Messages in this thread Patch in this message | | | From | Mark Salyzyn <> | Subject | ARM64 readahead: fault retry breaks mmap file read random detection | Date | Mon, 21 Sep 2015 13:39:50 -0700 |
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Description from commit 45cac65b0fcd ("readahead: fault retry breaks mmap file read random detection")
.fault now can retry. The retry can break state machine of .fault. In filemap_fault, if page is miss, ra->mmap_miss is increased. In the second try, since the page is in page cache now, ra->mmap_miss is decreased. And these are done in one fault, so we can't detect random mmap file access.
Add a new flag to indicate .fault is tried once. In the second try, skip ra->mmap_miss decreasing. The filemap_fault state machine is ok with it.
I only tested x86, didn't test other archs, but looks the change for other archs is obvious, but who knows :)
< snip >
Yup, arm64 needs this too! Random read improves by 250%, sequential read improves by 40%, and random write by 400% to an eMMC device with dm crypto wrapped around it.
Signed-off-by: Mark Salyzyn <salyzyn@android.com> Signed-off-by: Riley Andrews <riandrews@android.com> Cc: Shaohua Li <shli@kernel.org> Cc: Shaohua Li <shaohua.li@fusionio.com> Cc: Rik van Riel <riel@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> --- arch/arm64/mm/fault.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index aba9ead..9fadf6d 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -287,6 +287,7 @@ retry: * starvation. */ mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; + mm_flags |= FAULT_FLAG_TRIED; goto retry; } } -- 2.6.0.rc0.131.gf624c3d
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