The patch titled
Subject: shmem: avoid huge pages for small files
has been added to the -mm tree. Its filename is
shmem-avoid-huge-pages-for-small-files.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/shmem-avoid-huge-pages-for-small-files.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/shmem-avoid-huge-pages-for-small-files.patch
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From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: shmem: avoid huge pages for small files
Huge pages are detrimental for small file: they causes noticible overhead
on both allocation performance and memory footprint.
This patch aimed to address this issue by avoiding huge pages until file
grown to size of huge page. This would cover most of the cases where huge
pages causes regressions in performance.
Couple notes:
- if shmem_enabled is set to 'force', the limit is ignored. We still
want to generate as many pages as possible for functional testing.
- the limit doesn't affect khugepaged behaviour: it still can collapse
pages based on its settings;
Link: http://lkml.kernel.org/r/20161021224629.tnwuvruhblkg22qj@xxxxxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/transhuge.txt | 3 +++
mm/shmem.c | 5 +++++
2 files changed, 8 insertions(+)
diff -puN Documentation/vm/transhuge.txt~shmem-avoid-huge-pages-for-small-files Documentation/vm/transhuge.txt
--- a/Documentation/vm/transhuge.txt~shmem-avoid-huge-pages-for-small-files
+++ a/Documentation/vm/transhuge.txt
@@ -238,6 +238,9 @@ values:
- "force":
Force the huge option on for all - very useful for testing;
+To avoid overhead for small files, we don't allocate huge pages for a file
+until it grows to size of huge pages.
+
== Need of application restart ==
The transparent_hugepage/enabled values and tmpfs mount option only affect
diff -puN mm/shmem.c~shmem-avoid-huge-pages-for-small-files mm/shmem.c
--- a/mm/shmem.c~shmem-avoid-huge-pages-for-small-files
+++ a/mm/shmem.c
@@ -1692,6 +1692,11 @@ repeat:
goto alloc_huge;
/* TODO: implement fadvise() hints */
goto alloc_nohuge;
+ case SHMEM_HUGE_ALWAYS:
+ i_size = i_size_read(inode);
+ if (index < HPAGE_PMD_NR && i_size < HPAGE_PMD_SIZE)
+ goto alloc_nohuge;
+ break;
}
alloc_huge:
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
shmem-avoid-huge-pages-for-small-files.patch
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