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From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>
Cc: Alexander Viro <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	Christoph Hellwig <[email protected]>,
	Matthew Wilcox <[email protected]>,
	Ming Lei <[email protected]>,
	Johannes Weiner <[email protected]>
Subject: Re: [RFC 0/2] nocopy bvec for direct IO
Date: Wed, 9 Dec 2020 09:53:49 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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.

-- 
Jens Axboe


  parent reply	other threads:[~2020-12-09 16:55 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 [this message]
2020-12-13 22:03   ` Pavel Begunkov
2020-12-09 17:06 ` Al Viro

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