Btrfs: add branch prediction hints in the read page end IO function
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>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 5d31f80..0297f6f 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2502,7 +2502,7 @@
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 @@
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 @@
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 @@
continue;
}
}
-
+readpage_ok:
if (uptodate && tree->track_uptodate) {
set_extent_uptodate(tree, start, end, &cached,
GFP_ATOMIC);