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Optimize latches to send fewer signals.

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Don't send signals to processes that aren't sleeping.

Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CA+hUKGJjxPDpzBE0a3hyUywBvaZuC89yx3jK9RFZgfv_KHU7gg@mail.gmail.com
This commit is contained in:
Thomas Munro 2021-03-01 11:51:15 +13:00
parent d1b90995e8
commit c8f3bc2401
2 changed files with 25 additions and 0 deletions
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24
src/backend/storage/ipc/latch.c
View File

@ -274,6 +274,7 @@ void
InitLatch(Latch *latch)
{
latch->is_set = false;
latch->maybe_sleeping = false;
latch->owner_pid = MyProcPid;
latch->is_shared = false;
@ -321,6 +322,7 @@ InitSharedLatch(Latch *latch)
#endif
latch->is_set = false;
latch->maybe_sleeping = false;
latch->owner_pid = 0;
latch->is_shared = true;
}
@ -523,6 +525,10 @@ SetLatch(Latch *latch)
latch->is_set = true;
pg_memory_barrier();
if (!latch->maybe_sleeping)
return;
#ifndef WIN32
/*
@ -589,6 +595,7 @@ ResetLatch(Latch *latch)
{
/* Only the owner should reset the latch */
Assert(latch->owner_pid == MyProcPid);
Assert(latch->maybe_sleeping == false);
latch->is_set = false;
@ -1270,6 +1277,14 @@ WaitEventSetWait(WaitEventSet *set, long timeout,
* ordering, so that we cannot miss seeing is_set if a notification
* has already been queued.
*/
if (set->latch && !set->latch->is_set)
{
/* about to sleep on a latch */
set->latch->maybe_sleeping = true;
pg_memory_barrier();
/* and recheck */
}
if (set->latch && set->latch->is_set)
{
occurred_events->fd = PGINVALID_SOCKET;
@ -1280,6 +1295,9 @@ WaitEventSetWait(WaitEventSet *set, long timeout,
occurred_events++;
returned_events++;
/* could have been set above */
set->latch->maybe_sleeping = false;
break;
}
@ -1291,6 +1309,12 @@ WaitEventSetWait(WaitEventSet *set, long timeout,
rc = WaitEventSetWaitBlock(set, cur_timeout,
occurred_events, nevents);
if (set->latch)
{
Assert(set->latch->maybe_sleeping);
set->latch->maybe_sleeping = false;
}
if (rc == -1)
break; /* timeout occurred */
else

1
src/include/storage/latch.h
View File

@ -110,6 +110,7 @@
typedef struct Latch
{
sig_atomic_t is_set;
sig_atomic_t maybe_sleeping;
bool is_shared;
int owner_pid;
#ifdef WIN32