Commit 4125bf76 authored by Chris Mason's avatar Chris Mason
Browse files

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: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 0be2e981
...@@ -1750,7 +1750,8 @@ static void end_bio_extent_writepage(struct bio *bio, int err) ...@@ -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) static void end_bio_extent_readpage(struct bio *bio, int err)
{ {
int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 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; struct extent_io_tree *tree;
u64 start; u64 start;
u64 end; u64 end;
...@@ -1773,7 +1774,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err) ...@@ -1773,7 +1774,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
else else
whole_page = 0; whole_page = 0;
if (--bvec >= bio->bi_io_vec) if (++bvec <= bvec_end)
prefetchw(&bvec->bv_page->flags); prefetchw(&bvec->bv_page->flags);
if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) { 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) ...@@ -1818,7 +1819,7 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
} }
check_page_locked(tree, page); check_page_locked(tree, page);
} }
} while (bvec >= bio->bi_io_vec); } while (bvec <= bvec_end);
bio_put(bio); bio_put(bio);
} }
......
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