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 <saly...@android.com>
Signed-off-by: Riley Andrews <riandr...@android.com>
Cc: Shaohua Li <s...@kernel.org>
Cc: Shaohua Li <shaohua...@fusionio.com>
Cc: Rik van Riel <r...@redhat.com>
Cc: Wu Fengguang <fengguang...@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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