative
|
||
arguments to sbrk) if there is unused memory at the `high' end of
|
||
the malloc pool. You can call this after freeing large blocks of
|
||
memory to potentially reduce the system-level memory requirements
|
||
of a program. However, it cannot guarantee to reduce memory. Under
|
||
some allocation patterns, some large free blocks of memory will be
|
||
locked between two used chunks, so they cannot be given back to
|
||
the system.
|
||
|
||
The `pad' argument to malloc_trim represents the amount of free
|
||
trailing space to leave untrimmed. If this argument is zero,
|
||
only the minimum amount of memory to maintain internal data
|
||
structures will be left (one page or less). Non-zero arguments
|
||
can be supplied to maintain enough trailing space to service
|
||
future expected allocations without having to re-obtain memory
|
||
from the system.
|
||
|
||
Malloc_trim returns 1 if it actually released any memory, else 0.
|
||
*/
|
||
#ifdef USE_MALLOC_TRIM
|
||
int malloc_trim(size_t pad)
|
||
{
|
||
long top_size; /* Amount of top-most memory */
|
||
long extra; /* Amount to release */
|
||
char *current_brk; /* address returned by pre-check sbrk call */
|
||
char *new_brk; /* address returned by negative sbrk call */
|
||
|
||
unsigned long pagesz = malloc_getpagesize;
|
||
|
||
top_size = chunksize(top);
|
||
extra = ((top_size - pad - MINSIZE + (pagesz - 1)) / pagesz -
|
||
1) * pagesz;
|
||
|
||
if (extra < (long)pagesz) /* Not enough memory to release */
|
||
return 0;
|
||
|
||
else {
|
||
/* Test to make sure no one else called sbrk */
|
||
current_brk = (char*)(sbrk(0));
|
||
if (current_brk != (char*)(top) + top_size)
|
||
return 0; /* Apparently we don't own memory; must fail */
|
||
|
||
else {
|
||
new_brk = (char *) (sbrk(-extra));
|
||
|
||
if (new_brk == (char*)(NULL)) { /* sbrk failed? */
|
||
/* Try to figure out what we have */
|
||
current_brk = (char*)(sbrk (0));
|
||
top_size = current_brk - (char*) top;
|
||
if (top_size >= (long)MINSIZE) { /* if not, we are very very dead! */
|
||
sbrked_mem = current_brk - sbrk_base;
|
||
set_head(top, top_size | PREV_INUSE);
|
||
}
|
||
return 0;
|
||
}
|
||
|
||
else {
|
||
/* Success. Adjust top accordingly. */
|
||
set_head(top, (top_size - extra) | PREV_INUSE);
|
||
sbrked_mem -= extra;
|
||
return 1;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
#endif
|
||
|
||
/*
|
||
* malloc_usable_size:
|
||
*
|
||
* This routine tells you how many bytes you can actually use in an
|
||
* allocated chunk, which may be more than you requested (although
|
||
* often not). You can use this many bytes without worrying about
|
||
* overwriting other allocated objects. Not a particularly great
|
||
* programming practice, but still sometimes useful.
|
||
*/
|
||
size_t malloc_usable_size(void *mem)
|
||
{
|
||
mchunkptr p;
|
||
|
||
if (!mem)
|
||
return 0;
|
||
else {
|
||
p = mem2chunk(mem);
|
||
if (!chunk_is_mmapped(p)) {
|
||
if (!inuse(p))
|
||
return 0;
|
||
return chunksize(p) - SIZE_SZ;
|
||
}
|
||
return chunksize(p) - 2 * SIZE_SZ;
|
||
}
|
||
}
|
||
|
||
|
||
|
||
|
||
/* Utility to update current_mallinfo for malloc_stats and mallinfo() */
|
||
|
||
#ifdef CONFIG_CMD_MEMINFO
|
||
static void malloc_update_mallinfo(void)
|
||
{
|
||
int i;
|
||
mbinptr b;
|
||
mchunkptr p;
|
||
|
||
#ifdef DEBUG
|
||
mchunkptr q;
|
||
#endif
|
||
|
||
INTERNAL_SIZE_T avail = chunksize(top);
|
||
int navail = ((long)(avail) >= (long)MINSIZE) ? 1 : 0;
|
||
|
||
for (i = 1; i < NAV; ++i) {
|
||
b = bin_at (i);
|
||
for (p = last(b); p != b; p = p->bk) {
|
||
#ifdef DEBUG
|
||
for (q = next_chunk(p);
|
||
q < top && inuse(q)
|
||
&& (long) (chunksize(q)) >= (long)MINSIZE;
|
||
q = next_chunk(q))
|
||
#endif
|
||
avail += chunksize(p);
|
||
navail++;
|
||
}
|
||
}
|
||
|
||
current_mallinfo.ordblks = navail;
|
||
current_mallinfo.uordblks = sbrked_mem - avail;
|
||
current_mallinfo.fordblks = avail;
|
||
#if HAVE_MMAP
|
||
current_mallinfo.hblks = n_mmaps;
|
||
#endif
|
||
current_mallinfo.hblkhd = mmapped_mem;
|
||
current_mallinfo.keepcost = chunksize(top);
|
||
|
||
}
|
||
|
||
/*
|
||
malloc_stats:
|
||
|
||
Prints on the amount of space obtain from the system (both
|
||
via sbrk and mmap), the maximum amount (which may be more than
|
||
current if malloc_trim and/or munmap got called), the maximum
|
||
number of simultaneous mmap regions used, and the current number
|
||
of bytes allocated via malloc (or realloc, etc) but not yet
|
||
freed. (Note that this is the number of bytes allocated, not the
|
||
number requested. It will be larger than the number requested
|
||
because of alignment and bookkeeping overhead.)
|
||
*/
|
||
/*
|
||
* mallinfo returns a copy of updated current mallinfo.
|
||
*/
|
||
void malloc_stats(void)
|
||
{
|
||
malloc_update_mallinfo();
|
||
printf("max system bytes = %10u\n", (unsigned int)(max_total_mem));
|
||
printf("system bytes = %10u\n",
|
||
(unsigned int)(sbrked_mem + mmapped_mem));
|
||
printf("in use bytes = %10u\n",
|
||
(unsigned int)(current_mallinfo.uordblks + mmapped_mem));
|
||
#if HAVE_MMAP
|
||
fprintf(stderr, "max mmap regions = %10u\n",
|
||
(unsigned int) max_n_mmaps);
|
||
#endif
|
||
}
|
||
|
||
#endif /* CONFIG_CMD_MEMINFO */
|
||
|
||
/*
|
||
mallopt:
|
||
|
||
mallopt is the general SVID/XPG interface to tunable parameters.
|
||
The format is to provide a (parameter-number, parameter-value) pair.
|
||
mallopt then sets the corresponding parameter to the argument
|
||
value if it can (i.e., so long as the value is meaningful),
|
||
and returns 1 if successful else 0.
|
||
|
||
See descriptions of tunable parameters above.
|
||
*/
|
||
#ifndef __BAREBOX__
|
||
int mallopt(int param_number, int value)
|
||
{
|
||
switch (param_number) {
|
||
case M_TRIM_THRESHOLD:
|
||
trim_threshold = value;
|
||
return 1;
|
||
case M_TOP_PAD:
|
||
top_pad = value;
|
||
return 1;
|
||
case M_MMAP_THRESHOLD:
|
||
mmap_threshold = value;
|
||
return 1;
|
||
case M_MMAP_MAX:
|
||
if (value != 0)
|
||
return 0;
|
||
else
|
||
n_mmaps_max = value;
|
||
return 1;
|
||
|
||
default:
|
||
return 0;
|
||
}
|
||
}
|
||
#endif
|
||
|
||
/*
|
||
|
||
History:
|
||
|
||
V2.6.6 Sun Dec 5 07:42:19 1999 Doug Lea (dl at gee)
|
||
* return null for negative arguments
|
||
* Added Several WIN32 cleanups from Martin C. Fong <mcfong@yahoo.com>
|
||
* Add 'LACKS_SYS_PARAM_H' for those systems without 'sys/param.h'
|
||
(e.g. WIN32 platforms)
|
||
* Cleanup up header file inclusion for WIN32 platforms
|
||
* Cleanup code to avoid Microsoft Visual C++ compiler complaints
|
||
* Add 'USE_DL_PREFIX' to quickly allow co-existence with existing
|
||
memory allocation routines
|
||
* Set 'malloc_getpagesize' for WIN32 platforms (needs more work)
|
||
* Use 'assert' rather than 'ASSERT' in WIN32 code to conform to
|
||
usage of 'assert' in non-WIN32 code
|
||
* Improve WIN32 'sbrk()' emulation's 'findRegion()' routine to
|
||
avoid infinite loop
|
||
* Always call 'fREe()' rather than 'free()'
|
||
|
||
V2.6.5 Wed Jun 17 15:57:31 1998 Doug Lea (dl at gee)
|
||
* Fixed ordering problem with boundary-stamping
|
||
|
||
V2.6.3 Sun May 19 08:17:58 1996 Doug Lea (dl at gee)
|
||
* Added pvalloc, as recommended by H.J. Liu
|
||
* Added 64bit pointer support mainly from Wolfram Gloger
|
||
* Added anonymously donated WIN32 sbrk emulation
|
||
* Malloc, calloc, getpagesize: add optimizations from Raymond Nijssen
|
||
* malloc_extend_top: fix mask error that caused wastage after
|
||
foreign sbrks
|
||
* Add linux mremap support code from HJ Liu
|
||
|
||
V2.6.2 Tue Dec 5 06:52:55 1995 Doug Lea (dl at gee)
|
||
* Integrated most documentation with the code.
|
||
* Add support for mmap, with help from
|
||
Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
|
||
* Use last_remainder in more cases.
|
||
* Pack bins using idea from colin@nyx10.cs.du.edu
|
||
* Use ordered bins instead of best-fit threshhold
|
||
* Eliminate block-local decls to simplify tracing and debugging.
|
||
* Support another case of realloc via move into top
|
||
* Fix error occuring when initial sbrk_base not word-aligned.
|
||
* Rely on page size for units instead of SBRK_UNIT to
|
||
avoid surprises about sbrk alignment conventions.
|
||
* Add mallinfo, mallopt. Thanks to Raymond Nijssen
|
||
(raymond@es.ele.tue.nl) for the suggestion.
|
||
* Add `pad' argument to malloc_trim and top_pad mallopt parameter.
|
||
* More precautions for cases where other routines call sbrk,
|
||
courtesy of Wolfram Gloger (Gloger@lrz.uni-muenchen.de).
|
||
* Added macros etc., allowing use in linux libc from
|
||
H.J. Lu (hjl@gnu.ai.mit.edu)
|
||
* Inverted this history list
|
||
|
||
V2.6.1 Sat Dec 2 14:10:57 1995 Doug Lea (dl at gee)
|
||
* Re-tuned and fixed to behave more nicely with V2.6.0 changes.
|
||
* Removed all preallocation code since under current scheme
|
||
the work required to undo bad preallocations exceeds
|
||
the work saved in good cases for most test programs.
|
||
* No longer use return list or unconsolidated bins since
|
||
no scheme using them consistently outperforms those that don't
|
||
given above changes.
|
||
* Use best fit for very large chunks to prevent some worst-cases.
|
||
* Added some support for debugging
|
||
|
||
V2.6.0 Sat Nov 4 07:05:23 1995 Doug Lea (dl at gee)
|
||
* Removed footers when chunks are in use. Thanks to
|
||
Paul Wilson (wilson@cs.texas.edu) for the suggestion.
|
||
|
||
V2.5.4 Wed Nov 1 07:54:51 1995 Doug Lea (dl at gee)
|
||
* Added malloc_trim, with help from Wolfram Gloger
|
||
(wmglo@Dent.MED.Uni-Muenchen.DE).
|
||
|
||
V2.5.3 Tue Apr 26 10:16:01 1994 Doug Lea (dl at g)
|
||
|
||
V2.5.2 Tue Apr 5 16:20:40 1994 Doug Lea (dl at g)
|
||
* realloc: try to expand in both directions
|
||
* malloc: swap order of clean-bin strategy;
|
||
* realloc: only conditionally expand backwards
|
||
* Try not to scavenge used bins
|
||
* Use bin counts as a guide to preallocation
|
||
* Occasionally bin return list chunks in first scan
|
||
* Add a few optimizations from colin@nyx10.cs.du.edu
|
||
|
||
V2.5.1 Sat Aug 14 15:40:43 1993 Doug Lea (dl at g)
|
||
* faster bin computation & slightly different binning
|
||
* merged all consolidations to one part of malloc proper
|
||
(eliminating old malloc_find_space & malloc_clean_bin)
|
||
* Scan 2 returns chunks (not just 1)
|
||
* Propagate failure in realloc if malloc returns 0
|
||
* Add stuff to allow compilation on non-ANSI compilers
|
||
from kpv@research.att.com
|
||
|
||
V2.5 Sat Aug 7 07:41:59 1993 Doug Lea (dl at g.oswego.edu)
|
||
* removed potential for odd address access in prev_chunk
|
||
* removed dependency on getpagesize.h
|
||
* misc cosmetics and a bit more internal documentation
|
||
* anticosmetics: mangled names in macros to evade debugger strangeness
|
||
* tested on sparc, hp-700, dec-mips, rs6000
|
||
with gcc & native cc (hp, dec only) allowing
|
||
Detlefs & Zorn comparison study (in SIGPLAN Notices.)
|
||
|
||
Trial version Fri Aug 28 13:14:29 1992 Doug Lea (dl at g.oswego.edu)
|
||
* Based loosely on libg++-1.2X malloc. (It retains some of the overall
|
||
structure of old version, but most details differ.)
|
||
|
||
*/
|
||
|
||
EXPORT_SYMBOL(malloc);
|
||
EXPORT_SYMBOL(calloc);
|
||
EXPORT_SYMBOL(free);
|
||
EXPORT_SYMBOL(realloc);
|