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Seemingly random performance degradation in 4.13

From vcaputo@pengaru.com
Newsgroups linux.kernel
Subject Seemingly random performance degradation in 4.13
Date 2017-09-13 06:40 +0200
Message-ID <up7CW-2z5-7@gated-at.bofh.it> (permalink)
Organization linux.* mail to news gateway

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Hello,

I've been working on some graphics hacks which has me paying close
attention to frame rates.  Something I've noticed recently in the 4.13
cycle is a seemingly random loss of ~40% frame rate.  These are purely
software-rendered hacks, and I haven't spent much time trying to figure out
what is changing when the performance drops - typically the performance is
restored on a subsequent boot.

There's been talk of NUMA and scheduler related performance regressions,
and I'm wondering if that's related to what I'm observing.

Is there a fix floating around I can apply and see if it prevents
regressions from occurring?

FYI the machine in question is a 1.8Ghz core2 duo thinkpad x61s, currently
on 4.13-rc7.

If there's anything in particular that would be useful for me to capture
when running one of these tests, a specific perf incantation for example,
I'm happy to test and report the results.

Cheers,
Vito Caputo

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Seemingly random performance degradation in 4.13 vcaputo@pengaru.com - 2017-09-13 06:40 +0200

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