Date: Sat, 10 Jul 2021 00:58:04 GMT From: Alexander Motin <mav@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 63ca9ea4f34d - main - Use sleepq_signal(SLEEPQ_DROP) in cv_signal(). Message-ID: <202107100058.16A0w42M085354@gitrepo.freebsd.org>
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The branch main has been updated by mav: URL: https://cgit.FreeBSD.org/src/commit/?id=63ca9ea4f34d887b66c7b9f1710f5e4be543ebed commit 63ca9ea4f34d887b66c7b9f1710f5e4be543ebed Author: Alexander Motin <mav@FreeBSD.org> AuthorDate: 2021-07-10 00:52:40 +0000 Commit: Alexander Motin <mav@FreeBSD.org> CommitDate: 2021-07-10 00:57:58 +0000 Use sleepq_signal(SLEEPQ_DROP) in cv_signal(). Same as wakeup_one()/wakeup_any() commit before it reduces the lock hold time and so contention. MFC after: 1 week --- sys/kern/kern_condvar.c | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-) diff --git a/sys/kern/kern_condvar.c b/sys/kern/kern_condvar.c index e26b689b4e11..ffceee44a5c0 100644 --- a/sys/kern/kern_condvar.c +++ b/sys/kern/kern_condvar.c @@ -397,26 +397,23 @@ _cv_timedwait_sig_sbt(struct cv *cvp, struct lock_object *lock, void cv_signal(struct cv *cvp) { - int wakeup_swapper; if (cvp->cv_waiters == 0) return; - wakeup_swapper = 0; sleepq_lock(cvp); - if (cvp->cv_waiters > 0) { - if (cvp->cv_waiters == CV_WAITERS_BOUND && - sleepq_lookup(cvp) == NULL) { - cvp->cv_waiters = 0; - } else { - if (cvp->cv_waiters < CV_WAITERS_BOUND) - cvp->cv_waiters--; - wakeup_swapper = sleepq_signal(cvp, SLEEPQ_CONDVAR, 0, - 0); - } + if (cvp->cv_waiters == 0) { + sleepq_release(cvp); + return; + } + if (cvp->cv_waiters == CV_WAITERS_BOUND && sleepq_lookup(cvp) == NULL) { + cvp->cv_waiters = 0; + sleepq_release(cvp); + } else { + if (cvp->cv_waiters < CV_WAITERS_BOUND) + cvp->cv_waiters--; + if (sleepq_signal(cvp, SLEEPQ_CONDVAR | SLEEPQ_DROP, 0, 0)) + kick_proc0(); } - sleepq_release(cvp); - if (wakeup_swapper) - kick_proc0(); } /*
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