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Add GUC parameter "huge_pages_status"

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This is useful to show the allocation state of huge pages when setting
up a server with "huge_pages = try", where allocating huge pages would
be attempted but the server would continue its startup sequence even if
the allocation fails.  The effective status of huge pages is not easily
visible without OS-level tools (or for instance, a lookup at
/proc/N/smaps), and the environments where Postgres runs may not
authorize that.  Like the other GUCs related to huge pages, this works
for Linux and Windows.

This GUC can report as values:
- "on", if huge pages were allocated.
- "off", if huge pages were not allocated.
- "unknown", a special state that could only be seen when using for
example postgres -C because it is only possible to know if the shared
memory allocation worked after we can check for the GUC values, even if
checking a runtime-computed GUC.  This value should never be seen when
querying for the GUC on a running server.  An assertion is added to
check that.

The discussion has also turned around having a new function to grab this
status, but this would have required more tricks for -DEXEC_BACKEND,
something that GUCs already handle.

Noriyoshi Shinoda has initiated the thread that has led to the result of
this commit.

Author: Justin Pryzby
Reviewed-by: Nathan Bossart, Kyotaro Horiguchi, Michael Paquier
Discussion: https://postgr.es/m/TU4PR8401MB1152EBB0D271F827E2E37A01EECC9@TU4PR8401MB1152.NAMPRD84.PROD.OUTLOOK.COM
This commit is contained in:
Michael Paquier
2023-07-06 14:42:36 +09:00
parent cf05113eb0
commit a14354cac0
8 changed files with 80 additions and 3 deletions
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14
src/backend/port/sysv_shmem.c
View File

@@ -627,6 +627,14 @@ CreateAnonymousSegment(Size *size)
}
#endif
/*
* Report whether huge pages are in use. This needs to be tracked before
* the second mmap() call if attempting to use huge pages failed
* previously.
*/
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 +745,14 @@ 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

5
src/backend/port/win32_shmem.c
View File

@@ -401,6 +401,11 @@ retry:
on_shmem_exit(pgwin32_SharedMemoryDelete, PointerGetDatum(hmap2));
*shim = hdr;
/* Report whether huge pages are in use */
SetConfigOption("huge_pages_status", (flProtect & SEC_LARGE_PAGES) ?
"on" : "off", PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT);
return hdr;
}

7
src/backend/storage/ipc/ipci.c
View File

@@ -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);
/*

19
src/backend/utils/misc/guc_tables.c
View File

@@ -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},
@@ -550,6 +557,7 @@ 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
@@ -4876,6 +4884,17 @@ 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."),