From: Jens Axboe <axboe@kernel.dk>
To: Matthew Wilcox <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>, Christoph Hellwig <hch@lst.de>,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC] what to do with IOCB_DSYNC?
Date: Mon, 23 May 2022 09:55:22 -0600 [thread overview]
Message-ID: <ef4d18ee-1c3e-2bd6-eff5-344a0359884d@kernel.dk> (raw)
In-Reply-To: <YoutEnMCVdwlzboT@casper.infradead.org>
On 5/23/22 9:49 AM, Matthew Wilcox wrote:
> On Mon, May 23, 2022 at 09:44:12AM -0600, Jens Axboe wrote:
>> On 5/23/22 9:12 AM, Jens Axboe wrote:
>>>> Current branch pushed to #new.iov_iter (at the moment; will rename
>>>> back to work.iov_iter once it gets more or less stable).
>>>
>>> Sounds good, I'll see what I need to rebase.
>>
>> On the previous branch, ran a few quick numbers. dd from /dev/zero to
>> /dev/null, with /dev/zero using ->read() as it does by default:
>>
>> 32 260MB/sec
>> 1k 6.6GB/sec
>> 4k 17.9GB/sec
>> 16k 28.8GB/sec
>>
>> now comment out ->read() so it uses ->read_iter() instead:
>>
>> 32 259MB/sec
>> 1k 6.6GB/sec
>> 4k 18.0GB/sec
>> 16k 28.6GB/sec
>>
>> which are roughly identical, all things considered. Just a sanity check,
>> but looks good from a performance POV in this basic test.
>>
>> Now let's do ->read_iter() but make iov_iter_zero() copy from the zero
>> page instead:
>>
>> 32 250MB/sec
>> 1k 7.7GB/sec
>> 4k 28.8GB/sec
>> 16k 71.2GB/sec
>>
>> Looks like it's a tad slower for 32-bytes, considerably better for 1k,
>> and massively better at page size and above. This is on an Intel 12900K,
>> so recent CPU. Let's try cacheline and above:
>>
>> Size Method BW
>> 64 copy_from_zero() 508MB/sec
>> 128 copy_from_zero() 1.0GB/sec
>> 64 clear_user() 513MB/sec
>> 128 clear_user() 1.0GB/sec
>
> See this thread-of-doom:
>
> https://lore.kernel.org/all/Ynq1nVpu1xCpjnXm@zn.tnic/
Yikes, will check. Also realized that my > PAGE_SIZE 16k result is
invalid as it should iterate with min(left, PAGE_SIZE). But that just
changes it from 71.2GB/sec to 68.9MB/sec, still a substantial win.
Updated diff below.
Was going to test on aarch64 next...
--
Jens Axboe
next prev parent reply other threads:[~2022-05-23 15:55 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-21 0:46 [RFC] what to do with IOCB_DSYNC? Al Viro
2021-06-21 13:59 ` Christoph Hellwig
2021-06-21 14:03 ` Matthew Wilcox
2021-06-21 14:09 ` Christoph Hellwig
2021-06-21 14:16 ` Matthew Wilcox
2021-06-21 14:22 ` Christoph Hellwig
2021-06-21 14:32 ` Al Viro
2021-06-21 14:35 ` Christoph Hellwig
2021-06-21 15:22 ` Jens Axboe
2022-05-21 17:48 ` Al Viro
2022-05-21 19:03 ` Jens Axboe
2022-05-21 22:14 ` Jens Axboe
2022-05-22 7:45 ` Christoph Hellwig
2022-05-22 10:23 ` Matthew Wilcox
2022-05-22 10:36 ` Al Viro
2022-05-22 11:15 ` Matthew Wilcox
2022-05-22 11:45 ` Christoph Hellwig
2022-05-22 12:39 ` Jens Axboe
2022-05-22 12:48 ` Al Viro
2022-05-22 13:02 ` Jens Axboe
2022-05-22 13:07 ` Al Viro
2022-05-22 13:09 ` Jens Axboe
2022-05-22 18:06 ` Jens Axboe
2022-05-22 18:25 ` Al Viro
2022-05-22 18:29 ` Jens Axboe
2022-05-22 18:39 ` Al Viro
2022-05-22 18:48 ` Jens Axboe
2022-05-22 19:04 ` Al Viro
2022-05-22 20:03 ` Jens Axboe
2022-05-23 0:42 ` Al Viro
2022-05-23 1:22 ` Jens Axboe
2022-05-23 1:28 ` Jens Axboe
2022-05-23 1:50 ` Jens Axboe
2022-05-23 2:43 ` Jens Axboe
2022-05-23 14:22 ` Al Viro
2022-05-23 14:34 ` Jens Axboe
2022-05-23 14:47 ` Al Viro
2022-05-23 15:12 ` Jens Axboe
2022-05-23 15:44 ` Jens Axboe
2022-05-23 15:49 ` Matthew Wilcox
2022-05-23 15:55 ` Jens Axboe [this message]
2022-05-23 16:03 ` Jens Axboe
2022-05-26 14:46 ` Jason A. Donenfeld
2022-05-27 10:09 ` Ingo Molnar
2022-05-27 10:15 ` Jason A. Donenfeld
2022-05-27 14:45 ` Samuel Neves
2022-05-27 10:25 ` Ingo Molnar
2022-05-27 10:36 ` Borislav Petkov
2022-05-28 20:54 ` Sedat Dilek
2022-05-28 20:38 ` Sedat Dilek
2022-05-28 20:39 ` Sedat Dilek
2022-05-23 16:15 ` Al Viro
2022-05-25 14:34 ` Matthew Wilcox
2022-05-26 23:19 ` Al Viro
2022-05-27 14:51 ` Jens Axboe
2022-05-22 12:21 ` Al Viro
2022-05-22 7:43 ` Christoph Hellwig
2022-05-22 12:41 ` Al Viro
2022-05-22 12:51 ` Christoph Hellwig
2021-06-21 14:22 ` Al Viro
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