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block: optimize blk_bio_segment_split for single-page bvec

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Introduce a fast path for single-page bvec IO, then we can avoid
to call bvec_split_segs() unnecessarily.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2019-02-27 20:40:12 +08:00 committed by Jens Axboe
parent 48d7727cae
commit bbcbbd567c
1 changed files with 9 additions and 3 deletions
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12
block/blk-merge.c
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@ -286,10 +286,16 @@ new_segment:
bvprv = bv;
bvprvp = &bvprv;
if (bvec_split_segs(q, &bv, &nsegs, &seg_size,
&front_seg_size, &sectors))
if (bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
nsegs++;
seg_size = bv.bv_len;
sectors += bv.bv_len >> 9;
if (nsegs == 1 && seg_size > front_seg_size)
front_seg_size = seg_size;
} else if (bvec_split_segs(q, &bv, &nsegs, &seg_size,
&front_seg_size, &sectors)) {
goto split;
}
}
do_split = false;