https://bugs.kde.org/show_bug.cgi?id=370003
Bug ID: 370003
Summary: Performance issues (laggy animations, stuttering
keyboard input handling, severe frame drops in videos)
after using plasmashell for a few days
Product: plasmashell
Version: 5.7.5
Platform: Archlinux Packages
OS: Linux
Status: UNCONFIRMED
Severity: normal
Priority: NOR
Component: general
Assignee: k...@davidedmundson.co.uk
Reporter: r...@robwu.nl
CC: bhus...@gmail.com, plasma-b...@kde.org
Created attachment 101421
--> https://bugs.kde.org/attachment.cgi?id=101421&action=edit
perf record -e cpu-clock -p `pidof plasmashell` -o perf2.data # switch between
desktops a couple of times and ^C
For many months I have experienced performance issues:
- Obvious animation lags, e.g. switching between desktops, or hiding/restoring
windows
- Keyboard input handling seems to stutter, e.g. typing in the terminal or
browser is not smooth: If I hold a key pressed, instead of showing a steady
stream of characters, the input seems to stutter.
- Videos are shown with multiple framedrops every few seconds, e.g. in VLC or
in YouTube/Facebook videos in Chromium.
Although I don't know how to reproduce the issue, it is not a question of
whether the performance issues occur, but when (maybe after a few hours of
use?).
The issue is really caused by plasmashell, if I stop plasmashell the
performance issues disappear, when I resume plasmashell the issues return:
$ pkill -SIGSTOP plasmashell # perf issues gone, and plasmashell is obviously
unusable (frozen/stopped).
$ pkill -SIGCONT plasmashell # perf issues back
The work-around to restart plasmashell, but doing so reorders the task items so
it is not free of side effects.
$ kquitapp5 plasmashell && kstart5 plasmashell
---
ADDITIONAL INFORMATION
After about a week of usage (with a few suspend/resume in between, some web
browsing and using the terminal), I saw the issue again. I used "ps -o pcpu -C
plasmashell" to get the CPU usage and saw the reported CPU drop from 28.8 to
2.2 after restarting plasmashell. After taking two more measures after an hour
and another few hours the numbers slowly climbed to 2.5, then 3.8%.
Then I recorded the CPU usage using perf while switching between desktops (5
times). The result is shown below (and attached). It seems that something in
plasmashell is holding locks excessively often. And also the time spent by
qstrcmp is a bit suspicious.
$ perf record -e cpu-clock -p `pidof plasmashell` -o perf2.data
$ perf report -i perf2.data
Samples: 19K of event 'cpu-clock:u', Event count (approx.): 4926500000
Overhead Command Shared Object Symbol
16.53% plasmashell libpthread-2.24.so [.]
__lll_lock_elision
7.91% plasmashell libpthread-2.24.so [.]
__lll_unlock_elision
7.74% plasmashell libQt5Core.so.5.7.0 [.] qstrcmp
5.80% QXcbEventReader libpthread-2.24.so [.]
__lll_lock_elision
5.31% QXcbEventReader libc-2.24.so [.] malloc
3.96% plasmashell libc-2.24.so [.] _int_free
3.32% plasmashell libQt5Core.so.5.7.0 [.]
QAbstractEventDispatcher::filterNativeEvent
3.27% plasmashell libc-2.24.so [.] malloc
2.77% QXcbEventReader libc-2.24.so [.] _int_malloc
2.53% plasmashell libc-2.24.so [.]
malloc_consolidate
2.51% QXcbEventReader libc-2.24.so [.]
__memmove_avx_unaligned_erms
2.34% plasmashell libc-2.24.so [.] _int_malloc
1.75% plasmashell libQt5Core.so.5.7.0 [.] QMutex::lock
1.38% plasmashell libQt5Core.so.5.7.0 [.]
QMutex::unlock
1.33% plasmashell libQt5XcbQpa.so.5.7.0 [.]
QXcbConnection::processXcbEvents
1.32% QXcbEventReader libpthread-2.24.so [.]
__lll_unlock_elision
1.26% QXcbEventReader libpthread-2.24.so [.]
pthread_cond_signal@@GLIBC_2.3.2
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