linux-kernel - niced tasks on SMT system

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Message-ID: <20171228121024.GA18152@amd>
Date:   Thu, 28 Dec 2017 13:10:25 +0100
From:   Pavel Machek <pavel@....cz>
To:     Thomas Gleixner <tglx@...utronix.de>,
        kernel list <linux-kernel@...r.kernel.org>
Cc:     mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        peterz@...radead.org
Subject: niced tasks on SMT system

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?

Is there way to disable SMT during runtime?

Can I do something to improve Flightgear performance and still do
compilation?

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

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