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author | Mel Gorman <mgorman@suse.de> | 2011-04-27 15:26:56 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-04-28 11:28:21 -0700 |
commit | cc03638df20acbec5d0d0d9e07234aadde9e698d (patch) | |
tree | 462baff7982f3b58a647fc895ec3a62402e3d0b3 /include/sound/atmel-ac97c.h | |
parent | 1409f141ac719b994d2832911b1e9ec928943fc2 (diff) | |
download | kernel_samsung_espresso10-cc03638df20acbec5d0d0d9e07234aadde9e698d.zip kernel_samsung_espresso10-cc03638df20acbec5d0d0d9e07234aadde9e698d.tar.gz kernel_samsung_espresso10-cc03638df20acbec5d0d0d9e07234aadde9e698d.tar.bz2 |
mm: check if PTE is already allocated during page fault
With transparent hugepage support, handle_mm_fault() has to be careful
that a normal PMD has been established before handling a PTE fault. To
achieve this, it used __pte_alloc() directly instead of pte_alloc_map as
pte_alloc_map is unsafe to run against a huge PMD. pte_offset_map() is
called once it is known the PMD is safe.
pte_alloc_map() is smart enough to check if a PTE is already present
before calling __pte_alloc but this check was lost. As a consequence,
PTEs may be allocated unnecessarily and the page table lock taken. Thi
useless PTE does get cleaned up but it's a performance hit which is
visible in page_test from aim9.
This patch simply re-adds the check normally done by pte_alloc_map to
check if the PTE needs to be allocated before taking the page table lock.
The effect is noticable in page_test from aim9.
AIM9
2.6.38-vanilla 2.6.38-checkptenone
creat-clo 446.10 ( 0.00%) 424.47 (-5.10%)
page_test 38.10 ( 0.00%) 42.04 ( 9.37%)
brk_test 52.45 ( 0.00%) 51.57 (-1.71%)
exec_test 382.00 ( 0.00%) 456.90 (16.39%)
fork_test 60.11 ( 0.00%) 67.79 (11.34%)
MMTests Statistics: duration
Total Elapsed Time (seconds) 611.90 612.22
(While this affects 2.6.38, it is a performance rather than a functional
bug and normally outside the rules -stable. While the big performance
differences are to a microbench, the difference in fork and exec
performance may be significant enough that -stable wants to consider the
patch)
Reported-by: Raz Ben Yehuda <raziebe@gmail.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@kernel.org> [2.6.38.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/sound/atmel-ac97c.h')
0 files changed, 0 insertions, 0 deletions