[frameworks-solid] [Bug 398908] Dolphin uses up huge amounts of memory over time

[Alexander Meshcheryakov]

https://bugs.kde.org/show_bug.cgi?id=398908

--- Comment #119 from Alexander Meshcheryakov <alexander.s.m at gmail.com> ---
I have noticed that memory leaks are happening not gradually but in sharp
spikes. During such spikes Dolphin consumes about 70% of a single CPU core. I
have not figured out the trigger of such moments. Sometimes leaks happen even
while user session is locked, and as far as I can tell there are no updates in
content of directories which Dolphin displays. But it seems leaks happen more
often when I interact with my PC.

The patch from #c116 does not remove these CPU usage spikes. But with patched
solid instead of leaking ~200 MB at a time, Dolphin leaks just 5-20 MB.

Here is some data:
Obligatory heaptrack of Dolphin running for 3 days with solid patched from
#c116
http://45.86.162.4/files/2022/heaptrack.dolphin.solid_patch_116.19.zst

CPU and RSS consumption graphs for Dolphin with patched solid
http://45.86.162.4/images/2022/dolphin_patched_solid_cpu.png
http://45.86.162.4/images/2022/dolphin_patched_solid_rss.png

Here are the graphs for Dolphin with unpatched solid
http://45.86.162.4/images/2022/dolphin_cpu_2.png
http://45.86.162.4/images/2022/dolphin_rss_2.png

Note how memory leaks are simultaneous with CPU spikes.

>From all these observations I am rather confident that the core issue is not an
inefficiency of StorageAccess::clearTextPath which is fixed by Méven Car patch,
but rather mysterious spurious ~2 min intensive process related to KDirWatch. I
suppose this process does not do anything useful and should be
disabled/optimized.

Also this process seems to be related to filesystem tags (user.xdg.tags in
xattrs). If I remove /home/self/.local/share/user-places.xbel at the moment it
gets populated with tags:/ again Dolphin leaks.

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