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From: Al Viro <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Pavel Begunkov <[email protected]>,
	yangerkun <[email protected]>,
	[email protected], [email protected],
	[email protected]
Subject: Re: [PATCH] block: reexpand iov_iter after read/write
Date: Thu, 6 May 2021 18:55:09 +0000	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Thu, May 06, 2021 at 11:19:03AM -0600, Jens Axboe wrote:

> Doing a quick profile, on the latter run with ->write_iter() we're
> spending 8% of the time in _copy_from_iter(), and 4% in
> new_sync_write(). That's obviously not there at all for the first case.
> Both have about 4% in eventfd_write(). Non-iter case spends 1% in
> copy_from_user().
> 
> Finally with your branch pulled in as well, iow using ->write_iter() for
> eventfd and your iov changes:
> 
> Executed in  485.26 millis    fish           external
>    usr time  103.09 millis   70.00 micros  103.03 millis
>    sys time  382.18 millis   83.00 micros  382.09 millis
> 
> Executed in  485.16 millis    fish           external
>    usr time  104.07 millis   69.00 micros  104.00 millis
>    sys time  381.09 millis   94.00 micros  381.00 millis
> 
> and there's no real difference there. We're spending less time in
> _copy_from_iter() (8% -> 6%) and less time in new_sync_write(), but
> doesn't seem to manifest itself in reduced runtime.

Interesting... do you have instruction-level profiles for _copy_from_iter()
and new_sync_write() on the last of those trees?

  reply	other threads:[~2021-05-06 18:55 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01  7:18 [PATCH] block: reexpand iov_iter after read/write yangerkun
2021-04-06  1:28 ` yangerkun
2021-04-06 11:04   ` Pavel Begunkov
2021-04-07 14:16     ` yangerkun
2021-04-09 14:49 ` Pavel Begunkov
2021-04-15 17:37   ` Pavel Begunkov
2021-04-15 17:39     ` Pavel Begunkov
2021-04-28  6:16       ` yangerkun
2021-04-30 12:57         ` Pavel Begunkov
2021-04-30 14:35           ` Al Viro
2021-05-06 16:57             ` Pavel Begunkov
2021-05-06 17:17               ` Al Viro
2021-05-06 17:19             ` Jens Axboe
2021-05-06 18:55               ` Al Viro [this message]
2021-05-06 19:15                 ` Jens Axboe
2021-05-06 21:08                   ` Al Viro
2021-05-06 21:17                     ` Matthew Wilcox
2021-05-07 14:59                     ` Jens Axboe

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