Commit 5b88a17c authored Feb 28, 2019 by Christoph Hellwig Committed by Jens Axboe Feb 28, 2019

block: optimize bvec iteration in bvec_iter_advance



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 shaving off a few cycles of the I/O hot path.

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 594b9a89

include/linux/bvec.h

+4 −3

Original line number	Diff line number	Diff line
		@@ -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++;
		}

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