From 76026728c2ba2fff65e2bdad4ebd97e674afc594 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Mon, 13 Jul 2020 13:44:36 +1200 Subject: [PATCH v5 2/7] Use WaitLatch() for condition variables. Previously, condition_variable.c created its own long lived WaitEventSet to avoid extra system calls. WaitLatch() now does that, so there is no point in wasting an extra kernel descriptor. Reviewed-by: Kyotaro Horiguchi Discussion: https://postgr.es/m/CA%2BhUKGJAC4Oqao%3DqforhNey20J8CiG2R%3DoBPqvfR0vOJrFysGw%40mail.gmail.com --- src/backend/storage/lmgr/condition_variable.c | 28 ++++--------------- 1 file changed, 5 insertions(+), 23 deletions(-) diff --git a/src/backend/storage/lmgr/condition_variable.c b/src/backend/storage/lmgr/condition_variable.c index 37b6a4eecd..2ec00397b4 100644 --- a/src/backend/storage/lmgr/condition_variable.c +++ b/src/backend/storage/lmgr/condition_variable.c @@ -30,9 +30,6 @@ /* Initially, we are not prepared to sleep on any condition variable. */ static ConditionVariable *cv_sleep_target = NULL; -/* Reusable WaitEventSet. */ -static WaitEventSet *cv_wait_event_set = NULL; - /* * Initialize a condition variable. */ @@ -62,23 +59,6 @@ ConditionVariablePrepareToSleep(ConditionVariable *cv) { int pgprocno = MyProc->pgprocno; - /* - * If first time through in this process, create a WaitEventSet, which - * we'll reuse for all condition variable sleeps. - */ - if (cv_wait_event_set == NULL) - { - WaitEventSet *new_event_set; - - new_event_set = CreateWaitEventSet(TopMemoryContext, 2); - AddWaitEventToSet(new_event_set, WL_LATCH_SET, PGINVALID_SOCKET, - MyLatch, NULL); - AddWaitEventToSet(new_event_set, WL_EXIT_ON_PM_DEATH, PGINVALID_SOCKET, - NULL, NULL); - /* Don't set cv_wait_event_set until we have a correct WES. */ - cv_wait_event_set = new_event_set; - } - /* * If some other sleep is already prepared, cancel it; this is necessary * because we have just one static variable tracking the prepared sleep, @@ -135,6 +115,7 @@ ConditionVariableTimedSleep(ConditionVariable *cv, long timeout, long cur_timeout = -1; instr_time start_time; instr_time cur_time; + int wait_events; /* * If the caller didn't prepare to sleep explicitly, then do so now and @@ -166,19 +147,20 @@ ConditionVariableTimedSleep(ConditionVariable *cv, long timeout, INSTR_TIME_SET_CURRENT(start_time); Assert(timeout >= 0 && timeout <= INT_MAX); cur_timeout = timeout; + wait_events = WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH; } + else + wait_events = WL_LATCH_SET | WL_EXIT_ON_PM_DEATH; while (true) { - WaitEvent event; bool done = false; /* * Wait for latch to be set. (If we're awakened for some other * reason, the code below will cope anyway.) */ - (void) WaitEventSetWait(cv_wait_event_set, cur_timeout, &event, 1, - wait_event_info); + (void) WaitLatch(MyLatch, wait_events, cur_timeout, wait_event_info); /* Reset latch before examining the state of the wait list. */ ResetLatch(MyLatch); -- 2.20.1