Re: Bad desktop performance with Linux 5.8
On 11/15/20 12:05 AM, Kévin Le Gouguec wrote:
> Hello,
>
> I am running Debian Buster (XFCE) on a Dell Laptop[1] with some packages
> upgraded from backports[2], notably linux-image-amd64. After upgrading
> to version 5.8, I started noticing some UI "choppiness". To give a few
> examples:
>
> - when typing (in any application, e.g. Emacs, Terminator, Firefox): at
> its worst, I can type a bunch of words, sit back, wait a few seconds,
> then watch the words appear letter by letter.
>
> - when launching programs: startup times are very inconsistent; e.g. if
> I loop on
> while time emacs -Q --eval '(kill-emacs)' ; do continue ; done
> or
> while time terminator -x "bash -c exit" ; do continue ; done
> times vary between 1× and 3× what I observe on kernel 5.7 (where times
> barely vary at all, ±5% at most).
>
> - when scrolling a PDF with Evince with the touchpad: the display
> "freezes" (the pages do not seem to be scrolling) and jumps to the new
> position after a few seconds; nonetheless, the pages *do* scroll
> continuously, as the mouse pointer changes from an arrow to an I-beam,
> presumably as text and whitespace move past it.
>
> Neither htop, journalctl nor dmesg report anything suspicious to my
> untrained eye; the only difference I spotted was the CPU governor: on
> 5.7 it is "powersave"; on 5.8 it is "ondemand". Naively cpufreq-setting
> all cores to powersave on 5.8 does not make the problem go away, though.
>
> One curious thing is that looking at
> watch -n0.5 grep MHz /proc/cpuinfo
>
> - on 5.7, the system is very responsive, and the idle frequency is
> around 800 MHz;
> - on 5.8, the system lags despite the idle frequency never going below
> 1700 MHz.
>
> This might all be a red herring though, for all I know. I did not
> immediately realize that the performance drops came from 5.8; I only
> understood that after studying a bunch of other hypotheses (uninstalling
> xserver-xorg-video-intel, disabling services such as speech-dispatcher
> and tor), coming up short, rebooting, opening Grub's "advanced options"
> and realizing that 5.7 was still on my system.
>
> I've since rebooted multiple times on 5.7 and 5.8, and I'm positive that
> the problem only occurs with 5.8.
>
>
> I'm not sure what to look at next. I've searched the Web for people
> having performance issues with 5.8, but nothing caught my eye.
>
> I realize that "performance bad ☹" testimonies like this are probably
> not very actionable; let me know if there's anything I can do to make
> this "diagnosis" more precise. Also, I hope this is the right place for
> this kind of support request; I assume it is too vague as-is for a
> proper bug report… Let me know if I should post this elsewhere.
>
>
> Thank you for your time, and sorry for the poor report.
>
>
> [1] Dell Latitude 3190. Attached outputs from lscpu and lspci:
>
>
>
> [2] Potentially relevant backport packages:
>
> $ aptitude search '?narrow(?installed, ?archive(buster-backports)) ?name(firmware~|linux~|wireless)' -F '%p'
> firmware-amd-graphics
> firmware-iwlwifi
> firmware-linux
> firmware-linux-nonfree
> firmware-misc-nonfree
> linux-image-5.8.0-0.bpo.2-amd64
> linux-image-amd64
> wireless-regdb
>
> Potentially relevant non-free packages:
>
> $ aptitude search '?installed ?section(non-free/) !?name(-doc$~|^manpages-)' -F '%p'
> amd64-microcode
> firmware-amd-graphics
> firmware-iwlwifi
> firmware-linux
> firmware-linux-nonfree
> firmware-misc-nonfree
> intel-microcode
>
Hi Kévin,
Linux kernel version (5.8) is old and unsupported (EOL) branch. Maybe
you should wait for 5.9 to be available from backports or even 5.10 -
this version will be LTS and next Debian stable version will probably
use it. While waiting you can try to use 5.7 if possible.
Kind regards
Georgi
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