lkml.org 
[lkml]   [2022]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v1] io_uring: Add support for napi_busy_poll
From
On 2/20/22 11:37 AM, Olivier Langlois wrote:
> On Sat, 2022-02-19 at 17:22 -0700, Jens Axboe wrote:
>>
>> Outside of this, I was hoping to see some performance numbers in the
>> main patch. Sounds like you have them, can you share?
>>
> Yes.
>
> It is not much. Only numbers from my application and it is far from
> being the best benchmark because the result can be influenced by
> multiple external factors.
>
> Beside addressing the race condition remaining inside io_cqring_wait()
> around napi_list for v2 patch, creating a benchmark program that
> isolate the performance of the new feature is on my todo list.
>
> I would think that creating a simple UDP ping-pong setup and measure
> RTT with and without busy_polling should be a good enough test.

Yes, a separate targeted test like that would be very useful and
interesting indeed!

> In the meantime, here are the results that I have:
>
> Without io_uring busy poll:
> reaction time to an update: 17159usec
> reaction time to an update: 19068usec
> reaction time to an update: 23055usec
> reaction time to an update: 16511usec
> reaction time to an update: 17604usec
>
> With io_uring busy poll:
> reaction time to an update: 15782usec
> reaction time to an update: 15337usec
> reaction time to an update: 15379usec
> reaction time to an update: 15275usec
> reaction time to an update: 15107usec

OK, that's a pretty good improvement in both latency and
deviation/consistency. Is this using SQPOLL, or is it using polling off
cqring_wait from the task itself? Also something to consider for the
test benchmark app, should be able to run both (which is usually just
setting the SETUP_SQPOLL flag or not, if done right).

> Concerning my latency issue with busy polling, I have found this that
> might help me:
> https://lwn.net/ml/netdev/20201002222514.1159492-1-weiwan@google.com/
>

--
Jens Axboe

\
 
 \ /
  Last update: 2022-02-20 20:39    [W:1.104 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site