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help / color / mirror / Atom feedFrom: Andres Freund <[email protected]>
Subject: [PATCH v2 20/20] WIP: Use MAP_POPULATE
Date: Tue, 31 Dec 2024 13:25:56 -0500
For benchmarking it's quite annoying that the first time a memory is touched
has completely different perf characteristics than subsequent accesses. Using
MAP_POPULATE reduces that substantially.
---
src/backend/port/sysv_shmem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/backend/port/sysv_shmem.c b/src/backend/port/sysv_shmem.c
index a5a4511f66d..2a45dffd5e0 100644
--- a/src/backend/port/sysv_shmem.c
+++ b/src/backend/port/sysv_shmem.c
@@ -620,7 +620,7 @@ CreateAnonymousSegment(Size *size)
allocsize += hugepagesize - (allocsize % hugepagesize);
ptr = mmap(NULL, allocsize, PROT_READ | PROT_WRITE,
- PG_MMAP_FLAGS | mmap_flags, -1, 0);
+ PG_MMAP_FLAGS | MAP_POPULATE | mmap_flags, -1, 0);
mmap_errno = errno;
if (huge_pages == HUGE_PAGES_TRY && ptr == MAP_FAILED)
elog(DEBUG1, "mmap(%zu) with MAP_HUGETLB failed, huge pages disabled: %m",
--
2.45.2.746.g06e570c0df.dirty
--oy2jwuii6tssbict--
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