The patch titled
readahead: return early when readahead is disabled
has been added to the -mm tree. Its filename is
readahead-return-early-when-readahead-is-disabled.patch
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------------------------------------------------------
Subject: readahead: return early when readahead is disabled
From: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Reduce readahead overheads by returning early in do_sync_mmap_readahead().
tmpfs has ra_pages=0 and it can page fault really fast (not constraint by
IO if not swapping).
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Tested-by: Tim Chen <tim.c.chen@xxxxxxxxx>
Reported-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff -puN mm/filemap.c~readahead-return-early-when-readahead-is-disabled mm/filemap.c
--- a/mm/filemap.c~readahead-return-early-when-readahead-is-disabled
+++ a/mm/filemap.c
@@ -1567,6 +1567,8 @@ static void do_sync_mmap_readahead(struc
/* If we don't want any read-ahead, don't bother */
if (VM_RandomReadHint(vma))
return;
+ if (!ra->ra_pages)
+ return;
if (VM_SequentialReadHint(vma) ||
offset - 1 == (ra->prev_pos >> PAGE_CACHE_SHIFT)) {
@@ -1589,12 +1591,10 @@ static void do_sync_mmap_readahead(struc
* mmap read-around
*/
ra_pages = max_sane_readahead(ra->ra_pages);
- if (ra_pages) {
- ra->start = max_t(long, 0, offset - ra_pages/2);
- ra->size = ra_pages;
- ra->async_size = 0;
- ra_submit(ra, mapping, file);
- }
+ ra->start = max_t(long, 0, offset - ra_pages / 2);
+ ra->size = ra_pages;
+ ra->async_size = 0;
+ ra_submit(ra, mapping, file);
}
/*
_
Patches currently in -mm which might be from fengguang.wu@xxxxxxxxx are
mm-per-node-vmstat-show-proper-vmstats.patch
mm-per-node-vmstat-show-proper-vmstats-fix.patch
writeback-pass-writeback_control-down-to-move_expired_inodes.patch
writeback-introduce-writeback_controlinodes_cleaned.patch
writeback-try-more-writeback-as-long-as-something-was-written.patch
writeback-the-kupdate-expire-timestamp-should-be-a-moving-target.patch
writeback-sync-expired-inodes-first-in-background-writeback.patch
writeback-sync-expired-inodes-first-in-background-writeback-fix.patch
writeback-refill-b_io-iff-empty.patch
readahead-readahead-page-allocations-are-ok-to-fail.patch
readahead-return-early-when-readahead-is-disabled.patch
readahead-reduce-unnecessary-mmap_miss-increases.patch
readahead-trigger-mmap-sequential-readahead-on-pg_readahead.patch
--
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