https://bugs.kde.org/show_bug.cgi?id=488205
Bug ID: 488205
Summary: kwin_wayland - high CPU load when requesting clipboard
content (using wl-paste) + weird strace (many readlink
calls on
"/home/<username>/<some_random_executable_name>)"
Classification: Plasma
Product: kwin
Version: 6.0.5
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: general
Assignee: kwin-bugs-n...@kde.org
Reporter: f...@fedy.cz
Target Milestone: ---
Created attachment 170268
--> https://bugs.kde.org/attachment.cgi?id=170268&action=edit
strace - high cpu
SUMMARY
Recently I noticed that sometimes kwin_wayland eats a significant portion of my
CPU. Normally it sits at around 2.5% (in top) but in those situation it might
go up to 45%. Finally I was able to narrow it down to the use of some bash
scripts that monitor and process the clipboard. Once terminated, the
kwin_wayland CPU use goes down to normal.
I use wl-paste in those scripts. The simplest one to reproduce would be
something like (tested):
#!/bin/bash
while true; do
sleep 0.1s
clip=$(wl-paste -n -t text 2> /dev/null)
done;
Once run the kwin_waylands CPU use increases to about 25% (NOTE: this system is
a measly J5005, might be much less on a modern system).
STEPS TO REPRODUCE
1. run top to monitor the kwin_wayland
1. run the bash script above (or similar)
2. in top - observe increased cpu use
3. run strace on the kwin_wayland process ( strace -p <pid> -i ) and observe
the weirdness
4. use strace to get stack trace on those readlink calls:
strace -p <pid> -k --stack-trace-frame-limit=16 -e readlink --syscall-limit=100
5. and (probably) related getcwd calls:
strace -p <pid> -k --stack-trace-frame-limit=16 -e getcwd --syscall-limit=100
OBSERVED RESULT
1. kwin_wayland cpu use goes way up
2. We start getting a very weird strace listing with entries like:
[00007fe30811dd5b] readlink("/usr", 0x7ffc3483a350, 1023) = -1 EINVAL
(Nepřípustný argument)
[00007fe30811dd5b] readlink("/usr/bin", 0x7ffc3483a350, 1023) = -1 EINVAL
(Nepřípustný argument)
[00007fe30811dd5b] readlink("/usr/bin/syncthing", 0x7ffc3483a350, 1023) = -1
EINVAL (Nepřípustný argument)
[00007fe30811c6cb] getcwd("/home/usrnm", 1024) = 12
[00007fe30811dd5b]
readlink("/home/usrnm/lsp-plugins-para-equalizer-x16-stereo", 0x7ffc3483a350,
1023) = -1 ENOENT (Adresář nebo soubor neexistuje)
[00007fe30811c6cb] getcwd("/home/usrnm", 1024) = 12
[00007fe30811dd5b] readlink("/home/usrnm/gnome-control-center", 0x7ffc3483a350,
1023) = -1 ENOENT (Adresář nebo soubor neexistuje)
[00007fe30811c6cb] getcwd("/home/usrnm", 1024) = 12
[00007fe30811dd5b] readlink("/home/usrnm/qdirstat", 0x7ffc3483a350, 1023) = -1
ENOENT (Adresář nebo soubor neexistuje)
[00007fe30811c6cb] getcwd("/home/usrnm", 1024) = 12
[00007fe30811dd5b] readlink("/home/usrnm/qvidcap", 0x7ffc3483a350, 1023) = -1
ENOENT (Adresář nebo soubor neexistuje)
... and many many more
[ more in strace-high_cpu.txt ]
3. This raises many many questions,like :
- Why does the kwin_wayland seem to be enumerating all the executables on my
system?
- Why does it trying to locate them (symlinked) in the base of my home
directory (which is not even in the $PATH)?
4. Stack trace of the readlink calls might point us in the general direction:
readlink("/usr/bin", 0x7ffc3483a350, 1023) = -1 EINVAL (Nepřípustný argument)
> /usr/lib64/libc.so.6(readlink+0xb) [0x10ad5b]
> /usr/lib64/libc.so.6(realpath@@GLIBC_2.3+0x3b7) [0x41df7]
>
/usr/lib64/libQt6Core.so.6.7.1(QFileSystemEngine::canonicalName(QFileSystemEntry
const&, QFileSystemMetaData&)+0x94) [0x345314]
>
/usr/lib64/libQt6Core.so.6.7.1(QFileInfoPrivate::getFileName(QAbstractFileEngine::FileName)
const+0x1fa) [0x14a43a]
> /usr/lib64/libQt6Core.so.6.7.1(QFileInfo::canonicalFilePath() const+0xac)
[0x14b83c]
> /usr/lib64/libkwin.so.6.0.5(std::_Function_handler<bool
(QExplicitlySharedDataPointer<KService> const&),
KWin::fetchProcessServiceField(QString const&, QString
const&)::{lambda(QExplicitlySharedDataPointer<KService>
const&)#1}>::_M_invoke(std::_Any_data const&,
QExplicitlySharedDataPointer<KService> const&)+0x114) [0x387eb4]
>
/usr/lib64/libKF6Service.so.6.2.0(applyFilter(QList<QExplicitlySharedDataPointer<KService>
>&, std::function<bool (QExplicitlySharedDataPointer<KService> const&)>,
bool)+0x113) [0x18c73]
>
/usr/lib64/libKF6Service.so.6.2.0(KApplicationTrader::query(std::function<bool
(QExplicitlySharedDataPointer<KService> const&)>)+0x97) [0x1c847]
>
/usr/lib64/libkwin.so.6.0.5(KWin::KWinDisplay::allowInterface(KWin::ClientConnection*,
QByteArray const&)+0x654) [0x38ab34]
>
/usr/lib64/libkwin.so.6.0.5(KWin::FilteredDisplayPrivate::globalFilterCallback(wl_client
const*, wl_global const*, void*)+0x64) [0x4aa7f4]
> /usr/lib64/libwayland-server.so.0.22.0(display_get_registry+0x9c) [0xbcbc]
> /usr/lib64/libffi.so.8.1.2(ffi_call_unix64+0x55) [0x9055]
> /usr/lib64/libffi.so.8.1.2(ffi_call_int.lto_priv.0+0x1ef) [0x569f]
> /usr/lib64/libffi.so.8.1.2(ffi_call+0x12d) [0x84ed]
> /usr/lib64/libwayland-server.so.0.22.0(wl_closure_invoke.constprop.0+0x172)
[0x67e2]
> /usr/lib64/libwayland-server.so.0.22.0(wl_client_connection_data+0xd1f)
[0xb07f]
> too many stack frames
readlink("/usr/bin/syncthing", 0x7ffc3483a350, 1023) = -1 EINVAL (Nepřípustný
argument)
> /usr/lib64/libc.so.6(readlink+0xb) [0x10ad5b]
> /usr/lib64/libc.so.6(realpath@@GLIBC_2.3+0x3b7) [0x41df7]
>
/usr/lib64/libQt6Core.so.6.7.1(QFileSystemEngine::canonicalName(QFileSystemEntry
const&, QFileSystemMetaData&)+0x94) [0x345314]
>
/usr/lib64/libQt6Core.so.6.7.1(QFileInfoPrivate::getFileName(QAbstractFileEngine::FileName)
const+0x1fa) [0x14a43a]
> /usr/lib64/libQt6Core.so.6.7.1(QFileInfo::canonicalFilePath() const+0xac)
[0x14b83c]
> /usr/lib64/libkwin.so.6.0.5(std::_Function_handler<bool
(QExplicitlySharedDataPointer<KService> const&),
KWin::fetchProcessServiceField(QString const&, QString
const&)::{lambda(QExplicitlySharedDataPointer<KService>
const&)#1}>::_M_invoke(std::_Any_data const&,
QExplicitlySharedDataPointer<KService> const&)+0x114) [0x387eb4]
>
/usr/lib64/libKF6Service.so.6.2.0(applyFilter(QList<QExplicitlySharedDataPointer<KService>
>&, std::function<bool (QExplicitlySharedDataPointer<KService> const&)>,
bool)+0x113) [0x18c73]
>
/usr/lib64/libKF6Service.so.6.2.0(KApplicationTrader::query(std::function<bool
(QExplicitlySharedDataPointer<KService> const&)>)+0x97) [0x1c847]
>
/usr/lib64/libkwin.so.6.0.5(KWin::KWinDisplay::allowInterface(KWin::ClientConnection*,
QByteArray const&)+0x654) [0x38ab34]
>
/usr/lib64/libkwin.so.6.0.5(KWin::FilteredDisplayPrivate::globalFilterCallback(wl_client
const*, wl_global const*, void*)+0x64) [0x4aa7f4]
> /usr/lib64/libwayland-server.so.0.22.0(display_get_registry+0x9c) [0xbcbc]
> /usr/lib64/libffi.so.8.1.2(ffi_call_unix64+0x55) [0x9055]
> /usr/lib64/libffi.so.8.1.2(ffi_call_int.lto_priv.0+0x1ef) [0x569f]
> /usr/lib64/libffi.so.8.1.2(ffi_call+0x12d) [0x84ed]
> /usr/lib64/libwayland-server.so.0.22.0(wl_closure_invoke.constprop.0+0x172)
[0x67e2]
> /usr/lib64/libwayland-server.so.0.22.0(wl_client_connection_data+0xd1f)
[0xb07f]
> too many stack frames
readlink("/home/usrnm/lsp-plugins-para-equalizer-x16-stereo", 0x7ffc3483a350,
1023) = -1 ENOENT (Adresář nebo soubor neexistuje)
> /usr/lib64/libc.so.6(readlink+0xb) [0x10ad5b]
> /usr/lib64/libc.so.6(realpath@@GLIBC_2.3+0x3b7) [0x41df7]
>
/usr/lib64/libQt6Core.so.6.7.1(QFileSystemEngine::canonicalName(QFileSystemEntry
const&, QFileSystemMetaData&)+0x94) [0x345314]
>
/usr/lib64/libQt6Core.so.6.7.1(QFileInfoPrivate::getFileName(QAbstractFileEngine::FileName)
const+0x1fa) [0x14a43a]
> /usr/lib64/libQt6Core.so.6.7.1(QFileInfo::canonicalFilePath() const+0xac)
[0x14b83c]
> /usr/lib64/libkwin.so.6.0.5(std::_Function_handler<bool
(QExplicitlySharedDataPointer<KService> const&),
KWin::fetchProcessServiceField(QString const&, QString
const&)::{lambda(QExplicitlySharedDataPointer<KService>
const&)#1}>::_M_invoke(std::_Any_data const&,
QExplicitlySharedDataPointer<KService> const&)+0x114) [0x387eb4]
>
/usr/lib64/libKF6Service.so.6.2.0(applyFilter(QList<QExplicitlySharedDataPointer<KService>
>&, std::function<bool (QExplicitlySharedDataPointer<KService> const&)>,
bool)+0x17b) [0x18cdb]
>
/usr/lib64/libKF6Service.so.6.2.0(KApplicationTrader::query(std::function<bool
(QExplicitlySharedDataPointer<KService> const&)>)+0x97) [0x1c847]
>
/usr/lib64/libkwin.so.6.0.5(KWin::KWinDisplay::allowInterface(KWin::ClientConnection*,
QByteArray const&)+0x654) [0x38ab34]
>
/usr/lib64/libkwin.so.6.0.5(KWin::FilteredDisplayPrivate::globalFilterCallback(wl_client
const*, wl_global const*, void*)+0x64) [0x4aa7f4]
> /usr/lib64/libwayland-server.so.0.22.0(display_get_registry+0x9c) [0xbcbc]
> /usr/lib64/libffi.so.8.1.2(ffi_call_unix64+0x55) [0x9055]
> /usr/lib64/libffi.so.8.1.2(ffi_call_int.lto_priv.0+0x1ef) [0x569f]
> /usr/lib64/libffi.so.8.1.2(ffi_call+0x12d) [0x84ed]
> /usr/lib64/libwayland-server.so.0.22.0(wl_closure_invoke.constprop.0+0x172)
[0x67e2]
> /usr/lib64/libwayland-server.so.0.22.0(wl_client_connection_data+0xd1f)
[0xb07f]
> too many stack frames
EXPECTED RESULT
1. Accessing (wayland) clipboard should be a relatively cheap operation (in
terms of CPU use).
2. Enumerating the binaries - is that really necessary? Even if so, something
seems to be broken there (the readlink calls point to a weird location in the
home dir).
NOTE: wl-paste has no GUI, maybe that might be triggering the issue?
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 40
KDE Plasma Version: 6.0.5
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.1
ADDITIONAL INFORMATION
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