linux-kernel - Re: niced tasks on SMT system

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Date:   Fri, 29 Dec 2017 00:07:50 +0300
From:   Ozgur <ozgur@...sey.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Mike Galbraith <efault@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        kernel list <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>
Subject: Re: niced tasks on SMT system



28.12.2017, 23:59, "Pavel Machek" <pavel@....cz>:
> Hi!
>
>>  >>  > Ok, so I'm compiling, and I'd like to run a flight simulator.
>>  >>  >
>>  >>  > Flightgear normally does 20fps on my system... kinda low but playable.
>>  >>  >
>>  >>  > I have reniced make -j 5 fo kernel running. Scheduler gives 100% of
>>  >>  > one of CPUs to Flightgear (good), but the smt sibling is used by the
>>  >>  > compilation, and I'm down to 9 fps. Not good.
>>  >>  >
>>  >>  > Even with single-threaded make, I have 10-13fps.
>>  >>  >
>>  >>  > Is there way to learn which CPUs are SMT siblings?
>>  >>
>>  >>  cat /sys/devices/system/cpu/cpu{N}/topology/thread_siblings
>>  >
>>  > Thanks for a hint.
>>  >
>>  > Well, something is definitely wrong there:
>>  >
>>  > pavel@duo:/data/l/linux-n900$ cat
>>  > /sys/devices/system/cpu/cpu0/topology/thread_siblings
>>  > 03
>>
>>  Ops,
>>
>>  do you fly on N900 via flightgear? :)
>>  I have two N900 and one run gentoo.
>
> No, no flightgear on N900. It was preparing kernels for my N900 that
> interfered with flying.

I would like to be involved in the team and share the job. firstly I will read the project documents.

> BTW there's lot of fun to be had with
> N900. https://wiki.postmarketos.org/wiki/Nokia_N900_(nokia-rx51) I
> even have voice calls working on Debian, help welcome :-).

I use default Maemo, the n900 is already debian, gentoo run a chroot :)

>                                                                         Pavel

Ozgur

> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html