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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 /Documentation/filesystems | |
| 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 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/porting.rst | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index c722d94f29ea..1f8cf8e10b34 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -872,3 +872,12 @@ its result is kern_unmount() or kern_unmount_array(). zero-length bvec segments are disallowed, they must be filtered out before passed on to an iterator. + +--- + +**mandatory** + +For bvec based itererators bio_iov_iter_get_pages() now doesn't copy bvecs but +uses the one provided. Anyone issuing kiocb-I/O should ensure that the bvec and +page references stay until I/O has completed, i.e. until ->ki_complete() has +been called or returned with non -EIOCBQUEUED code. |