Comment 43 for bug 109943

hi guys.
i also experienced the issue, but i think i found the reason. in my case, the cpu usage is dependent on the gtk theme.
when switching the gtk theme to Clearlooks using:
$ gtk-theme-switch2 /usr/share/themes/Clearlooks
the cpu usage of X immediately jumps to 100%. but when switching to a different theme, e.g.:
$ gtk-theme-switch2 /usr/share/themes/Adwaita
with progress bar in status bar still active, the cpu usage immediately drops ~9% (still not 0% though) and thunderbird is way more responsive then.
imho, this looks like the issue is either inside the theme code itself or gtk code the themes are using.
hope this helps.