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>
static void end_bio_extent_readpage(struct bio *bio, int err)
{
int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
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;
struct extent_io_tree *tree;
u64 start;
u64 end;
- 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) {
prefetchw(&bvec->bv_page->flags);
if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {
}
check_page_locked(tree, page);
}
}
check_page_locked(tree, page);
}
- } while (bvec >= bio->bi_io_vec);
+ } while (bvec <= bvec_end);