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core: Use eventfd for alert pipes on Linux when possible

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The primary win of switching to eventfd when possible is that it only
uses a single file descriptor while pipe() will use two. This means for
each bridge channel we're reducing the number of required file
descriptors by 1, and - if you're using timerfd - we also now have 1
less file descriptor per Asterisk channel.

The API is not ideal (passing int arrays), but this is the cleanest
approach I could come up with to maintain API/ABI.

I've also removed what I believe to be an erroneous code block that
checked the non-blocking flag on the pipe ends for each read. If the
file descriptor is 'losing' its non-blocking mode, it is because of a
bug somewhere else in our code.

In my testing I haven't seen any measurable difference in performance.

Change-Id: Iff0fb1573e7f7a187d5211ddc60aa8f3da3edb1d
This commit is contained in:
Sean Bright
2017-04-17 20:06:10 -04:00
parent dac4442cdd
commit cea3742c54
9 changed files with 412 additions and 203 deletions
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87
main/bridge_channel.c
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@@ -37,6 +37,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
#include <signal.h>
#include "asterisk/heap.h"
#include "asterisk/alertpipe.h"
#include "asterisk/astobj2.h"
#include "asterisk/stringfields.h"
#include "asterisk/app.h"
@@ -956,7 +957,6 @@ static void bridge_frame_free(struct ast_frame *frame)
int ast_bridge_channel_queue_frame(struct ast_bridge_channel *bridge_channel, struct ast_frame *fr)
{
struct ast_frame *dup;
char nudge = 0;
if (bridge_channel->suspended
/* Also defer DTMF frames. */
@@ -985,7 +985,7 @@ int ast_bridge_channel_queue_frame(struct ast_bridge_channel *bridge_channel, st
}
AST_LIST_INSERT_TAIL(&bridge_channel->wr_queue, dup, frame_list);
if (write(bridge_channel->alert_pipe[1], &nudge, sizeof(nudge)) != sizeof(nudge)) {
if (ast_alertpipe_write(bridge_channel->alert_pipe)) {
ast_log(LOG_ERROR, "We couldn't write alert pipe for %p(%s)... something is VERY wrong\n",
bridge_channel, ast_channel_name(bridge_channel->chan));
}
@@ -2257,25 +2257,6 @@ static void bridge_channel_handle_control(struct ast_bridge_channel *bridge_chan
}
}
/*!
* \internal
* \param bridge_channel Channel to read wr_queue alert pipe.
*
* \return Nothing
*/
static void bridge_channel_read_wr_queue_alert(struct ast_bridge_channel *bridge_channel)
{
char nudge;
if (read(bridge_channel->alert_pipe[0], &nudge, sizeof(nudge)) < 0) {
if (errno != EINTR && errno != EAGAIN) {
ast_log(LOG_WARNING, "read() failed for alert pipe on %p(%s): %s\n",
bridge_channel, ast_channel_name(bridge_channel->chan),
strerror(errno));
}
}
}
/*!
* \internal
* \brief Handle bridge channel write frame to channel.
@@ -2298,7 +2279,7 @@ static void bridge_channel_handle_write(struct ast_bridge_channel *bridge_channe
/* No frame, flush the alert pipe of excess alerts. */
ast_log(LOG_WARNING, "Weird. No frame from bridge for %s to process?\n",
ast_channel_name(bridge_channel->chan));
bridge_channel_read_wr_queue_alert(bridge_channel);
ast_alertpipe_read(bridge_channel->alert_pipe);
ast_bridge_channel_unlock(bridge_channel);
return;
}
@@ -2314,7 +2295,7 @@ static void bridge_channel_handle_write(struct ast_bridge_channel *bridge_channe
break;
}
}
bridge_channel_read_wr_queue_alert(bridge_channel);
ast_alertpipe_read(bridge_channel->alert_pipe);
AST_LIST_REMOVE_CURRENT(frame_list);
break;
}
@@ -2852,62 +2833,6 @@ int bridge_channel_internal_allows_optimization(struct ast_bridge_channel *bridg
&& AST_LIST_EMPTY(&bridge_channel->wr_queue);
}
/*!
* \internal
* \brief Close a pipe.
* \since 12.0.0
*
* \param my_pipe What to close.
*
* \return Nothing
*/
static void pipe_close(int *my_pipe)
{
if (my_pipe[0] > -1) {
close(my_pipe[0]);
my_pipe[0] = -1;
}
if (my_pipe[1] > -1) {
close(my_pipe[1]);
my_pipe[1] = -1;
}
}
/*!
* \internal
* \brief Initialize a pipe as non-blocking.
* \since 12.0.0
*
* \param my_pipe What to initialize.
*
* \retval 0 on success.
* \retval -1 on error.
*/
static int pipe_init_nonblock(int *my_pipe)
{
int flags;
my_pipe[0] = -1;
my_pipe[1] = -1;
if (pipe(my_pipe)) {
ast_log(LOG_WARNING, "Can't create pipe! Try increasing max file descriptors with ulimit -n\n");
return -1;
}
flags = fcntl(my_pipe[0], F_GETFL);
if (fcntl(my_pipe[0], F_SETFL, flags | O_NONBLOCK) < 0) {
ast_log(LOG_WARNING, "Unable to set read pipe nonblocking! (%d: %s)\n",
errno, strerror(errno));
return -1;
}
flags = fcntl(my_pipe[1], F_GETFL);
if (fcntl(my_pipe[1], F_SETFL, flags | O_NONBLOCK) < 0) {
ast_log(LOG_WARNING, "Unable to set write pipe nonblocking! (%d: %s)\n",
errno, strerror(errno));
return -1;
}
return 0;
}
/* Destroy elements of the bridge channel structure and the bridge channel structure itself */
static void bridge_channel_destroy(void *obj)
{
@@ -2927,7 +2852,7 @@ static void bridge_channel_destroy(void *obj)
while ((fr = AST_LIST_REMOVE_HEAD(&bridge_channel->wr_queue, frame_list))) {
bridge_frame_free(fr);
}
pipe_close(bridge_channel->alert_pipe);
ast_alertpipe_close(bridge_channel->alert_pipe);
ast_cond_destroy(&bridge_channel->cond);
@@ -2944,7 +2869,7 @@ struct ast_bridge_channel *bridge_channel_internal_alloc(struct ast_bridge *brid
return NULL;
}
ast_cond_init(&bridge_channel->cond, NULL);
if (pipe_init_nonblock(bridge_channel->alert_pipe)) {
if (ast_alertpipe_init(bridge_channel->alert_pipe)) {
ao2_ref(bridge_channel, -1);
return NULL;
}