From: Christoph Hellwig <hch@infradead.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Coly Li <colyli@suse.de>,
Keith Busch <kbusch@kernel.org>,
linux-bcache@vger.kernel.org
Subject: Re: [PATCH V3] block: optimize for small block size IO
Date: Wed, 30 Oct 2019 06:54:26 -0700 [thread overview]
Message-ID: <20191030135426.GA24655@infradead.org> (raw)
In-Reply-To: <20191030002126.GA14423@ming.t460p>
On Wed, Oct 30, 2019 at 08:21:26AM +0800, Ming Lei wrote:
> > + if ((*bio)->bi_vcnt == 1 &&
> > + (*bio)->bi_io_vec[0].bv_len <= PAGE_SIZE) {
> > + *nr_segs = 1;
> > + return;
> > + }
> > split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs);
> > break;
> > }
>
> This bio(*bio) may be a fast-cloned bio from somewhere(DM, MD, ...), so the above
> check can't work sometime.
Please explain how it doesn't work. In the worse case it will give us
a false negastive, that is we don't take the fast path when in theory
we could, but then again fast cloneѕ bios will have so much overhead
that it should not matter.
next prev parent reply other threads:[~2019-10-30 13:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-29 10:51 [PATCH V3] block: optimize for small block size IO Ming Lei
2019-10-29 11:04 ` Christoph Hellwig
2019-10-29 15:11 ` Jens Axboe
2019-10-30 0:21 ` Ming Lei
2019-10-30 13:54 ` Christoph Hellwig [this message]
2019-10-31 1:33 ` Ming Lei
2019-10-29 15:09 ` Bart Van Assche
2019-11-01 14:47 ` Jens Axboe
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