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?
next prev parent 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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