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| author | Garrett D'Amore <garrett@damore.org> | 2017-08-10 00:10:50 -0700 |
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| committer | Garrett D'Amore <garrett@damore.org> | 2017-08-10 00:10:50 -0700 |
| commit | ac5f0ef7cf501693a9db2fcbd95b7cde419cbb2a (patch) | |
| tree | 49f479185a08e8f4b2538b3fb69ab57319a4ba60 /src/core/thread.h | |
| parent | 9feb54e9c7ab116ba566086a76604338f86e3bc3 (diff) | |
| download | nng-ac5f0ef7cf501693a9db2fcbd95b7cde419cbb2a.tar.gz nng-ac5f0ef7cf501693a9db2fcbd95b7cde419cbb2a.tar.bz2 nng-ac5f0ef7cf501693a9db2fcbd95b7cde419cbb2a.zip | |
Thundering herd kills performance.
A little benchmarking showed that we were encountering far too many
wakeups, leading to severe performance degradation; we had a bunch
of threads all sleeping on the same condition variable (taskqs)
and this woke them all up, resulting in heavy mutex contention.
Since we only need one of the threads to wake, and we don't care which
one, let's just wake only one. This reduced RTT latency from about
240 us down to about 30 s. (1/8 of the former cost.)
There's still a bunch of tuning to do; performance remains worse than
we would like.
Diffstat (limited to 'src/core/thread.h')
| -rw-r--r-- | src/core/thread.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/src/core/thread.h b/src/core/thread.h index b528af2c..94b2a984 100644 --- a/src/core/thread.h +++ b/src/core/thread.h @@ -52,6 +52,9 @@ extern void nni_cv_fini(nni_cv *cv); // nni_cv_wake wakes all waiters on the condition variable. extern void nni_cv_wake(nni_cv *cv); +// nni_cv_wake wakes just one waiter on the condition variable. +extern void nni_cv_wake1(nni_cv *cv); + // nni_cv_wait waits until nni_cv_wake is called on the condition variable. // The wait is indefinite. Premature wakeups are possible, so the caller // must verify any related condition. |