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Commit6148656

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Use EVFILT_SIGNAL for kqueue latches.
Cut down on system calls and other overheads by waiting for SIGURGexplicitly with kqueue instead of using a signal handler and self-pipe.Affects *BSD and macOS systems.This leaves only the poll implementation with a signal handler and thetraditional self-pipe trick.Discussion:https://postgr.es/m/CA+hUKGJjxPDpzBE0a3hyUywBvaZuC89yx3jK9RFZgfv_KHU7gg@mail.gmail.com
1 parent6a2a70a commit6148656

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+38
-17
lines changed

1 file changed

+38
-17
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‎src/backend/storage/ipc/latch.c

Lines changed: 38 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,8 @@
1818
* don't need to register a signal handler or create our own self-pipe. We
1919
* assume that any system that has Linux epoll() also has Linux signalfd().
2020
*
21+
* The kqueue() implementation waits for SIGURG with EVFILT_SIGNAL.
22+
*
2123
* The Windows implementation uses Windows events that are inherited by all
2224
* postmaster child processes. There's no need for the self-pipe trick there.
2325
*
@@ -150,7 +152,7 @@ static volatile sig_atomic_t waiting = false;
150152
staticintsignal_fd=-1;
151153
#endif
152154

153-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
155+
#if defined(WAIT_USE_POLL)
154156
/* Read and write ends of the self-pipe */
155157
staticintselfpipe_readfd=-1;
156158
staticintselfpipe_writefd=-1;
@@ -189,7 +191,7 @@ static inline int WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
189191
void
190192
InitializeLatchSupport(void)
191193
{
192-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
194+
#if defined(WAIT_USE_POLL)
193195
intpipefd[2];
194196

195197
if (IsUnderPostmaster)
@@ -277,6 +279,11 @@ InitializeLatchSupport(void)
277279
elog(FATAL,"signalfd() failed");
278280
ReserveExternalFD();
279281
#endif
282+
283+
#ifdefWAIT_USE_KQUEUE
284+
/* Ignore SIGURG, because we'll receive it via kqueue. */
285+
pqsignal(SIGURG,SIG_IGN);
286+
#endif
280287
}
281288

282289
void
@@ -300,7 +307,7 @@ InitializeLatchWaitSet(void)
300307
void
301308
ShutdownLatchSupport(void)
302309
{
303-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
310+
#if defined(WAIT_USE_POLL)
304311
pqsignal(SIGURG,SIG_IGN);
305312
#endif
306313

@@ -310,7 +317,7 @@ ShutdownLatchSupport(void)
310317
LatchWaitSet=NULL;
311318
}
312319

313-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
320+
#if defined(WAIT_USE_POLL)
314321
close(selfpipe_readfd);
315322
close(selfpipe_writefd);
316323
selfpipe_readfd=-1;
@@ -335,7 +342,7 @@ InitLatch(Latch *latch)
335342
latch->owner_pid=MyProcPid;
336343
latch->is_shared= false;
337344

338-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
345+
#if defined(WAIT_USE_POLL)
339346
/* Assert InitializeLatchSupport has been called in this process */
340347
Assert(selfpipe_readfd >=0&&selfpipe_owner_pid==MyProcPid);
341348
#elif defined(WAIT_USE_WIN32)
@@ -399,7 +406,7 @@ OwnLatch(Latch *latch)
399406
/* Sanity checks */
400407
Assert(latch->is_shared);
401408

402-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
409+
#if defined(WAIT_USE_POLL)
403410
/* Assert InitializeLatchSupport has been called in this process */
404411
Assert(selfpipe_readfd >=0&&selfpipe_owner_pid==MyProcPid);
405412
#endif
@@ -611,7 +618,7 @@ SetLatch(Latch *latch)
611618
return;
612619
elseif (owner_pid==MyProcPid)
613620
{
614-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
621+
#if defined(WAIT_USE_POLL)
615622
if (waiting)
616623
sendSelfPipeByte();
617624
#else
@@ -898,13 +905,15 @@ AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch,
898905
{
899906
set->latch=latch;
900907
set->latch_pos=event->pos;
901-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
908+
#if defined(WAIT_USE_POLL)
902909
event->fd=selfpipe_readfd;
903910
#elif defined(WAIT_USE_EPOLL)
904911
event->fd=signal_fd;
905912
#else
906913
event->fd=PGINVALID_SOCKET;
914+
#ifdefWAIT_USE_EPOLL
907915
returnevent->pos;
916+
#endif
908917
#endif
909918
}
910919
elseif (events==WL_POSTMASTER_DEATH)
@@ -1125,6 +1134,18 @@ WaitEventAdjustKqueueAddPostmaster(struct kevent *k_ev, WaitEvent *event)
11251134
AccessWaitEvent(k_ev)=event;
11261135
}
11271136

1137+
staticinlinevoid
1138+
WaitEventAdjustKqueueAddLatch(structkevent*k_ev,WaitEvent*event)
1139+
{
1140+
/* For now latch can only be added, not removed. */
1141+
k_ev->ident=SIGURG;
1142+
k_ev->filter=EVFILT_SIGNAL;
1143+
k_ev->flags=EV_ADD;
1144+
k_ev->fflags=0;
1145+
k_ev->data=0;
1146+
AccessWaitEvent(k_ev)=event;
1147+
}
1148+
11281149
/*
11291150
* old_events is the previous event mask, used to compute what has changed.
11301151
*/
@@ -1156,18 +1177,21 @@ WaitEventAdjustKqueue(WaitEventSet *set, WaitEvent *event, int old_events)
11561177
*/
11571178
WaitEventAdjustKqueueAddPostmaster(&k_ev[count++],event);
11581179
}
1180+
elseif (event->events==WL_LATCH_SET)
1181+
{
1182+
/* We detect latch wakeup using a signal event. */
1183+
WaitEventAdjustKqueueAddLatch(&k_ev[count++],event);
1184+
}
11591185
else
11601186
{
11611187
/*
11621188
* We need to compute the adds and deletes required to get from the
11631189
* old event mask to the new event mask, since kevent treats readable
11641190
* and writable as separate events.
11651191
*/
1166-
if (old_events==WL_LATCH_SET||
1167-
(old_events&WL_SOCKET_READABLE))
1192+
if (old_events&WL_SOCKET_READABLE)
11681193
old_filt_read= true;
1169-
if (event->events==WL_LATCH_SET||
1170-
(event->events&WL_SOCKET_READABLE))
1194+
if (event->events&WL_SOCKET_READABLE)
11711195
new_filt_read= true;
11721196
if (old_events&WL_SOCKET_WRITEABLE)
11731197
old_filt_write= true;
@@ -1620,11 +1644,8 @@ WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
16201644
occurred_events->events=0;
16211645

16221646
if (cur_event->events==WL_LATCH_SET&&
1623-
cur_kqueue_event->filter==EVFILT_READ)
1647+
cur_kqueue_event->filter==EVFILT_SIGNAL)
16241648
{
1625-
/* There's data in the self-pipe, clear it. */
1626-
drain();
1627-
16281649
if (set->latch&&set->latch->is_set)
16291650
{
16301651
occurred_events->fd=PGINVALID_SOCKET;
@@ -1999,7 +2020,7 @@ WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
19992020
}
20002021
#endif
20012022

2002-
#if defined(WAIT_USE_POLL)|| defined(WAIT_USE_KQUEUE)
2023+
#if defined(WAIT_USE_POLL)
20032024

20042025
/*
20052026
* SetLatch uses SIGURG to wake up the process waiting on the latch.

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