v6-0004-Add-GUCs-to-tune-MultiXact-SLRUs.patch

From a5e15ae42bd6c99d39bac7a9988f586c48ceba13 Mon Sep 17 00:00:00 2001
From: Andrey Borodin <amborodin@acm.org>
Date: Sat, 9 May 2020 16:42:07 +0500
Subject: [PATCH v6 4/4] 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       |  2 ++
 src/backend/utils/misc/guc.c           | 22 ++++++++++++++++++
 src/include/access/multixact.h         |  4 ----
 src/include/miscadmin.h                |  2 ++
 6 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index fd4ca29347..d2ca4934de 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1838,6 +1838,37 @@ include_dir 'conf.d'
        </para>
       </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>)
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 70d977cba3..1c177242c5 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1866,8 +1866,8 @@ MultiXactShmemSize(void)
 			 mul_size(sizeof(MultiXactId) * 2, MaxOldestSlot))
 
 	size = SHARED_MULTIXACT_STATE_SIZE;
-	size = add_size(size, SimpleLruShmemSize(NUM_MULTIXACTOFFSET_BUFFERS, 0));
-	size = add_size(size, SimpleLruShmemSize(NUM_MULTIXACTMEMBER_BUFFERS, 0));
+	size = add_size(size, SimpleLruShmemSize(multixact_offsets_slru_buffers, 0));
+	size = add_size(size, SimpleLruShmemSize(multixact_members_slru_buffers, 0));
 
 	return size;
 }
@@ -1883,12 +1883,12 @@ MultiXactShmemInit(void)
 	MultiXactMemberCtl->PagePrecedes = MultiXactMemberPagePrecedes;
 
 	SimpleLruInit(MultiXactOffsetCtl,
-				  "MultiXactOffset", NUM_MULTIXACTOFFSET_BUFFERS, 0,
+				  "MultiXactOffset", multixact_offsets_slru_buffers, 0,
 				  MultiXactOffsetSLRULock, "pg_multixact/offsets",
 				  LWTRANCHE_MULTIXACTOFFSET_BUFFER,
 				  SYNC_HANDLER_MULTIXACT_OFFSET);
 	SimpleLruInit(MultiXactMemberCtl,
-				  "MultiXactMember", NUM_MULTIXACTMEMBER_BUFFERS, 0,
+				  "MultiXactMember", multixact_members_slru_buffers, 0,
 				  MultiXactMemberSLRULock, "pg_multixact/members",
 				  LWTRANCHE_MULTIXACTMEMBER_BUFFER,
 				  SYNC_HANDLER_MULTIXACT_MEMBER);
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index 9ca71933dc..a5ec7bfe88 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -151,3 +151,5 @@ bool		VacuumCostActive = false;
 double		vacuum_cleanup_index_scale_factor;
 
 int         multixact_local_cache_entries = 256;
+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 d667578cc3..7682c8be1e 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2267,6 +2267,28 @@ 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 9a30380901..630ceaea4d 100644
--- a/src/include/access/multixact.h
+++ b/src/include/access/multixact.h
@@ -29,10 +29,6 @@
 
 #define MaxMultiXactOffset	((MultiXactOffset) 0xFFFFFFFF)
 
-/* Number of SLRU buffers to use for multixact */
-#define NUM_MULTIXACTOFFSET_BUFFERS		8
-#define NUM_MULTIXACTMEMBER_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 01af61c963..ef8abea84d 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 multixact_local_cache_entries;
 
-- 
2.24.3 (Apple Git-128)