On 2014-11-05 00:26, Peter Meerwald wrote:
From: Peter Meerwald <[email protected]>
when the wakeup pipe became ready, and poll() returned
just one descriptor, we can stop scanning io_events
Eh, does this really make things faster?
Right now it seems to add another syscall - with the patch, we call
clear_wakeup -> pa_read -> read syscall twice per iteration, once from
dispatch_pollfds and once from pa_mainloop_prepare.
In addition, I don't see anything particular time consuming in looping
through a few io_events.
Replacing the wakeup pipe with a pa_fdsem would be an interesting
optimisation though, as pa_fdsem has a few atomic operations to avoid
the entire write-poll-read cycle if no thread is currently waiting for
the fdsem.
Signed-off-by: Peter Meerwald <[email protected]>
---
src/pulse/mainloop.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/src/pulse/mainloop.c b/src/pulse/mainloop.c
index c7a5236..a7a3c48 100644
--- a/src/pulse/mainloop.c
+++ b/src/pulse/mainloop.c
@@ -635,6 +635,15 @@ static void rebuild_pollfds(pa_mainloop *m) {
m->rebuild_pollfds = false;
}
+static void clear_wakeup(pa_mainloop *m) {
+ char c[10];
+
+ pa_assert(m);
+
+ while (pa_read(m->wakeup_pipe[0], &c, sizeof(c), &m->wakeup_pipe_type) ==
sizeof(c))
+ ;
+}
+
static unsigned dispatch_pollfds(pa_mainloop *m) {
pa_io_event *e;
unsigned r = 0, k;
@@ -642,6 +651,11 @@ static unsigned dispatch_pollfds(pa_mainloop *m) {
pa_assert(m->poll_func_ret > 0);
k = m->poll_func_ret;
+ if (m->pollfds[0].revents) {
+ clear_wakeup(m);
+ m->pollfds[0].revents = 0;
+ k--;
+ }
PA_LLIST_FOREACH(e, m->io_events) {
@@ -775,20 +789,10 @@ void pa_mainloop_wakeup(pa_mainloop *m) {
pa_log("pa_write() failed while trying to wake up the mainloop: %s",
pa_cstrerror(errno));
}
-static void clear_wakeup(pa_mainloop *m) {
- char c[10];
-
- pa_assert(m);
-
- while (pa_read(m->wakeup_pipe[0], &c, sizeof(c), &m->wakeup_pipe_type) ==
sizeof(c))
- ;
-}
-
int pa_mainloop_prepare(pa_mainloop *m, int timeout) {
pa_assert(m);
pa_assert(m->state == STATE_PASSIVE);
- clear_wakeup(m);
scan_dead(m);
if (m->quit)
--
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic
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