From: Andres Freund <andres@anarazel.de>
Date: Sat, 31 Oct 2020 00:12:09 +0000 (-0700)
Subject: latch / signal perf stuff: generic
X-Git-Url: http://git.postgresql.org/gitweb/review?a=commitdiff_plain;h=8e645b68febc18bb984176c69bbc6247e21a8059;p=users%2Fandresfreund%2Fpostgres.git

latch / signal perf stuff: generic

Author:
Reviewed-By:
Discussion: https://postgr.es/m/
Backpatch:
---

diff --git a/src/backend/libpq/pqsignal.c b/src/backend/libpq/pqsignal.c
index b43af22030..8d97b008ab 100644
--- a/src/backend/libpq/pqsignal.c
+++ b/src/backend/libpq/pqsignal.c
@@ -19,7 +19,8 @@
 
 
 /* Global variables */
-sigset_t	UnBlockSig,
+sigset_t	SleepSig,
+			UnBlockSig,
 			BlockSig,
 			StartupBlockSig;
 
@@ -40,6 +41,7 @@ sigset_t	UnBlockSig,
 void
 pqinitmask(void)
 {
+	sigemptyset(&SleepSig);
 	sigemptyset(&UnBlockSig);
 
 	/* First set all signals, then clear some. */
@@ -94,6 +96,8 @@ pqinitmask(void)
 #ifdef SIGALRM
 	sigdelset(&StartupBlockSig, SIGALRM);
 #endif
+
+	sigaddset(&UnBlockSig, SIGURG);
 }
 
 /*
diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 47e60ca561..211859f77d 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -464,7 +464,9 @@ AutoVacLauncherMain(int argc, char *argv[])
 
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
+	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, avl_sigusr2_handler);
+	pqsignal(SIGURG, latch_sigurg_handler);
 	pqsignal(SIGFPE, FloatExceptionHandler);
 	pqsignal(SIGCHLD, SIG_DFL);
 
@@ -1543,6 +1545,7 @@ AutoVacWorkerMain(int argc, char *argv[])
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
+	pqsignal(SIGURG, latch_sigurg_handler);
 	pqsignal(SIGFPE, FloatExceptionHandler);
 	pqsignal(SIGCHLD, SIG_DFL);
 
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index dd3dad3de3..c0282e882c 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -330,6 +330,7 @@ BackgroundWorkerStateChange(bool allow_new_workers)
 			pg_memory_barrier();
 			slot->pid = 0;
 			slot->in_use = false;
+			/* FIXME: shouldn't this use SetLatch() or something */
 			if (notify_pid != 0)
 				kill(notify_pid, SIGUSR1);
 
@@ -779,6 +780,7 @@ StartBackgroundWorker(void)
 		 */
 		pqsignal(SIGINT, StatementCancelHandler);
 		pqsignal(SIGUSR1, procsignal_sigusr1_handler);
+		pqsignal(SIGURG, latch_sigurg_handler);
 		pqsignal(SIGFPE, FloatExceptionHandler);
 
 		/* XXX Any other handlers needed here? */
@@ -787,6 +789,7 @@ StartBackgroundWorker(void)
 	{
 		pqsignal(SIGINT, SIG_IGN);
 		pqsignal(SIGUSR1, bgworker_sigusr1_handler);
+		pqsignal(SIGURG, latch_sigurg_handler);
 		pqsignal(SIGFPE, SIG_IGN);
 	}
 	pqsignal(SIGTERM, bgworker_die);
diff --git a/src/backend/postmaster/bgwriter.c b/src/backend/postmaster/bgwriter.c
index 715d5195bb..66864a42df 100644
--- a/src/backend/postmaster/bgwriter.c
+++ b/src/backend/postmaster/bgwriter.c
@@ -109,6 +109,7 @@ BackgroundWriterMain(void)
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
+	pqsignal(SIGURG, latch_sigurg_handler);
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 524fc4f112..e208b5878d 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -203,6 +203,7 @@ CheckpointerMain(void)
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SignalHandlerForShutdownRequest);
+	pqsignal(SIGURG, latch_sigurg_handler);
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
diff --git a/src/backend/postmaster/startup.c b/src/backend/postmaster/startup.c
index f781fdc6fc..1fce630b47 100644
--- a/src/backend/postmaster/startup.c
+++ b/src/backend/postmaster/startup.c
@@ -180,6 +180,7 @@ StartupProcessMain(void)
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, StartupProcTriggerHandler);
+	pqsignal(SIGURG, latch_sigurg_handler);
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 5f36796fcd..92ed7519a2 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -107,6 +107,7 @@ WalWriterMain(void)
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN); /* not used */
+	pqsignal(SIGURG, latch_sigurg_handler);
 
 	/*
 	 * Reset some signals that are accepted by postmaster but not here
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index 723f513d8b..751c2d38cf 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -264,6 +264,7 @@ WalReceiverMain(void)
 	pqsignal(SIGPIPE, SIG_IGN);
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, SIG_IGN);
+	pqsignal(SIGURG, latch_sigurg_handler);
 
 	/* Reset some signals that are accepted by postmaster but not here */
 	pqsignal(SIGCHLD, SIG_DFL);
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index fe0d368a35..dfdea4f4c4 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -3054,6 +3054,7 @@ WalSndSignals(void)
 	pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 	pqsignal(SIGUSR2, WalSndLastCycleHandler);	/* request a last cycle and
 												 * shutdown */
+	pqsignal(SIGURG, latch_sigurg_handler);
 
 	/* Reset some signals that are accepted by postmaster but not here */
 	pqsignal(SIGCHLD, SIG_DFL);
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
index f2d005eea0..1d9a375078 100644
--- a/src/backend/storage/ipc/latch.c
+++ b/src/backend/storage/ipc/latch.c
@@ -46,6 +46,7 @@
 #include <poll.h>
 #endif
 
+#include "libpq/pqsignal.h"
 #include "miscadmin.h"
 #include "pgstat.h"
 #include "port/atomics.h"
@@ -274,6 +275,7 @@ void
 InitLatch(Latch *latch)
 {
 	latch->is_set = false;
+	latch->maybe_sleeping = false;
 	latch->owner_pid = MyProcPid;
 	latch->is_shared = false;
 
@@ -321,6 +323,7 @@ InitSharedLatch(Latch *latch)
 #endif
 
 	latch->is_set = false;
+	latch->maybe_sleeping = false;
 	latch->owner_pid = 0;
 	latch->is_shared = true;
 }
@@ -523,6 +526,11 @@ SetLatch(Latch *latch)
 
 	latch->is_set = true;
 
+    pg_memory_barrier();
+
+	if (!latch->maybe_sleeping)
+		return;
+
 #ifndef WIN32
 
 	/*
@@ -556,7 +564,7 @@ SetLatch(Latch *latch)
 			sendSelfPipeByte();
 	}
 	else
-		kill(owner_pid, SIGUSR1);
+		kill(owner_pid, SIGURG);
 #else
 
 	/*
@@ -589,6 +597,7 @@ ResetLatch(Latch *latch)
 {
 	/* Only the owner should reset the latch */
 	Assert(latch->owner_pid == MyProcPid);
+	Assert(latch->maybe_sleeping == false);
 
 	latch->is_set = false;
 
@@ -1289,6 +1298,14 @@ 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;
@@ -1299,6 +1316,9 @@ WaitEventSetWait(WaitEventSet *set, long timeout,
 			occurred_events++;
 			returned_events++;
 
+			/* could have been set above */
+			set->latch->maybe_sleeping = false;
+
 			break;
 		}
 
@@ -1310,6 +1330,12 @@ 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
@@ -1355,8 +1381,8 @@ WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
 	struct epoll_event *cur_epoll_event;
 
 	/* Sleep */
-	rc = epoll_wait(set->epoll_fd, set->epoll_ret_events,
-					nevents, cur_timeout);
+	rc = epoll_pwait(set->epoll_fd, set->epoll_ret_events,
+					 nevents, cur_timeout, &SleepSig);
 
 	/* Check return code */
 	if (rc < 0)
@@ -1399,6 +1425,8 @@ WaitEventSetWaitBlock(WaitEventSet *set, int cur_timeout,
 		if (cur_event->events == WL_LATCH_SET &&
 			cur_epoll_event->events & (EPOLLIN | EPOLLERR | EPOLLHUP))
 		{
+			Assert(set->latch);
+
 			/* There's data in the self-pipe, clear it. */
 			drainSelfPipe();
 
@@ -1946,6 +1974,14 @@ latch_sigusr1_handler(void)
 	if (waiting)
 		sendSelfPipeByte();
 }
+
+void
+latch_sigurg_handler(SIGNAL_ARGS)
+{
+	if (waiting)
+		sendSelfPipeByte();
+}
+
 #endif							/* !WIN32 */
 
 /* Send one byte to the self-pipe, to wake up WaitLatch */
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index 583efaecff..876abf1b51 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -587,7 +587,7 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 
 	SetLatch(MyLatch);
 
-	latch_sigusr1_handler();
+	//latch_sigusr1_handler();
 
 	errno = save_errno;
 }
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 28055680aa..fdb9eab73a 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3924,6 +3924,7 @@ PostgresMain(int argc, char *argv[],
 		pqsignal(SIGPIPE, SIG_IGN);
 		pqsignal(SIGUSR1, procsignal_sigusr1_handler);
 		pqsignal(SIGUSR2, SIG_IGN);
+		pqsignal(SIGURG, latch_sigurg_handler);
 		pqsignal(SIGFPE, FloatExceptionHandler);
 
 		/*
diff --git a/src/include/libpq/pqsignal.h b/src/include/libpq/pqsignal.h
index 1161b13874..ee41e9732c 100644
--- a/src/include/libpq/pqsignal.h
+++ b/src/include/libpq/pqsignal.h
@@ -30,7 +30,8 @@ extern int	pqsigsetmask(int mask);
 #define sigdelset(set, signum)	(*(set) &= ~(sigmask(signum)))
 #endif							/* WIN32 */
 
-extern sigset_t UnBlockSig,
+extern sigset_t SleepSig,
+			UnBlockSig,
 			BlockSig,
 			StartupBlockSig;
 
diff --git a/src/include/storage/latch.h b/src/include/storage/latch.h
index 1468f30a8e..f13e399c08 100644
--- a/src/include/storage/latch.h
+++ b/src/include/storage/latch.h
@@ -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
@@ -184,8 +185,10 @@ extern void InitializeLatchWaitSet(void);
  */
 #ifndef WIN32
 extern void latch_sigusr1_handler(void);
+extern void latch_sigurg_handler(SIGNAL_ARGS);
 #else
 #define latch_sigusr1_handler()  ((void) 0)
+static inline void latch_sigurg_handler(SIGNAL_ARGS) {}
 #endif
 
 #endif							/* LATCH_H */