From: Jens Axboe <axboe@kernel.dk>
To: Christoph Hellwig <hch@infradead.org>, Ming Lei <ming.lei@redhat.com>
Cc: linux-block@vger.kernel.org, Omar Sandoval <osandov@fb.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] block: advance by bvec's length for bio_for_each_bvec
Date: Thu, 28 Feb 2019 08:23:23 -0700 [thread overview]
Message-ID: <22539865-7c66-2d2d-2304-cd09f2a86064@kernel.dk> (raw)
In-Reply-To: <20190228135832.GA3182@infradead.org>
On 2/28/19 6:58 AM, Christoph Hellwig wrote:
> On Thu, Feb 28, 2019 at 11:24:21AM +0800, Ming Lei wrote:
>> bio_for_each_bvec is used in fast path of bio splitting and sg mapping,
>> and what we want to do is to iterate over multi-page bvecs, instead of pages.
>> However, bvec_iter_advance() is invisble for this requirement, and
>> always advance by page size.
>>
>> This way isn't efficient for multipage bvec iterator, also bvec_iter_len()
>> isn't as fast as mp_bvec_iter_len().
>>
>> So advance by multi-page bvec's length instead of page size for bio_for_each_bvec().
>>
>> More than 1% IOPS improvement can be observed in io_uring test on null_blk.
>
> We've been there before, and I still insist that there is not good
> reason ever to clamp the iteration to page size in bvec_iter_advance.
> Callers that iterate over it already do that in the callers.
>
> So here is a resurretion and rebase of my patch from back then to
> just do the right thing:
Care to resend as a proper patch?
--
Jens Axboe
prev parent reply other threads:[~2019-02-28 15:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-28 3:24 [PATCH] block: advance by bvec's length for bio_for_each_bvec Ming Lei
2019-02-28 13:00 ` Jens Axboe
2019-02-28 13:58 ` Christoph Hellwig
2019-02-28 15:20 ` Ming Lei
2019-02-28 15:23 ` Jens Axboe [this message]
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