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From: Kent Overstreet <kent.overstreet@gmail.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, Coly Li <colyli@suse.de>,
	Christoph Hellwig <hch@infradead.org>,
	Keith Busch <kbusch@kernel.org>,
	linux-bcache@vger.kernel.org
Subject: Re: [PATCH V4] block: optimize for small block size IO
Date: Mon, 4 Nov 2019 13:14:03 -0500	[thread overview]
Message-ID: <20191104181403.GA8984@kmo-pixel> (raw)
In-Reply-To: <20191102072911.24817-1-ming.lei@redhat.com>

On Sat, Nov 02, 2019 at 03:29:11PM +0800, Ming Lei wrote:
> __blk_queue_split() may be a bit heavy for small block size(such as
> 512B, or 4KB) IO, so introduce one flag to decide if this bio includes
> multiple page. And only consider to try splitting this bio in case
> that the multiple page flag is set.

So, back in the day I had an alternative approach in mind: get rid of
blk_queue_split entirely, by pushing splitting down to the request layer - when
we map the bio/request to sgl, just have it map as much as will fit in the sgl
and if it doesn't entirely fit bump bi_remaining and leave it on the request
queue.

This would mean there'd be no need for counting segments at all, and would cut a
fair amount of code out of the io path.

  parent reply	other threads:[~2019-11-04 18:14 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-02  7:29 [PATCH V4] block: optimize for small block size IO Ming Lei
2019-11-02 14:03 ` Jens Axboe
2019-11-02 15:57   ` Jens Axboe
2019-11-04  0:01     ` Ming Lei
2019-11-04 18:14 ` Kent Overstreet [this message]
2019-11-04 18:15   ` Christoph Hellwig
2019-11-04 18:17     ` Kent Overstreet
2019-11-04 18:23       ` Jens Axboe
2019-11-04 18:42         ` Kent Overstreet
2019-11-05  1:11           ` Ming Lei
2019-11-05  2:11             ` Kent Overstreet
2019-11-05  2:20               ` Ming Lei
2019-11-05  2:30                 ` Kent Overstreet
2019-11-05  2:38                   ` Jens Axboe
2019-11-05  3:14                     ` Kent Overstreet
2019-11-05  3:33                       ` Jens Axboe
2019-11-05  2:46                   ` Ming Lei
2019-11-05  2:49                     ` Jens Axboe
2019-11-05  3:34                       ` Ming Lei
2019-11-05  0:44   ` Ming Lei

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