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Btrfs: add branch prediction hints in the read page end IO function

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This patch add some branch prediction hints into the end IO function
of the read page, it reduced the percentage of the branch misses from
5.5% to 4.9%.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Miao Xie 2013-07-25 19:22:33 +08:00 committed by Chris Mason
parent 09a7f7a289
commit f2a09da9d0
1 changed files with 9 additions and 5 deletions
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14
fs/btrfs/extent_io.c
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@ -2502,7 +2502,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
spin_lock(&tree->lock);
state = find_first_extent_bit_state(tree, start, EXTENT_LOCKED);
if (state && state->start == start) {
if (likely(state && state->start == start)) {
/*
* take a reference on the state, unlock will drop
* the ref
@ -2512,7 +2512,8 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
spin_unlock(&tree->lock);
mirror = io_bio->mirror_num;
if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {
if (likely(uptodate && tree->ops &&
tree->ops->readpage_end_io_hook)) {
ret = tree->ops->readpage_end_io_hook(page, start, end,
state, mirror);
if (ret)
@ -2521,12 +2522,15 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
clean_io_failure(start, page);
}
if (!uptodate && tree->ops && tree->ops->readpage_io_failed_hook) {
if (likely(uptodate))
goto readpage_ok;
if (tree->ops && tree->ops->readpage_io_failed_hook) {
ret = tree->ops->readpage_io_failed_hook(page, mirror);
if (!ret && !err &&
test_bit(BIO_UPTODATE, &bio->bi_flags))
uptodate = 1;
} else if (!uptodate) {
} else {
/*
* The generic bio_readpage_error handles errors the
* following way: If possible, new read requests are
@ -2547,7 +2551,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
continue;
}
}
readpage_ok:
if (uptodate && tree->track_uptodate) {
set_extent_uptodate(tree, start, end, &cached,
GFP_ATOMIC);