Re: Performance improvement with 6d740fb01b9f0f5ea7a82f4d5e458d91940a19ee

[Lukáš Doktor]

Dne 25. 05. 23 v 17:21 Stefan Hajnoczi napsal(a):
> On Thu, 25 May 2023 at 06:18, Lukáš Doktor <ldoktor@redhat.com> wrote:
>> the perf-ci detected and bisected the 6d740fb - aio-posix: do not nest poll 
>> handlers - as a performance improvement when using multiple concurrent jobs 
>> and 4k (22%) as well as 1024k (63%) blocks on aarch64 (on a slow rotational 
>> disk).
>>
>>     
>> https://ldoktor.github.io/tmp/RedHat-virtlab-arm09/v8.0.0/150-improvement.html
>>
>> Based on the commit message I guess it's expected so take this just as a 
>> record of an improvement.
> 
> The commit was not intended to change performance and I'm not sure why
> it happens!
> 

It had and today the x86_64 pipeline finished which shows similar improvement 
just not in read but rather in write instead and only for 4k blocks (~40%). For 
1024k blocks I can see it scoring a bit better (~1.5%). Reads are too jittery 
to really tell anything on that machine. Anyway I have not done any thorough 
testing, just a bisection with the most significant setting.

From around the same time I can see a NVMe regression in 4k writes, but first 
bisection job showed nothing. I'll increase the range and try again as each job 
since that day shows similar drop.

Regards,
Lukáš

> Thanks for letting me know.
> 
> Stefan
>

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