On Wed, Feb 3, 2021 at 5:54 PM Michael Catanzaro <mcatanzaro@gnome.org> wrote:
Hi,

Has anybody investigated Jim Salter's claims that Fedora 32 is slow to
launch applications? Recent article:

https://arstechnica.com/gadgets/2021/02/ubuntu-core-20-adds-secure-boot-with-hardware-backed-encryption/

"in my experience, Fedora 32 is noticeably, demonstrably more sluggish
to launch applications than Ubuntu is in general."

Original article:

https://arstechnica.com/gadgets/2020/05/linux-distro-review-fedora-workstation-32/

Would be good to know, for starters, whether this difference is real
and measurable.
This was bugging me for a while. I also noticed that Fedora 32 is a bit slower than it used to be. Compilation time of a project that I'm working on went from ~35-36 seconds to ~47-48. At first I thought that it's just another round of CPU vulnerabilities mitigations that introduced a performance drop. But after some digging I found that the default CPU governor was switched from 'ondemand' to 'schedutil' in Fedora kernel 5.9.7:
https://src.fedoraproject.org/rpms/kernel/c/73c86ebaee23df8310b903c1dab2176d443f5a3a?branch=rawhide
(see configs/fedora/generic/CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL)

I switched it back using cpupower from kernel-tools:
$ sudo cpupower frequency-set --governor ondemand

And confirmed that my compilation time went back to the previous ~35 seconds.
In the end I switched the governor to 'performance' and shaved another 5 seconds. And gnome-shell no longer feels sluggish, switching tabs in the browser is also instant.
To make the change permanent I used settings in /etc/sysconfig/cpupower and enabled cpupower service:
$ sudo systemctl enable --now cpupower.service

The change of the default CPU governor looks pretty significant to me, but I couldn't find any discussions about it. 


Michael

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--
Viktor