Slow start because of extensive file scanning

Submitted by bluebell on
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qtractor

Since I began compiling Qtractor with qt6 I noticed longer start times of Qtractor. Especially on an old Core i5 it takes now 6 seconds until Qtractor is usable. Strace showed that Qtractor (or qt6) scans a lot of dirs, not only in the home directory but also in /usr and /var. It even opens dot-files like .vimrc, makes 1176 stat-calls to /etc/localtime and searches e.g. 2105 times for each icon in many directories including /var/lib/snapd. Having network mounts or links to them in the home dir slows down the process even more.

Opening View -> Options -> Display -> Icons theme to select a directory for icons is affected, too.

Custom\IconsTheme is set but scanned after all other dirs are scanned.

Is it possible to avoid the scanning of other directories if Custom\IconsTheme is set?

Submitted by rncbc on Sun, 18 May 2025 - 09:58

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that, is, quite, strange... can't figure out what's causing that behavior, as I never seen such a trouble...

backup and try with a blank slate configuration file, and if it doesn't behave like so right from the start, try one step a time, changing options to your former preferences, one by one, and find what's causing trouble...

good luck :)
byee

Submitted by bluebell on Sun, 18 May 2025 - 12:02

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It happened with a deleted Qtractor.conf, too. I did some research and found out that QT6 uses $XDG_DATA_DIRS as the default search path for icons. On my machine it was set to /usr/share/xubuntu:/usr/share/xfce4:/usr/local/share:/usr/share:/var/lib/snapd/desktop:/usr/share

Setting it to $HOME/qtractor/themes where I have my icon set for Qtractor makes Qtractor start fast again.

EDIT: have to set it to /usr/share else CALF plugins will crash Qtractor when opening their GUI.

Submitted by rncbc on Mon, 19 May 2025 - 06:58

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there's nothing wrong with that, I suppose all recent desktops envs have XDG_DATA_DIRS set to similar string (here in plasma6 it's $HOME/.local/share/flatpak/exports/share:/var/lib/flatpak/exports/share:/usr/local/share:/usr/share but it may vary for instance whether you ever had that flatpak stuff installed previously...)

I guess in your particular case one of those paths is network mounted, perhaps?

my home directory was also scanned and there are links to NFS-shares.

However, stripping XDG_DATA_DIRS speeds up Qtractor's starts on my system.

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