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Date: Fri, 8 Jul 2022 07:38:49 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Julien Rouhaud <rjuju123@gmail.com>
Cc: Wilm Hoyer <W.Hoyer@dental-vision.de>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: BUG #17448: In Windows 10, version 1703 and later, huge_pages
 doesn't work.
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On Tue, Apr 26, 2022 at 12:54:35PM +0800, Julien Rouhaud wrote:
> Their API is entirely useless, so I'm still on the opinion that we should
> unconditionally use the FILE_MAP_LARGE_PAGES flag if it's defined and call it a
> day.

Now that the minimal runtime version is Windows 10 in v16~ thanks to
495ed0e, we could be much more aggressive and do the attached, which
is roughly what Thomas has proposed upthread at the exception of
assuming that FILE_MAP_LARGE_PAGES always exists, because updates are
forced by MS in this environment.  We could make it conditional, of
course, with an extra #ifdef painting.
--
Michael

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=46rom 9a1450ecbe291cfc92e97f49506db9f443c8cbe9 Mon Sep 17 00:00:00 2001
=46rom: Michael Paquier <michael@paquier.xyz>
Date: Thu, 7 Jul 2022 16:51:18 +0900
Subject: [PATCH v2] Fix huge_pages on current Windows.

Since Windows 10 1703, it's necessary to pass a flag to MapViewOfFile()
to enable large pages at map time.

Reported-by: Okano Naoki
Author: Thomas Munro
Discussion: https://postgr.es/m/17448-0a96583a67edb1f7%40postgresql.org
---
 src/backend/port/win32_shmem.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/backend/port/win32_shmem.c b/src/backend/port/win32_shmem.c
index 6cf69411db..2f51da5a6a 100644
--- a/src/backend/port/win32_shmem.c
+++ b/src/backend/port/win32_shmem.c
@@ -216,6 +216,7 @@ PGSharedMemoryCreate(Size size,
 	SIZE_T		largePageSize =3D 0;
 	Size		orig_size =3D size;
 	DWORD		flProtect =3D PAGE_READWRITE;
+	DWORD		desiredAccess;
=20
 	ShmemProtectiveRegion =3D VirtualAlloc(NULL, PROTECTIVE_REGION_SIZE,
 										 MEM_RESERVE, PAGE_NOACCESS);
@@ -353,12 +354,17 @@ retry:
 	if (!CloseHandle(hmap))
 		elog(LOG, "could not close handle to shared memory: error code %lu", Get=
LastError());
=20
+	desiredAccess =3D FILE_MAP_WRITE | FILE_MAP_READ;
+
+	/* Set large pages if wanted. */
+	if ((flProtect & SEC_LARGE_PAGES) !=3D 0)
+		desiredAccess |=3D FILE_MAP_LARGE_PAGES;
=20
 	/*
 	 * Get a pointer to the new shared memory segment. Map the whole segment
 	 * at once, and let the system decide on the initial address.
 	 */
-	memAddress =3D MapViewOfFileEx(hmap2, FILE_MAP_WRITE | FILE_MAP_READ, 0, =
0, 0, NULL);
+	memAddress =3D MapViewOfFileEx(hmap2, desiredAccess, 0, 0, 0, NULL);
 	if (!memAddress)
 		ereport(FATAL,
 				(errmsg("could not create shared memory segment: error code %lu", GetL=
astError()),
--=20
2.36.1


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