diff options
| author | Chris Mason <chris.mason@oracle.com> | 2010-02-03 21:18:45 +0300 |
|---|---|---|
| committer | Chris Mason <chris.mason@oracle.com> | 2010-03-15 18:00:12 +0300 |
| commit | 4125bf761cd0786e1163e024c7c809ce2cc625bc (patch) | |
| tree | 3e1b73b0db29994e8fb56c727c38c1167922f189 | |
| parent | 0be2e98173f8badd5ccc7c2e994891746ba1caf4 (diff) | |
| download | linux-4125bf761cd0786e1163e024c7c809ce2cc625bc.tar.xz | |
Btrfs: finish read pages in the order they are submitted
The endio is done at reverse order of bio vectors.
That means for a sequential read, the page first submitted will finish
last in a bio. Considering we will do checksum (making cache hot) for
every page, this does introduce delay (and chance to squeeze cache used
soon) for pages submitted at the begining.
I don't observe obvious performance difference with below patch at my
simple test, but seems more natural to finish read in the order they are
submitted.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
| -rw-r--r-- | fs/btrfs/extent_io.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 7073cbb1b2d4..355a973719a0 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1750,7 +1750,8 @@ static void end_bio_extent_writepage(struct bio *bio, int err) static void end_bio_extent_readpage(struct bio *bio, int err) { int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); - struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1; + struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1; + struct bio_vec *bvec = bio->bi_io_vec; struct extent_io_tree *tree; u64 start; u64 end; @@ -1773,7 +1774,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err) else whole_page = 0; - if (--bvec >= bio->bi_io_vec) + if (++bvec <= bvec_end) prefetchw(&bvec->bv_page->flags); if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) { @@ -1818,7 +1819,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err) } check_page_locked(tree, page); } - } while (bvec >= bio->bi_io_vec); + } while (bvec <= bvec_end); bio_put(bio); } |