Mar 31, 2022 · Mar 25, 2022
diff --git a/pg_wait_sampling.c b/pg_wait_sampling.c
 #include "miscadmin.h"
 #include "optimizer/planner.h"
 #include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #if PG_VERSION_NUM >= 120000
 #include "replication/walsender.h"
 #endif
 #include "storage/ipc.h"
 #include "storage/pg_shmem.h"
 #include "storage/procarray.h"

 /*
 * Calculate max processes count.
 * Look at InitProcGlobal (proc.c) and TotalProcs variable in it
 * if something wrong here.
 *
 * The value has to be in sync with ProcGlobal->allProcCount, initialized in
 * InitProcGlobal() (proc.c).
 *
 * We calculate the value here as it won't initialized when we need need
 * it during _PG_init().
 *
 * Note that the value returned during _PG_init() might be different from the
 * value returned later if some third-party modules change one of the
 * underlying GUC.  This isn't ideal but can't lead to a crash, as the value
 * returned during _PG_init() is only used to ask for additional shmem with
 * RequestAddinShmemSpace(), and postgres has an extra 100kB of shmem to
 * compensate some small unaccounted usage.  So if the value later changes, we
 * will allocate and initialize the new (and correct) memory size, which
 * will either work thanks for the extra 100kB of shmem, of fail (and prevent
 * postgres startup) due to an out of shared memory error.
 */
 static int
 get_max_procs_count(void)
 {
 int count = 0;

 /* MyProcs, including autovacuum workers and launcher */
 count += MaxBackends;
 /*
 * MaxBackends: bgworkers, autovacuum workers and launcher.
 * This has to be in sync with the value computed in
 * InitializeMaxBackends() (postinit.c)
 */
 count += MaxConnections + autovacuum_max_workers + 1
 + max_worker_processes;

 /*
 * Starting with pg12, wal senders aren't part of MaxConnections anymore
 * and have to be accounted for.
 */
 #if PG_VERSION_NUM >= 120000
 count += max_wal_senders;
 #endif

 /* AuxiliaryProcs */
 count += NUM_AUXILIARY_PROCS;
 /* Prepared xacts */
 count += max_prepared_xacts;

 return count;
 }
Original file line number	Diff line number	Diff line change
Expand Up		@@ -17,6 +17,10 @@
		#include "miscadmin.h"
		#include "optimizer/planner.h"
		#include "pgstat.h"
		#include "postmaster/autovacuum.h"
		#if PG_VERSION_NUM >= 120000
		#include "replication/walsender.h"
		#endif
		#include "storage/ipc.h"
		#include "storage/pg_shmem.h"
		#include "storage/procarray.h"
Expand DownExpand Up		@@ -66,20 +70,46 @@ static void pgws_ExecutorEnd(QueryDesc *queryDesc);

		/*
		* Calculate max processes count.
		* Look at InitProcGlobal (proc.c) and TotalProcs variable in it
		* if something wrong here.
		*
		* The value has to be in sync with ProcGlobal->allProcCount, initialized in
		* InitProcGlobal() (proc.c).
		*
		* We calculate the value here as it won't initialized when we need need
		* it during _PG_init().
		*
		* Note that the value returned during _PG_init() might be different from the
		* value returned later if some third-party modules change one of the
		* underlying GUC. This isn't ideal but can't lead to a crash, as the value
		* returned during _PG_init() is only used to ask for additional shmem with
		* RequestAddinShmemSpace(), and postgres has an extra 100kB of shmem to
		* compensate some small unaccounted usage. So if the value later changes, we
		* will allocate and initialize the new (and correct) memory size, which
		* will either work thanks for the extra 100kB of shmem, of fail (and prevent
		* postgres startup) due to an out of shared memory error.
		*/
		static int
		get_max_procs_count(void)
		{
		int count = 0;

		/* MyProcs, including autovacuum workers and launcher */
		count += MaxBackends;
		/*
		* MaxBackends: bgworkers, autovacuum workers and launcher.
		* This has to be in sync with the value computed in
		* InitializeMaxBackends() (postinit.c)
		*/
		count += MaxConnections + autovacuum_max_workers + 1
		+ max_worker_processes;

		/*
		* Starting with pg12, wal senders aren't part of MaxConnections anymore
		* and have to be accounted for.
		*/
		#if PG_VERSION_NUM >= 120000
		count += max_wal_senders;
		#endif

		/* AuxiliaryProcs */
		count += NUM_AUXILIARY_PROCS;
		/* Prepared xacts */
		count += max_prepared_xacts;

		return count;
		}
Expand Down