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-rw-r--r--doc/src/sgml/config.sgml21
-rw-r--r--doc/src/sgml/ref/postgres-ref.sgml3
-rw-r--r--doc/src/sgml/runtime.sgml27
-rw-r--r--src/backend/port/sysv_shmem.c43
-rw-r--r--src/backend/port/win32_shmem.c14
-rw-r--r--src/backend/storage/ipc/ipci.c14
-rw-r--r--src/backend/utils/misc/guc.c12
-rw-r--r--src/include/storage/pg_shmem.h1
8 files changed, 106 insertions, 29 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index ef0e2a77462..0a8e35c59f4 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -10289,6 +10289,27 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
</listitem>
</varlistentry>
+ <varlistentry id="guc-shared-memory-size-in-huge-pages" xreflabel="shared_memory_size_in_huge_pages">
+ <term><varname>shared_memory_size_in_huge_pages</varname> (<type>integer</type>)
+ <indexterm>
+ <primary><varname>shared_memory_size_in_huge_pages</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Reports the number of huge pages that are needed for the main shared
+ memory area based on the specified <xref linkend="guc-huge-page-size"/>.
+ If huge pages are not supported, this will be <literal>-1</literal>.
+ </para>
+ <para>
+ This setting is supported only on <productname>Linux</productname>. It
+ is always set to <literal>-1</literal> on other platforms. For more
+ details about using huge pages on <productname>Linux</productname>, see
+ <xref linkend="linux-huge-pages"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-ssl-library" xreflabel="ssl_library">
<term><varname>ssl_library</varname> (<type>string</type>)
<indexterm>
diff --git a/doc/src/sgml/ref/postgres-ref.sgml b/doc/src/sgml/ref/postgres-ref.sgml
index f72c3b04e42..55a3f6c69d1 100644
--- a/doc/src/sgml/ref/postgres-ref.sgml
+++ b/doc/src/sgml/ref/postgres-ref.sgml
@@ -143,7 +143,8 @@ PostgreSQL documentation
<para>
This can be used on a running server for most parameters. However,
the server must be shut down for some runtime-computed parameters
- (e.g., <xref linkend="guc-shared-memory-size"/> and
+ (e.g., <xref linkend="guc-shared-memory-size"/>,
+ <xref linkend="guc-shared-memory-size-in-huge-pages"/>, and
<xref linkend="guc-wal-segment-size"/>).
</para>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index f1cbc1d9e92..d74d1ed7afa 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -1442,17 +1442,14 @@ export PG_OOM_ADJUST_VALUE=0
with <varname>CONFIG_HUGETLBFS=y</varname> and
<varname>CONFIG_HUGETLB_PAGE=y</varname>. You will also have to configure
the operating system to provide enough huge pages of the desired size.
- To estimate the number of huge pages needed, start
- <productname>PostgreSQL</productname> without huge pages enabled and check
- the postmaster's anonymous shared memory segment size, as well as the
- system's default and supported huge page sizes, using the
- <filename>/proc</filename> and <filename>/sys</filename> file systems.
+ To determine the number of huge pages needed, use the
+ <command>postgres</command> command to see the value of
+ <xref linkend="guc-shared-memory-size-in-huge-pages"/>. Note that the
+ server must be shut down to view this runtime-computed parameter.
This might look like:
<programlisting>
-$ <userinput>head -1 $PGDATA/postmaster.pid</userinput>
-4170
-$ <userinput>pmap 4170 | awk '/rw-s/ &amp;&amp; /zero/ {print $2}'</userinput>
-6490428K
+$ <userinput>postgres -D $PGDATA -C shared_memory_size_in_huge_pages</userinput>
+3170
$ <userinput>grep ^Hugepagesize /proc/meminfo</userinput>
Hugepagesize: 2048 kB
$ <userinput>ls /sys/kernel/mm/hugepages</userinput>
@@ -1460,13 +1457,13 @@ hugepages-1048576kB hugepages-2048kB
</programlisting>
In this example the default is 2MB, but you can also explicitly request
- either 2MB or 1GB with <xref linkend="guc-huge-page-size"/>.
+ either 2MB or 1GB with <xref linkend="guc-huge-page-size"/> to adapt
+ the number of pages calculated by
+ <varname>shared_memory_size_in_huge_pages</varname>.
- Assuming <literal>2MB</literal> huge pages,
- <literal>6490428</literal> / <literal>2048</literal> gives approximately
- <literal>3169.154</literal>, so in this example we need at
- least <literal>3170</literal> huge pages. A larger setting would be
- appropriate if other programs on the machine also need huge pages.
+ While we need at least <literal>3170</literal> huge pages in this example,
+ a larger setting would be appropriate if other programs on the machine
+ also need huge pages.
We can set this with:
<programlisting>
# <userinput>sysctl -w vm.nr_hugepages=3170</userinput>
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c
index 9de96edf6ad..cd385c4df65 100644
--- a/src/backend/port/sysv_shmem.c
+++ b/src/backend/port/sysv_shmem.c
@@ -456,8 +456,6 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
return shmStat.shm_nattch == 0 ? SHMSTATE_UNATTACHED : SHMSTATE_ATTACHED;
}
-#ifdef MAP_HUGETLB
-
/*
* Identify the huge page size to use, and compute the related mmap flags.
*
@@ -475,13 +473,19 @@ PGSharedMemoryAttach(IpcMemoryId shmId,
* hugepage sizes, we might want to think about more invasive strategies,
* such as increasing shared_buffers to absorb the extra space.
*
- * Returns the (real, assumed or config provided) page size into *hugepagesize,
- * and the hugepage-related mmap flags to use into *mmap_flags.
+ * Returns the (real, assumed or config provided) page size into
+ * *hugepagesize, and the hugepage-related mmap flags to use into
+ * *mmap_flags if requested by the caller. If huge pages are not supported,
+ * *hugepagesize and *mmap_flags are set to 0.
*/
-static void
+void
GetHugePageSize(Size *hugepagesize, int *mmap_flags)
{
+#ifdef MAP_HUGETLB
+
Size default_hugepagesize = 0;
+ Size hugepagesize_local = 0;
+ int mmap_flags_local = 0;
/*
* System-dependent code to find out the default huge page size.
@@ -519,12 +523,12 @@ GetHugePageSize(Size *hugepagesize, int *mmap_flags)
if (huge_page_size != 0)
{
/* If huge page size is requested explicitly, use that. */
- *hugepagesize = (Size) huge_page_size * 1024;
+ hugepagesize_local = (Size) huge_page_size * 1024;
}
else if (default_hugepagesize != 0)
{
/* Otherwise use the system default, if we have it. */
- *hugepagesize = default_hugepagesize;
+ hugepagesize_local = default_hugepagesize;
}
else
{
@@ -536,26 +540,39 @@ GetHugePageSize(Size *hugepagesize, int *mmap_flags)
* writing, there are no reports of any non-Linux systems being picky
* about that.
*/
- *hugepagesize = 2 * 1024 * 1024;
+ hugepagesize_local = 2 * 1024 * 1024;
}
- *mmap_flags = MAP_HUGETLB;
+ mmap_flags_local = MAP_HUGETLB;
/*
* On recent enough Linux, also include the explicit page size, if
* necessary.
*/
#if defined(MAP_HUGE_MASK) && defined(MAP_HUGE_SHIFT)
- if (*hugepagesize != default_hugepagesize)
+ if (hugepagesize_local != default_hugepagesize)
{
- int shift = pg_ceil_log2_64(*hugepagesize);
+ int shift = pg_ceil_log2_64(hugepagesize_local);
- *mmap_flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
+ mmap_flags_local |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
}
#endif
-}
+
+ /* assign the results found */
+ if (mmap_flags)
+ *mmap_flags = mmap_flags_local;
+ if (hugepagesize)
+ *hugepagesize = hugepagesize_local;
+
+#else
+
+ if (hugepagesize)
+ *hugepagesize = 0;
+ if (mmap_flags)
+ *mmap_flags = 0;
#endif /* MAP_HUGETLB */
+}
/*
* Creates an anonymous mmap()ed shared memory segment.
diff --git a/src/backend/port/win32_shmem.c b/src/backend/port/win32_shmem.c
index d7a71992d81..64fde8de8f0 100644
--- a/src/backend/port/win32_shmem.c
+++ b/src/backend/port/win32_shmem.c
@@ -605,3 +605,17 @@ pgwin32_ReserveSharedMemoryRegion(HANDLE hChild)
return true;
}
+
+/*
+ * This function is provided for consistency with sysv_shmem.c and does not
+ * provide any useful information for Windows. To obtain the large page size,
+ * use GetLargePageMinimum() instead.
+ */
+void
+GetHugePageSize(Size *hugepagesize, int *mmap_flags)
+{
+ if (hugepagesize)
+ *hugepagesize = 0;
+ if (mmap_flags)
+ *mmap_flags = 0;
+}
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 13f3926ff67..9fa3e0631e6 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -326,6 +326,7 @@ InitializeShmemGUCs(void)
char buf[64];
Size size_b;
Size size_mb;
+ Size hp_size;
/*
* Calculate the shared memory size and round up to the nearest megabyte.
@@ -334,4 +335,17 @@ InitializeShmemGUCs(void)
size_mb = add_size(size_b, (1024 * 1024) - 1) / (1024 * 1024);
sprintf(buf, "%zu", size_mb);
SetConfigOption("shared_memory_size", buf, PGC_INTERNAL, PGC_S_OVERRIDE);
+
+ /*
+ * Calculate the number of huge pages required.
+ */
+ GetHugePageSize(&hp_size, NULL);
+ if (hp_size != 0)
+ {
+ Size hp_required;
+
+ hp_required = add_size(size_b / hp_size, 1);
+ sprintf(buf, "%zu", hp_required);
+ SetConfigOption("shared_memory_size_in_huge_pages", buf, PGC_INTERNAL, PGC_S_OVERRIDE);
+ }
}
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index a6e4fcc24ed..d2ce4a84506 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -665,6 +665,7 @@ static int max_identifier_length;
static int block_size;
static int segment_size;
static int shared_memory_size_mb;
+static int shared_memory_size_in_huge_pages;
static int wal_block_size;
static bool data_checksums;
static bool integer_datetimes;
@@ -2350,6 +2351,17 @@ static struct config_int ConfigureNamesInt[] =
},
{
+ {"shared_memory_size_in_huge_pages", PGC_INTERNAL, PRESET_OPTIONS,
+ gettext_noop("Shows the number of huge pages needed for the main shared memory area."),
+ gettext_noop("-1 indicates that the value could not be determined."),
+ GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE | GUC_RUNTIME_COMPUTED
+ },
+ &shared_memory_size_in_huge_pages,
+ -1, -1, INT_MAX,
+ NULL, NULL, NULL
+ },
+
+ {
{"temp_buffers", PGC_USERSET, RESOURCES_MEM,
gettext_noop("Sets the maximum number of temporary buffers used by each session."),
NULL,
diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h
index 059df1b72c2..518eb860657 100644
--- a/src/include/storage/pg_shmem.h
+++ b/src/include/storage/pg_shmem.h
@@ -87,5 +87,6 @@ extern PGShmemHeader *PGSharedMemoryCreate(Size size,
PGShmemHeader **shim);
extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2);
extern void PGSharedMemoryDetach(void);
+extern void GetHugePageSize(Size *hugepagesize, int *mmap_flags);
#endif /* PG_SHMEM_H */
generated by cgit v1.2.3 (git 2.25.1) at 2025-08-05 12:06:45 +0000