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block: introduce bvec_nth_page()

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Single-page bvec can often be seen in small BS workloads, so
introduce bvec_nth_page() for avoiding to call nth_page() unnecessarily,
which looks not cheap.

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 20:40:10 +08:00 committed by Jens Axboe
parent 81214bab58
commit 4d633062c1
2 changed files with 9 additions and 4 deletions
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2
block/blk-merge.c
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@ -483,7 +483,7 @@ static unsigned blk_bvec_map_sg(struct request_queue *q,
offset = (total + bvec->bv_offset) % PAGE_SIZE;
idx = (total + bvec->bv_offset) / PAGE_SIZE;
pg = nth_page(bvec->bv_page, idx);
pg = bvec_nth_page(bvec->bv_page, idx);
sg_set_page(*sg, pg, seg_size, offset);

11
include/linux/bvec.h
View File

@ -51,6 +51,11 @@ struct bvec_iter_all {
unsigned done;
};
static inline struct page *bvec_nth_page(struct page *page, int idx)
{
return idx == 0 ? page : nth_page(page, idx);
}
/*
* various member access, note that bio_data should of course not be used
* on highmem page vectors
@ -87,8 +92,8 @@ struct bvec_iter_all {
PAGE_SIZE - bvec_iter_offset((bvec), (iter)))
#define bvec_iter_page(bvec, iter) \
nth_page(mp_bvec_iter_page((bvec), (iter)), \
mp_bvec_iter_page_idx((bvec), (iter)))
bvec_nth_page(mp_bvec_iter_page((bvec), (iter)), \
mp_bvec_iter_page_idx((bvec), (iter)))
#define bvec_iter_bvec(bvec, iter) \
((struct bio_vec) { \
@ -171,7 +176,7 @@ static inline void mp_bvec_last_segment(const struct bio_vec *bvec,
unsigned total = bvec->bv_offset + bvec->bv_len;
unsigned last_page = (total - 1) / PAGE_SIZE;
seg->bv_page = nth_page(bvec->bv_page, last_page);
seg->bv_page = bvec_nth_page(bvec->bv_page, last_page);
/* the whole segment is inside the last page */
if (bvec->bv_offset >= last_page * PAGE_SIZE) {