bio_for_each_bvec is used in fast path of bio splitting and sg mapping,
and what we want to do is to iterate over multi-page bvecs, instead of pages.
However, bvec_iter_advance() is invisble for this requirement, and
always advance by page size.
This way isn't efficient for multipage bvec iterator, also bvec_iter_len()
isn't as fast as mp_bvec_iter_len().
So advance by multi-page bvec's length instead of page size for bio_for_each_bvec().
More than 1% IOPS improvement can be observed in io_uring test on null_blk.
Cc: Omar Sandoval <osandov@xxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
include/linux/bio.h | 13 +++++++++----
include/linux/bvec.h | 13 ++++++++++---
2 files changed, 19 insertions(+), 7 deletions(-)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index bb6090aa165d..29c7dd348dc2 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -134,17 +134,22 @@ static inline bool bio_full(struct bio *bio)
for (i = 0, iter_all.idx = 0; iter_all.idx < (bio)->bi_vcnt; iter_all.idx++) \
mp_bvec_for_each_segment(bvl, &((bio)->bi_io_vec[iter_all.idx]), i, iter_all)
-static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
- unsigned bytes)
+static inline void __bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
+ unsigned bytes, bool bvec)
{
iter->bi_sector += bytes >> 9;
if (bio_no_advance_iter(bio))
iter->bi_size -= bytes;
else
- bvec_iter_advance(bio->bi_io_vec, iter, bytes);
+ __bvec_iter_advance(bio->bi_io_vec, iter, bytes, bvec);
/* TODO: It is reasonable to complete bio with error here. */
}
+static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
+ unsigned bytes)
+{
+ return __bio_advance_iter(bio, iter, bytes, false);
+}
#define __bio_for_each_segment(bvl, bio, iter, start) \
for (iter = (start); \
@@ -159,7 +164,7 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
for (iter = (start); \
(iter).bi_size && \
((bvl = mp_bvec_iter_bvec((bio)->bi_io_vec, (iter))), 1); \
- bio_advance_iter((bio), &(iter), (bvl).bv_len))
+ __bio_advance_iter((bio), &(iter), (bvl).bv_len, true))
/* iterate over multi-page bvec */
#define bio_for_each_bvec(bvl, bio, iter) \
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 2c32e3e151a0..98a140fa4dac 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -102,8 +102,8 @@ static inline struct page *bvec_nth_page(struct page *page, int idx)
.bv_offset = bvec_iter_offset((bvec), (iter)), \
})
-static inline bool bvec_iter_advance(const struct bio_vec *bv,
- struct bvec_iter *iter, unsigned bytes)
+static inline bool __bvec_iter_advance(const struct bio_vec *bv,
+ struct bvec_iter *iter, unsigned bytes, bool bvec)
{
if (WARN_ONCE(bytes > iter->bi_size,
"Attempted to advance past end of bvec iter\n")) {
@@ -112,7 +112,8 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
}
while (bytes) {
- unsigned iter_len = bvec_iter_len(bv, *iter);
+ unsigned iter_len = bvec ? mp_bvec_iter_len(bv, *iter) :
+ bvec_iter_len(bv, *iter);
unsigned len = min(bytes, iter_len);
bytes -= len;
@@ -127,6 +128,12 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
return true;
}
+static inline bool bvec_iter_advance(const struct bio_vec *bv,
+ struct bvec_iter *iter, unsigned bytes)
+{
+ return __bvec_iter_advance(bv, iter, bytes, false);
+}
+
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
--
2.9.5
