On Tue, Jun 13, 2023 at 02:50:30PM +0900, Michael Paquier wrote:
> On Mon, Jun 12, 2023 at 02:37:15PM -0700, Nathan Bossart wrote:
> > Fair enough. I know I've been waffling in the GUC versus function
> > discussion, but FWIW v7 of the patch looks reasonable to me.
>
> + Assert(strcmp("unknown", GetConfigOption("huge_pages_status", false,
> false)) != 0);
>
> Not sure that there is anything to gain with this assertion in
> CreateSharedMemoryAndSemaphores(), because this is pretty much what
> check_GUC_init() looks after?
It seems like you misread the assertion, so I added a comment about it.
Indeed, the assertion addresses the other question you asked later.
That's what I already commented about, and the reason I found it
compelling not to use a boolean.
On Thu, Apr 06, 2023 at 04:57:58PM -0500, Justin Pryzby wrote:
> I added an assert to check that a running server won't output
> "unknown".
On Wed, Jun 14, 2023 at 09:15:35AM +0900, Michael Paquier wrote:
> There was a second thing that bugged me here. Would it be worth
> adding some checks on huge_pages_status to make sure that it is never
> reported as unknown when the server is up and running?
--
Justin
>From 00234f5a0c14e2569ac1e7dab89907196f3ca9e1 Mon Sep 17 00:00:00 2001
From: Justin Pryzby <pryz...@telsasoft.com>
Date: Mon, 23 Jan 2023 18:33:51 -0600
Subject: [PATCH v8] add GUC: huge_pages_active
This is useful to show the current state of huge pages when
huge_pages=try. The effective status is not otherwise visible without
OS level tools like gdb or /proc/N/smaps.
https://www.postgresql.org/message-id/flat/tu4pr8401mb1152ebb0d271f827e2e37a01ee...@tu4pr8401mb1152.namprd84.prod.outlook.com
---
doc/src/sgml/config.sgml | 21 ++++++++++++++++++++-
src/backend/port/sysv_shmem.c | 10 ++++++++++
src/backend/port/win32_shmem.c | 5 +++++
src/backend/storage/ipc/ipci.c | 7 +++++++
src/backend/utils/misc/guc_tables.c | 20 ++++++++++++++++++++
src/include/storage/pg_shmem.h | 5 +++--
6 files changed, 65 insertions(+), 3 deletions(-)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 6262cb7bb2f..e69afae71bf 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1727,7 +1727,8 @@ include_dir 'conf.d'
server will try to request huge pages, but fall back to the default if
that fails. With <literal>on</literal>, failure to request huge pages
will prevent the server from starting up. With <literal>off</literal>,
- huge pages will not be requested.
+ huge pages will not be requested. The actual state of huge pages is
+ indicated by the server variable <xref linkend="guc-huge-pages-status"/>.
</para>
<para>
@@ -10738,6 +10739,24 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
</listitem>
</varlistentry>
+ <varlistentry id="guc-huge-pages-status" xreflabel="huge_pages_status">
+ <term><varname>huge_pages_status</varname> (<type>enum</type>)
+ <indexterm>
+ <primary><varname>huge_pages_status</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Reports the state of huge pages in the current instance:
+ <literal>on</literal>, <literal>off</literal>, or (if displayed with
+ <literal>postgres -C</literal>) <literal>unknown</literal>.
+ This parameter is useful to determine whether allocation of huge pages
+ was successful when <literal>huge_pages=try</literal>.
+ See <xref linkend="guc-huge-pages"/> for more information.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry id="guc-integer-datetimes" xreflabel="integer_datetimes">
<term><varname>integer_datetimes</varname> (<type>boolean</type>)
<indexterm>
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c
index eaba244bc9c..0e710237ea1 100644
--- a/src/backend/port/sysv_shmem.c
+++ b/src/backend/port/sysv_shmem.c
@@ -627,6 +627,10 @@ CreateAnonymousSegment(Size *size)
}
#endif
+ /* Report whether huge pages are in use */
+ SetConfigOption("huge_pages_status", ptr == MAP_FAILED ? "off" : "on",
+ PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT);
+
if (ptr == MAP_FAILED && huge_pages != HUGE_PAGES_ON)
{
/*
@@ -737,8 +741,14 @@ PGSharedMemoryCreate(Size size,
sysvsize = sizeof(PGShmemHeader);
}
else
+ {
sysvsize = size;
+ /* huge pages are only available with mmap */
+ SetConfigOption("huge_pages_status", "off",
+ PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT);
+ }
+
/*
* Loop till we find a free IPC key. Trust CreateDataDirLockFile() to
* ensure no more than one postmaster per data directory can enter this
diff --git a/src/backend/port/win32_shmem.c b/src/backend/port/win32_shmem.c
index 62e08074770..87f0b001915 100644
--- a/src/backend/port/win32_shmem.c
+++ b/src/backend/port/win32_shmem.c
@@ -327,6 +327,11 @@ retry:
Sleep(1000);
continue;
}
+
+ /* Report whether huge pages are in use */
+ SetConfigOption("huge_pages_status", (flProtect & SEC_LARGE_PAGES) ?
+ "on" : "off", PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT);
+
break;
}
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 8f1ded7338f..5901a3bd8eb 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -190,6 +190,13 @@ CreateSharedMemoryAndSemaphores(void)
*/
seghdr = PGSharedMemoryCreate(size, &shim);
+ /*
+ * Make sure that huge pages are never reported as "unknown"
+ * while the server is running.
+ */
+ Assert(strcmp("unknown",
+ GetConfigOption("huge_pages_status", false, false)) != 0);
+
InitShmemAccess(seghdr);
/*
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 977027ec8cb..37a97696dd5 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -365,6 +365,13 @@ static const struct config_enum_entry huge_pages_options[] = {
{NULL, 0, false}
};
+static const struct config_enum_entry huge_pages_status_options[] = {
+ {"off", HUGE_PAGES_OFF, false},
+ {"on", HUGE_PAGES_ON, false},
+ {"unknown", HUGE_PAGES_UNKNOWN, false},
+ {NULL, 0, false}
+};
+
static const struct config_enum_entry recovery_prefetch_options[] = {
{"off", RECOVERY_PREFETCH_OFF, false},
{"on", RECOVERY_PREFETCH_ON, false},
@@ -551,6 +558,8 @@ int ssl_renegotiation_limit;
int huge_pages = HUGE_PAGES_TRY;
int huge_page_size;
+int huge_pages_status = HUGE_PAGES_UNKNOWN;
+
/*
* These variables are all dummies that don't do anything, except in some
* cases provide the value for SHOW to display. The real state is elsewhere
@@ -4893,6 +4902,17 @@ struct config_enum ConfigureNamesEnum[] =
NULL, NULL, NULL
},
+ {
+ {"huge_pages_status", PGC_INTERNAL, PRESET_OPTIONS,
+ gettext_noop("Indicates the status of huge pages."),
+ NULL,
+ GUC_NOT_IN_SAMPLE | GUC_DISALLOW_IN_FILE
+ },
+ &huge_pages_status,
+ HUGE_PAGES_UNKNOWN, huge_pages_status_options,
+ NULL, NULL, NULL
+ },
+
{
{"recovery_prefetch", PGC_SIGHUP, WAL_RECOVERY,
gettext_noop("Prefetch referenced blocks during recovery."),
diff --git a/src/include/storage/pg_shmem.h b/src/include/storage/pg_shmem.h
index 4dd05f156d5..bfda42b0b26 100644
--- a/src/include/storage/pg_shmem.h
+++ b/src/include/storage/pg_shmem.h
@@ -46,12 +46,13 @@ extern PGDLLIMPORT int shared_memory_type;
extern PGDLLIMPORT int huge_pages;
extern PGDLLIMPORT int huge_page_size;
-/* Possible values for huge_pages */
+/* Possible values for huge_pages/huge_pages_status */
typedef enum
{
HUGE_PAGES_OFF,
HUGE_PAGES_ON,
- HUGE_PAGES_TRY
+ HUGE_PAGES_TRY, /* only for huge_pages */
+ HUGE_PAGES_UNKNOWN /* only for huge_pages_status */
} HugePagesType;
/* Possible values for shared_memory_type */
--
2.34.1
