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Commit f2a09da9 authored by Miao Xie's avatar Miao Xie Committed by Chris Mason
Browse files

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: default avatarMiao Xie <miaox@cn.fujitsu.com>
Signed-off-by: default avatarJosef Bacik <jbacik@fusionio.com>
Signed-off-by: default avatarChris Mason <chris.mason@fusionio.com>
parent 09a7f7a2

fs/btrfs/extent_io.c

+9 −5
Original line number Diff line number Diff line
@@ -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);