mirror of git://git.sysmocom.de/ofono
PPP: Optimize write buffer management
Extend the write buffer handling in gathdlc.c to minimize stalling and process switching during large PPP transfers. The single write buffer is replaced by a queue of buffers, allowing for much larger emission windows without hugely impacting memory consumption. This reduces the time required to send 50 MB between a couple of local PPP interfaces on my laptop from ~53s to ~3s.
This commit is contained in:
Patrick Porlan
Denis Kenzior
parent
a9f75b3f23
commit
bb0e3e0a58
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@ -37,7 +37,9 @@
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#include "gatio.h"
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#include "gathdlc.h"
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#define BUFFER_SIZE 2048
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#define BUFFER_SIZE (2 * 2048)
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#define MAX_BUFFERS 64 /* Maximum number of in-flight write buffers */
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#define HDLC_OVERHEAD 256 /* Rough estimate of HDLC protocol overhead */
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#define HDLC_FLAG 0x7e /* Flag sequence */
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#define HDLC_ESCAPE 0x7d /* Asynchronous control escape */
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@ -51,7 +53,7 @@
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struct _GAtHDLC {
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gint ref_count;
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GAtIO *io;
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struct ring_buffer *write_buffer;
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GQueue *write_queue; /* Write buffer queue */
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unsigned char *decode_buffer;
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guint decode_offset;
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guint16 decode_fcs;
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@ -201,6 +203,7 @@ GAtHDLC *g_at_hdlc_new_from_io(GAtIO *io)
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{
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GAtHDLC *hdlc;
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unsigned char *buf;
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struct ring_buffer* write_buffer;
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if (io == NULL)
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return NULL;
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@ -218,16 +221,22 @@ GAtHDLC *g_at_hdlc_new_from_io(GAtIO *io)
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hdlc->xmit_accm[3] = 0x60000000; /* 0x7d, 0x7e */
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hdlc->recv_accm = ~0U;
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hdlc->write_buffer = ring_buffer_new(BUFFER_SIZE * 2);
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if (!hdlc->write_buffer)
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write_buffer = ring_buffer_new(BUFFER_SIZE);
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if (!write_buffer)
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goto error;
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/* Write an initial 0x7e as wakeup character */
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buf = ring_buffer_write_ptr(hdlc->write_buffer, 0);
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*buf = HDLC_FLAG;
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ring_buffer_write_advance(hdlc->write_buffer, 1);
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hdlc->write_queue = g_queue_new();
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if (!hdlc->write_queue)
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goto error;
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hdlc->decode_buffer = g_try_malloc(BUFFER_SIZE * 2);
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g_queue_push_tail(hdlc->write_queue, write_buffer);
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/* Write an initial 0x7e as wakeup character */
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buf = ring_buffer_write_ptr(write_buffer, 0);
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*buf = HDLC_FLAG;
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ring_buffer_write_advance(write_buffer, 1);
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hdlc->decode_buffer = g_try_malloc(BUFFER_SIZE);
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if (!hdlc->decode_buffer)
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goto error;
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@ -239,8 +248,11 @@ GAtHDLC *g_at_hdlc_new_from_io(GAtIO *io)
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return hdlc;
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error:
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if (hdlc->write_buffer)
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ring_buffer_free(hdlc->write_buffer);
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if (hdlc->write_queue)
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g_queue_free(hdlc->write_queue);
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if (write_buffer)
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ring_buffer_free(write_buffer);
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if (hdlc->decode_buffer)
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g_free(hdlc->decode_buffer);
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@ -277,6 +289,8 @@ GAtHDLC *g_at_hdlc_ref(GAtHDLC *hdlc)
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void g_at_hdlc_unref(GAtHDLC *hdlc)
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{
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struct ring_buffer *write_buffer;
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if (hdlc == NULL)
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return;
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@ -294,7 +308,11 @@ void g_at_hdlc_unref(GAtHDLC *hdlc)
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g_at_io_unref(hdlc->io);
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hdlc->io = NULL;
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ring_buffer_free(hdlc->write_buffer);
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while ((write_buffer = g_queue_pop_head(hdlc->write_queue)))
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ring_buffer_free(write_buffer);
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g_queue_free(hdlc->write_queue);
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g_free(hdlc->decode_buffer);
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if (hdlc->in_read_handler)
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@ -328,15 +346,32 @@ static gboolean can_write_data(gpointer data)
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unsigned int len;
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unsigned char *buf;
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gsize bytes_written;
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struct ring_buffer* write_buffer;
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len = ring_buffer_len_no_wrap(hdlc->write_buffer);
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buf = ring_buffer_read_ptr(hdlc->write_buffer, 0);
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/* Write data out from the head of the queue */
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write_buffer = g_queue_peek_head(hdlc->write_queue);
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len = ring_buffer_len_no_wrap(write_buffer);
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buf = ring_buffer_read_ptr(write_buffer, 0);
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bytes_written = g_at_io_write(hdlc->io, (gchar *) buf, len);
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hdlc_record(hdlc->record_fd, FALSE, buf, bytes_written);
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ring_buffer_drain(hdlc->write_buffer, bytes_written);
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ring_buffer_drain(write_buffer, bytes_written);
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if (ring_buffer_len(hdlc->write_buffer) > 0)
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if (ring_buffer_len(write_buffer) > 0)
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return TRUE;
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/* All data in current buffer is written, free it
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* unless it's the last buffer in the queue.
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*/
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if ((ring_buffer_len(write_buffer) == 0) &&
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(g_queue_get_length(hdlc->write_queue) > 1)) {
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write_buffer = g_queue_pop_head(hdlc->write_queue);
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ring_buffer_free(write_buffer);
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write_buffer = g_queue_peek_head(hdlc->write_queue);
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}
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if (ring_buffer_len(write_buffer) > 0)
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return TRUE;
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return FALSE;
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@ -370,19 +405,33 @@ GAtIO *g_at_hdlc_get_io(GAtHDLC *hdlc)
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gboolean g_at_hdlc_send(GAtHDLC *hdlc, const unsigned char *data, gsize size)
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{
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unsigned int avail = ring_buffer_avail(hdlc->write_buffer);
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unsigned int wrap = ring_buffer_avail_no_wrap(hdlc->write_buffer);
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unsigned char *buf = ring_buffer_write_ptr(hdlc->write_buffer, 0);
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struct ring_buffer* write_buffer = g_queue_peek_tail(hdlc->write_queue);
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unsigned int avail = ring_buffer_avail(write_buffer);
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unsigned int wrap = ring_buffer_avail_no_wrap(write_buffer);
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unsigned char *buf;
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unsigned char tail[2];
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unsigned int i = 0;
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guint16 fcs = HDLC_INITFCS;
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gboolean escape = FALSE;
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gsize pos = 0;
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if (avail < size)
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return FALSE;
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if (avail < size + HDLC_OVERHEAD) {
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if (g_queue_get_length(hdlc->write_queue) > MAX_BUFFERS)
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return FALSE; /* Too many pending buffers */
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write_buffer = ring_buffer_new(BUFFER_SIZE);
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if (write_buffer == NULL)
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return FALSE;
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g_queue_push_tail(hdlc->write_queue, write_buffer);
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avail = ring_buffer_avail(write_buffer);
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wrap = ring_buffer_avail_no_wrap(write_buffer);
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}
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i = 0;
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buf = ring_buffer_write_ptr(write_buffer, 0);
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while (pos < avail && i < size) {
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if (escape == TRUE) {
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@ -401,7 +450,7 @@ gboolean g_at_hdlc_send(GAtHDLC *hdlc, const unsigned char *data, gsize size)
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pos++;
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if (pos == wrap)
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buf = ring_buffer_write_ptr(hdlc->write_buffer, pos);
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buf = ring_buffer_write_ptr(write_buffer, pos);
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}
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if (i < size)
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@ -428,7 +477,7 @@ gboolean g_at_hdlc_send(GAtHDLC *hdlc, const unsigned char *data, gsize size)
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pos++;
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if (pos == wrap)
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buf = ring_buffer_write_ptr(hdlc->write_buffer, pos);
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buf = ring_buffer_write_ptr(write_buffer, pos);
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}
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if (i < sizeof(tail))
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@ -440,7 +489,7 @@ gboolean g_at_hdlc_send(GAtHDLC *hdlc, const unsigned char *data, gsize size)
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*buf = HDLC_FLAG;
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pos++;
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ring_buffer_write_advance(hdlc->write_buffer, pos);
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ring_buffer_write_advance(write_buffer, pos);
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g_at_io_set_write_handler(hdlc->io, can_write_data, hdlc);
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