From: Mark Salyzyn <[email protected]>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
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 <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Wu Fengguang <[email protected]>
Signed-off-by: Mark Salyzyn <[email protected]>
Signed-off-by: Riley Andrews <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
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 c23751b06120..cc083b6e4ce7 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;
}
}
--
2.6.2
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