There is no need to only iterate in chunks of PAGE_SIZE or less in
bvec_iter_advance, given that the callers pass in the chunk length that
they are operating on - either that already is less than PAGE_SIZE
because they do classic page-based iteration, or it is larger because
the caller operates on multi-page bvecs.
This should help optimizing shaving off a few cycles of the I/O hot
path.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
include/linux/bvec.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 2c32e3e151a0..cf06c0647c4f 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -112,14 +112,15 @@ static inline bool bvec_iter_advance(const struct bio_vec *bv,
}
while (bytes) {
- unsigned iter_len = bvec_iter_len(bv, *iter);
- unsigned len = min(bytes, iter_len);
+ const struct bio_vec *cur = bv + iter->bi_idx;
+ unsigned len = min3(bytes, iter->bi_size,
+ cur->bv_len - iter->bi_bvec_done);
bytes -= len;
iter->bi_size -= len;
iter->bi_bvec_done += len;
- if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
+ if (iter->bi_bvec_done == cur->bv_len) {
iter->bi_bvec_done = 0;
iter->bi_idx++;
}
--
2.20.1
