Originally posted by Michael
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Linux 5.5 Seeing Some Wild Swings In Performance - Improvements But Also Regressions
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perpetually high aufkrawall
acpi-cpufreq really seems to have two advantages over intel_pstate & intel-cpufreq:
1.
It doesn't rely on the Intel idle driver while still being able to put the CPU into its deepest sleep state. (C6 in my case -
i5-3350P [IvyBridge])
This You can easily check with:
Code:sudo cpupower monitor
It isn't misleading as opposed to Intel's performance governor:
acpi-cpufreq's performance setting always requests the highest frequency from the CPU (usually the boost state), whereas Intel's very own driver still dynamically scales the frequency, which also leads to increased latency.
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Wow. Epic swings. That is just rubbish. Performance regression on directory basis?
How hard can it be? Run on a farm. Compile on every commit, build against a few targets, vote for a suite, run it and dump a feedback on the developer of the commit. Priority to specific directories in the kernel. arch/*, block, kernel, mm, fs.Last edited by milkylainen; 01 December 2019, 06:29 PM.
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Originally posted by Michael View Post
Right some tests are ~50% faster, others ~50% slower. I am working on bisecting the biggest ones right now.
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Originally posted by birdie View Post
Erm, what about making kernel 5.4 performance a baseline (100%) and showing 5.5 gains/losses vs. the old kernel? That would be a lot less confusing.Michael Larabel
https://www.michaellarabel.com/
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Originally posted by Alliancemd View Post
I find it interesting(was not pointed out) that on Intel "Memcached mcperf" sees a big regression while on AMD it sees a big performance boost.Michael Larabel
https://www.michaellarabel.com/
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Originally posted by milkylainen View PostWow. Epic swings. That is just rubbish. Performance regression on directory basis?
How hard can it be? Run on a farm. Compile on every commit, build against a few targets, vote for a suite, run it and dump a feedback on the developer of the commit. Priority to specific directories in the kernel. arch/*, block, kernel, mm, fs.
Actually this robot reports a lot of various regressions along with git commits which caused them.
Kudos to Intel for doing that. The company really does great things for Linux (and as far as I know they extensively use Linux for developing new CPU architectures).
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Originally posted by Linuxxx View Post
I know how You feel...
However, we as Intel victims are not completely helpless:
Recently, I have found out why passingCode:intel_pstate=disable
From the RedHat Low-Latency tuning guide:
So all along it was Intel's IDLE driver that was the culprit, not the P-State driver!
This finally explains why Intel systems always felt so sluggish, even though I was always using the Performance governor while also setting the so-called Perf-Bias to zero for maximum performance-bias!
Seriously Intel, are you doing this on purpose?
powersave does nothing to save power, and performance does nothing to help with performance!
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