From: Dave Chinner <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: [email protected], Jens Axboe <[email protected]>,
Christoph Hellwig <[email protected]>,
Matthew Wilcox <[email protected]>,
Ming Lei <[email protected]>,
Johannes Weiner <[email protected]>,
Alexander Viro <[email protected]>,
"Darrick J . Wong" <[email protected]>,
"Martin K . Petersen" <[email protected]>,
Jonathan Corbet <[email protected]>,
[email protected], [email protected],
[email protected], [email protected],
[email protected], [email protected],
[email protected]
Subject: Re: [PATCH v1 6/6] block/iomap: don't copy bvec for direct IO
Date: Tue, 15 Dec 2020 12:09:21 +1100 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <498b34d746627e874740d8315b2924880c46dbc3.1607976425.git.asml.silence@gmail.com>
On Tue, Dec 15, 2020 at 12:20:25AM +0000, Pavel Begunkov wrote:
> 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 <[email protected]>
> Signed-off-by: Pavel Begunkov <[email protected]>
> ---
> Documentation/filesystems/porting.rst | 9 ++++
> block/bio.c | 64 +++++++++++----------------
> include/linux/bio.h | 3 ++
> 3 files changed, 38 insertions(+), 38 deletions(-)
This doesn't touch iomap code, so the title of the patch seems
wrong...
> +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.
This is hard to follow. Perhaps:
bio_iov_iter_get_pages() uses the bvecs provided for bvec based
iterators rather than copying them. Hence anyone issuing kiocb based
IO needs to ensure the bvecs and pages stay referenced until the
submitted I/O is completed by a call to ->ki_complete() or returns
with an error other than -EIOCBQUEUED.
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 2a9f3f0bbe0a..337f4280b639 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -444,6 +444,9 @@ static inline void bio_wouldblock_error(struct bio *bio)
>
> static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs)
> {
> + /* reuse iter->bvec */
> + if (iov_iter_is_bvec(iter))
> + return 0;
> return iov_iter_npages(iter, max_segs);
Ah, I'm a blind idiot... :/
Cheers,
Dave.
--
Dave Chinner
[email protected]
next prev parent reply other threads:[~2020-12-15 1:10 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-15 0:20 [PATCH v1 0/6] no-copy bvec Pavel Begunkov
2020-12-15 0:20 ` [PATCH v1 1/6] target/file: allocate the bvec array as part of struct target_core_file_cmd Pavel Begunkov
2020-12-15 0:20 ` [PATCH v1 2/6] iov_iter: optimise bvec iov_iter_advance() Pavel Begunkov
2020-12-15 9:37 ` David Laight
2020-12-15 11:23 ` Pavel Begunkov
2020-12-15 13:54 ` David Laight
2020-12-15 13:56 ` Pavel Begunkov
2020-12-22 14:03 ` Christoph Hellwig
2020-12-15 0:20 ` [PATCH v1 3/6] bio: deduplicate adding a page into bio Pavel Begunkov
2020-12-22 14:04 ` Christoph Hellwig
2020-12-15 0:20 ` [PATCH v1 4/6] block/psi: remove PSI annotations from direct IO Pavel Begunkov
2020-12-15 0:56 ` Dave Chinner
2020-12-15 1:03 ` Pavel Begunkov
2020-12-15 1:33 ` Dave Chinner
2020-12-15 11:41 ` Pavel Begunkov
2020-12-22 14:07 ` Christoph Hellwig
2020-12-15 0:20 ` [PATCH v1 5/6] bio: add a helper calculating nr segments to alloc Pavel Begunkov
2020-12-15 1:00 ` Dave Chinner
2020-12-15 1:07 ` Pavel Begunkov
2020-12-15 1:09 ` Dave Chinner
2020-12-22 14:07 ` Christoph Hellwig
2020-12-15 0:20 ` [PATCH v1 6/6] block/iomap: don't copy bvec for direct IO Pavel Begunkov
2020-12-15 1:09 ` Dave Chinner [this message]
2020-12-15 1:15 ` Pavel Begunkov
2020-12-22 14:15 ` Christoph Hellwig
2020-12-15 1:41 ` [PATCH v1 0/6] no-copy bvec Ming Lei
2020-12-15 11:14 ` Pavel Begunkov
2020-12-15 12:03 ` Ming Lei
2020-12-15 14:05 ` Pavel Begunkov
2020-12-22 14:11 ` Christoph Hellwig
2020-12-23 12:52 ` Pavel Begunkov
2020-12-23 15:51 ` Christoph Hellwig
2020-12-23 16:04 ` James Bottomley
2020-12-23 20:23 ` Douglas Gilbert
2020-12-23 20:32 ` Pavel Begunkov
2020-12-24 6:41 ` Christoph Hellwig
2020-12-24 16:45 ` Douglas Gilbert
2020-12-24 17:30 ` James Bottomley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox