From f2a09da9d0cba17ad4041e7e54f1ca840b12d0be Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Thu, 25 Jul 2013 19:22:33 +0800 Subject: [PATCH] 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 Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- 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 5d31f80c0562..0297f6f4d4c3 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); -- 2.39.5