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@xxxxxxxxxxxxxx>
---
Changelog v1 -> v2:
- Just change the description in the changelog
---
fs/btrfs/extent_io.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a722235..6b6ba1a 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -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);
--
1.8.1.4
--
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