| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 17/94] arm64: readahead: fault retry breaks mmap file read random detection | Date | Fri, 13 Nov 2015 10:09:11 +0000 |
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3.16.7-ckt20 -stable review patch. If anyone has any objections, please let me know.
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From: Mark Salyzyn <salyzyn@android.com>
commit 569ba74a7ba69f46ce2950bf085b37fea2408385 upstream.
This is the arm64 portion of commit 45cac65b0fcd ("readahead: fault retry breaks mmap file read random detection"), which was absent from the initial port and has since gone unnoticed. The original commit says:
> .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.
With this change, Mark reports that:
> 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.
Cc: Shaohua Li <shli@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Mark Salyzyn <salyzyn@android.com> Signed-off-by: Riley Andrews <riandrews@android.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.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 bcc965e2cce1..4e4a10df87c1 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -278,6 +278,7 @@ retry: * starvation. */ mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; + mm_flags |= FAULT_FLAG_TRIED; goto retry; } }
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