Re: Patch: fix 100% cpu when mime-info files are updated

[Alexander Larsson <alexl redhat com>]

On Tue, 2003-09-02 at 13:45, Mark McLoughlin wrote:
> Hi,
> 
> On Tue, 2003-09-02 at 10:00, Frederic Crozat wrote:
> > The following patch fixes 100% cpu usage in nautilus (and probably other
> > apps) when mime-info files are modified. To trigger it, simply run
> > "touch /usr/share/mime-info/*" and see nautilus (and maybe your desktop)
> > frozen for a long time :)) This bug has been here since GNOME 2.2 :((
> > 
> > http://qa.mandrakesoft.com/show_bug.cgi?id=2457
> > 
> > Since I'm the patch author, I can't give my r-t approval on it :)
> > 
> > Patch was reviewed by Alex.
> 
> 	I have to say I'm a little worried about a patch like this going in at
> this stage. It looks potentially risky - changing (even slightly) the
> behaviour/semantics of gnome-vfs this close to the release.

The only user of this I found in my tree is gnome-settings-daemon and
nautilus. Both users want this fix and seem safe with the change.

> 	Also, I don't really understand why this fixes the bug and why we're
> adding the timeout to gnome-vfs rather than Nautilus.

The core problem is that the way things are set up a change of mime data
ends up with a whole bunch of mime db data_changed emissions. Some of
these are from internally in the library, and some from fam change
events for every write of the files. Since nautilus does a fair amount
of work for each mime data change doing this work many times is really
expensive. The patch just delays emission for a short while so the
change events can be combined into just one.

The initial patch frederic wrote was for nautilus, but that patch had a
much higher complexity due to the fact that nautilus uses this signal in
several places and for several objects which lead to memory management
issues. Putting the fix in gnome-vfs makes it much cleaner, plus it
fixes the problem for all applications using gnome-vfs.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
                   alexl redhat com    alla lysator liu se 
He's an uncontrollable zombie librarian on the edge. She's a mentally unstable 
mutant bodyguard with a knack for trouble. They fight crime!