From: Jens Axboe <[email protected]>
To: Olivier Langlois <[email protected]>,
Pavel Begunkov <[email protected]>,
[email protected], [email protected]
Subject: Re: [PATCH v4] io_uring: reduce latency by reissueing the operation
Date: Thu, 24 Jun 2021 18:45:21 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <9e8441419bb1b8f3c3fcc607b2713efecdef2136.1624364038.git.olivier@trillion01.com>
On 6/22/21 6:17 AM, Olivier Langlois wrote:
> It is quite frequent that when an operation fails and returns EAGAIN,
> the data becomes available between that failure and the call to
> vfs_poll() done by io_arm_poll_handler().
>
> Detecting the situation and reissuing the operation is much faster
> than going ahead and push the operation to the io-wq.
>
> Performance improvement testing has been performed with:
> Single thread, 1 TCP connection receiving a 5 Mbps stream, no sqpoll.
>
> 4 measurements have been taken:
> 1. The time it takes to process a read request when data is already available
> 2. The time it takes to process by calling twice io_issue_sqe() after vfs_poll() indicated that data was available
> 3. The time it takes to execute io_queue_async_work()
> 4. The time it takes to complete a read request asynchronously
>
> 2.25% of all the read operations did use the new path.
>
> ready data (baseline)
> avg 3657.94182918628
> min 580
> max 20098
> stddev 1213.15975908162
>
> reissue completion
> average 7882.67567567568
> min 2316
> max 28811
> stddev 1982.79172973284
>
> insert io-wq time
> average 8983.82276995305
> min 3324
> max 87816
> stddev 2551.60056552038
>
> async time completion
> average 24670.4758861127
> min 10758
> max 102612
> stddev 3483.92416873804
>
> Conclusion:
> On average reissuing the sqe with the patch code is 1.1uSec faster and
> in the worse case scenario 59uSec faster than placing the request on
> io-wq
>
> On average completion time by reissuing the sqe with the patch code is
> 16.79uSec faster and in the worse case scenario 73.8uSec faster than
> async completion.
Thanks for respinning with a (much) better commit message. Applied.
--
Jens Axboe
next prev parent reply other threads:[~2021-06-25 0:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-22 12:17 [PATCH v4] io_uring: reduce latency by reissueing the operation Olivier Langlois
2021-06-22 17:54 ` Pavel Begunkov
2021-06-22 18:01 ` Pavel Begunkov
2021-06-22 19:05 ` Olivier Langlois
2021-06-22 20:51 ` Pavel Begunkov
2021-06-22 20:52 ` Pavel Begunkov
2021-06-25 0:45 ` Jens Axboe [this message]
2021-06-25 8:15 ` David Laight
2021-06-28 6:42 ` Olivier Langlois
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox