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From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>,
	Matthew Wilcox <willy@infradead.org>,
	Ming Lei <ming.lei@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [RFC 0/2] nocopy bvec for direct IO
Date: Sun, 13 Dec 2020 22:03:44 +0000	[thread overview]
Message-ID: <b3edacbf-8501-8fcf-b492-2e4cc25c34d6@gmail.com> (raw)
In-Reply-To: <b165cd42-be79-69ed-ae06-a3f3ff633c62@kernel.dk>

On 09/12/2020 16:53, Jens Axboe wrote:
> On 12/8/20 7:19 PM, Pavel Begunkov wrote:
>> The idea is to avoid copying, merging, etc. bvec from iterator to bio
>> in direct I/O and use the one we've already got. Hook it up for io_uring.
>> Had an eye on it for a long, and it also was brought up by Matthew
>> just recently. Let me know if I forgot or misplaced some tags.
>>
>> A benchmark got me 430KIOPS vs 540KIOPS, or +25% on bare metal. And perf
>> shows that bio_iov_iter_get_pages() was taking ~20%. The test is pretty
>> silly, but still imposing. I'll redo it closer to reality for next
>> iteration, anyway need to double check some cases.
>>
>> If same applied to iomap, common chunck can be moved from block_dev
>> into bio_iov_iter_get_pages(), but if there any benefit for filesystems,
>> they should explicitly opt in with ITER_BVEC_FLAG_FIXED.
> 
> Ran this on a real device, and I get a 10% bump in performance with it.
> That's pretty amazing! So please do pursue this one and pull it to
> completion.

I'm curious, what block size did you use?

-- 
Pavel Begunkov

  reply	other threads:[~2020-12-13 22:08 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-09  2:19 [RFC 0/2] nocopy bvec for direct IO Pavel Begunkov
2020-12-09  2:19 ` [PATCH 1/2] iov: introduce ITER_BVEC_FLAG_FIXED Pavel Begunkov
2020-12-09  8:36   ` Christoph Hellwig
2020-12-09  9:06     ` Christoph Hellwig
2020-12-09 11:54       ` Pavel Begunkov
2020-12-09 13:07     ` Al Viro
2020-12-09 13:37       ` Pavel Begunkov
2020-12-09 17:55         ` Christoph Hellwig
2020-12-09 18:24           ` Matthew Wilcox
2020-12-13 22:09             ` Pavel Begunkov
2020-12-09  2:19 ` [PATCH 2/2] block: no-copy bvec for direct IO Pavel Begunkov
2020-12-09  8:40   ` Christoph Hellwig
2020-12-09 12:01     ` Pavel Begunkov
2020-12-09 12:05       ` Christoph Hellwig
2020-12-09 12:03         ` Pavel Begunkov
2020-12-11 14:06     ` Johannes Weiner
2020-12-11 14:20       ` Pavel Begunkov
2020-12-11 15:38         ` Johannes Weiner
2020-12-11 15:47           ` Pavel Begunkov
2020-12-11 16:13             ` Johannes Weiner
2020-12-09 21:13   ` David Laight
2020-12-09  6:50 ` [RFC 0/2] nocopy " Christoph Hellwig
2020-12-09 11:54   ` Pavel Begunkov
2020-12-09 16:53 ` Jens Axboe
2020-12-13 22:03   ` Pavel Begunkov [this message]
2020-12-09 17:06 ` Al Viro

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