From: Christoph Hellwig <hch@infradead.org>
To: Pavel Begunkov <asml.silence@gmail.com>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 3/5] block: avoid extra iter advance with async iocb
Date: Mon, 25 Oct 2021 00:33:48 -0700 [thread overview]
Message-ID: <YXZd3ETk4P+OBWXD@infradead.org> (raw)
In-Reply-To: <aee615ac9cd6804c10c14938d011e0913f751960.1635006010.git.asml.silence@gmail.com>
On Sat, Oct 23, 2021 at 05:21:34PM +0100, Pavel Begunkov wrote:
> --- a/block/fops.c
> +++ b/block/fops.c
> @@ -352,11 +352,21 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
> bio->bi_end_io = blkdev_bio_end_io_async;
> bio->bi_ioprio = iocb->ki_ioprio;
>
> - ret = bio_iov_iter_get_pages(bio, iter);
> - if (unlikely(ret)) {
> - bio->bi_status = BLK_STS_IOERR;
> - bio_endio(bio);
> - return ret;
> + if (!iov_iter_is_bvec(iter)) {
> + ret = bio_iov_iter_get_pages(bio, iter);
> + if (unlikely(ret)) {
> + bio->bi_status = BLK_STS_IOERR;
> + bio_endio(bio);
> + return ret;
> + }
Nit: I generally find it much nicer to read if simple if statements
don't use pointless negations.
> + } else {
> + /*
> + * Users don't rely on the iterator being in any particular
> + * state for async I/O returning -EIOCBQUEUED, hence we can
> + * avoid expensive iov_iter_advance(). Bypass
> + * bio_iov_iter_get_pages() and set the bvec directly.
> + */
> + bio_iov_bvec_set(bio, iter);
So if this optimization is so useful, please also do it for
non-bvec iov_iters, which is what 99% of the applications actually
use.
next prev parent reply other threads:[~2021-10-25 7:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-23 16:21 [PATCH 0/5] block optimisations Pavel Begunkov
2021-10-23 16:21 ` [PATCH 1/5] block: add single bio async direct IO helper Pavel Begunkov
2021-10-23 16:21 ` [PATCH 2/5] block: refactor bio_iov_bvec_set() Pavel Begunkov
2021-10-25 7:31 ` Christoph Hellwig
2021-10-23 16:21 ` [PATCH 3/5] block: avoid extra iter advance with async iocb Pavel Begunkov
2021-10-25 7:33 ` Christoph Hellwig [this message]
2021-10-25 11:10 ` Pavel Begunkov
2021-10-23 16:21 ` [PATCH 4/5] block: kill unused polling bits in __blkdev_direct_IO() Pavel Begunkov
2021-10-23 16:46 ` Pavel Begunkov
2021-10-24 15:09 ` Jens Axboe
2021-10-24 17:17 ` Pavel Begunkov
2021-10-24 18:11 ` Jens Axboe
2021-10-25 7:35 ` Christoph Hellwig
2021-10-25 10:12 ` Pavel Begunkov
2021-10-25 10:27 ` Pavel Begunkov
2021-10-27 6:47 ` Christoph Hellwig
2021-10-23 16:21 ` [PATCH 5/5] block: add async version of bio_set_polled Pavel Begunkov
2021-10-25 7:36 ` Christoph Hellwig
2021-10-25 10:20 ` Pavel Begunkov
2021-10-25 7:28 ` [PATCH 0/5] block optimisations Christoph Hellwig
2021-10-26 23:30 ` (subset) " Jens Axboe
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