v1-0001-Add-GUCs-to-tune-MultiXact-SLRUs.patch

From 17ba50c29aafd2de81462e0aca70c8629076e52c Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 9 May 2020 16:42:07 +0500
Subject: [PATCH v1 1/3] Add GUCs to tune MultiXact SLRUs

---
 doc/src/sgml/config.sgml               | 31 ++++++++++++++++++++++++++
 src/backend/access/transam/multixact.c |  8 +++----
 src/backend/utils/init/globals.c       |  3 +++
 src/backend/utils/misc/guc.c           | 22 ++++++++++++++++++
 src/include/access/multixact.h         |  4 ----
 src/include/miscadmin.h                |  2 ++
 6 files changed, 62 insertions(+), 8 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3aea1763b4..71aa5c4900 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1746,6 +1746,37 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+    <varlistentry id="guc-multixact-offsets-slru-buffers" xreflabel="multixact_offsets_slru_buffers">
+      <term><varname>multixact_offsets_slru_buffers</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>multixact_offsets_slru_buffers</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Specifies the amount of memory to be used for MultiXact offsets. MultiXact offsets
+        are used to store informaion about offsets of multiple row lockers (caused by SELECT FOR UPDATE and others).
+        It defaults to 64 kilobytes (<literal>64KB</literal>).
+       </para>
+      </listitem>
+     </varlistentry>
+
+    <varlistentry id="guc-multixact-members-slru-buffers" xreflabel="multixact_members_slru_buffers">
+      <term><varname>multixact_members_slru_buffers</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>multixact_members_slru_buffers</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Specifies the amount of memory to be used for MultiXact members. MultiXact members
+        are used to store informaion about XIDs of multiple row lockers. Tipically <varname>multixact_members_slru_buffers</varname>
+        is twice more than <varname>multixact_offsets_slru_buffers</varname>.
+        It defaults to 128 kilobytes (<literal>128KB</literal>).
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-max-stack-depth" xreflabel="max_stack_depth">
       <term><varname>max_stack_depth</varname> (<type>integer</type>)
       <indexterm>
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index e2aa5c9ce4..d2ac029b98 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1812,8 +1812,8 @@ MultiXactShmemSize(void)
 			 mul_size(sizeof(MultiXactId) * 2, MaxOldestSlot))
 
 	size = SHARED_MULTIXACT_STATE_SIZE;
-	size = add_size(size, SimpleLruShmemSize(NUM_MXACTOFFSET_BUFFERS, 0));
-	size = add_size(size, SimpleLruShmemSize(NUM_MXACTMEMBER_BUFFERS, 0));
+	size = add_size(size, SimpleLruShmemSize(multixact_offsets_slru_buffers, 0));
+	size = add_size(size, SimpleLruShmemSize(multixact_members_slru_buffers, 0));
 
 	return size;
 }
@@ -1829,11 +1829,11 @@ MultiXactShmemInit(void)
 	MultiXactMemberCtl->PagePrecedes = MultiXactMemberPagePrecedes;
 
 	SimpleLruInit(MultiXactOffsetCtl,
-				  "multixact_offset", NUM_MXACTOFFSET_BUFFERS, 0,
+				  "multixact_offset", multixact_offsets_slru_buffers, 0,
 				  MultiXactOffsetControlLock, "pg_multixact/offsets",
 				  LWTRANCHE_MXACTOFFSET_BUFFERS);
 	SimpleLruInit(MultiXactMemberCtl,
-				  "multixact_member", NUM_MXACTMEMBER_BUFFERS, 0,
+				  "multixact_member", multixact_members_slru_buffers, 0,
 				  MultiXactMemberControlLock, "pg_multixact/members",
 				  LWTRANCHE_MXACTMEMBER_BUFFERS);
 
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index eb19644419..aebfbdb67c 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -148,3 +148,6 @@ int			VacuumCostBalance = 0;	/* working state for vacuum */
 bool		VacuumCostActive = false;
 
 double		vacuum_cleanup_index_scale_factor;
+
+int			multixact_offsets_slru_buffers = 8;
+int			multixact_members_slru_buffers = 16;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 5bdc02fce2..b139e387f3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2270,6 +2270,28 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"multixact_offsets_slru_buffers", PGC_POSTMASTER, RESOURCES_MEM,
+			gettext_noop("Sets the number of shared memory buffers used for MultiXact offsets SLRU."),
+			NULL,
+			GUC_UNIT_BLOCKS
+		},
+		&multixact_offsets_slru_buffers,
+		8, 2, INT_MAX / 2,
+		NULL, NULL, NULL
+	},
+
+	{
+		{"multixact_members_slru_buffers", PGC_POSTMASTER, RESOURCES_MEM,
+			gettext_noop("Sets the number of shared memory buffers used for MultiXact members SLRU."),
+			NULL,
+			GUC_UNIT_BLOCKS
+		},
+		&multixact_members_slru_buffers,
+		16, 2, INT_MAX / 2,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"temp_buffers", PGC_USERSET, RESOURCES_MEM,
 			gettext_noop("Sets the maximum number of temporary buffers used by each session."),
diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h
index af4aac08bd..848398bf1e 100644
--- a/src/include/access/multixact.h
+++ b/src/include/access/multixact.h
@@ -28,10 +28,6 @@
 
 #define MaxMultiXactOffset	((MultiXactOffset) 0xFFFFFFFF)
 
-/* Number of SLRU buffers to use for multixact */
-#define NUM_MXACTOFFSET_BUFFERS		8
-#define NUM_MXACTMEMBER_BUFFERS		16
-
 /*
  * Possible multixact lock modes ("status").  The first four modes are for
  * tuple locks (FOR KEY SHARE, FOR SHARE, FOR NO KEY UPDATE, FOR UPDATE); the
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 14fa127ab1..95f4633a88 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -161,6 +161,8 @@ extern PGDLLIMPORT int MaxBackends;
 extern PGDLLIMPORT int MaxConnections;
 extern PGDLLIMPORT int max_worker_processes;
 extern PGDLLIMPORT int max_parallel_workers;
+extern PGDLLIMPORT int multixact_offsets_slru_buffers;
+extern PGDLLIMPORT int multixact_members_slru_buffers;
 
 extern PGDLLIMPORT int MyProcPid;
 extern PGDLLIMPORT pg_time_t MyStartTime;
-- 
2.24.2 (Apple Git-127)