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| author |   Pavel Begunkov <asml.silence@gmail.com> | 2021-01-09 16:03:03 +0000 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2021-01-25 08:58:24 -0700 |
| commit | c42bca92be928ce7dece5fc04cf68d0e37ee6718 (patch) | |
| tree | 132b3485f416fde3c9d57e9003f826fcb5583d75 /include/linux/bio.h | |
| parent | bio: add a helper calculating nr segments to alloc (diff) | |
| download | linux-dev-c42bca92be928ce7dece5fc04cf68d0e37ee6718.tar.xz linux-dev-c42bca92be928ce7dece5fc04cf68d0e37ee6718.zip | |
bio: don't copy bvec for direct IO
The block layer spends quite a while in blkdev_direct_IO() to copy and
initialise bio's bvec. However, if we've already got a bvec in the input
iterator it might be reused in some cases, i.e. when new
ITER_BVEC_FLAG_FIXED flag is set. Simple tests show considerable
performance boost, and it also reduces memory footprint.
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'include/linux/bio.h')
| -rw-r--r-- | include/linux/bio.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/bio.h b/include/linux/bio.h index 9ddb19801a03..676870b2c88d 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -444,10 +444,13 @@ static inline void bio_wouldblock_error(struct bio *bio) /* * Calculate number of bvec segments that should be allocated to fit data - * pointed by @iter. + * pointed by @iter. If @iter is backed by bvec it's going to be reused + * instead of allocating a new one. */ static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs) { + if (iov_iter_is_bvec(iter)) + return 0; return iov_iter_npages(iter, max_segs); } |