KConfig/KLockFile performance (was KMimeType performance)

[David Faure]

On Wednesday 10 October 2007, Thomas Braxton wrote:
> On 10/9/07, Nhuh Put <nhuh.put at web.de> wrote:
> >
> > Von: Thomas Braxton
> > Gesendet: Dienstag, 9. Oktober 2007 21:22
> > An: kde-core-devel at kde.org
> > Betreff: Re: KConfig/KLockFile performance (was KMimeType performance)
> >
> > > On 10/9/07, David Faure <faure at kde.org> wrote:
> > > On Tuesday 09 October 2007, Maksim Orlovich wrote:
> > > > KDesktopFile/KConfig tries to lock the file with KLockFile
> > >
> > > Huh. I thought we got rid of the "bool readonly" because it made no
> > behavior difference,
> > > but if KConfig locks the file then surely we need a "ReadOnly" flag
> > again?
> > > Or better: we should lock at the time of writing to the file, not when
> > just reading from it!
> > >
> > > your mail came in as I was sending the last patch, here's another try.
> > this time only locking in sync() and only if the file is read-write.
> >
> > This should work, but there is one problem: configState is only set to
> > ReadOnly in
> > KConfig::isConfigWritable, which is normally not called, so there should
> > probably be
> > a call to it in KConfigPrivate::changeFileName, or this will not have much
> > effect.
> 
> 
> I thought I already made that change, I must have forgot to commit it,
> probably when I was having trouble getting a good update and had to get a
> clean checkout

I'm not sure what the current status is supposed to be (any uncommitted patch?), 
but I still see a lot of lock files created (or trying to be), both in /usr (no permissions) and in 
user-writable dirs (the lock file -can- be created, but why should it be, if we're only reading the file?)

strace -eopen kbuildsycoca4 2>&1 | grep lock   
open("/usr/share/applications/screensavers/gltext.desktop.lock.jI7373", O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0600) = -1 EACCES (Permission denied)
open("/d/kde/inst/kde4/share/applications/kde4/kghostview.desktop.lock.Ll7486", O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0600) = 15

Wow and even:
open("/home/dfaure/.kde4/share/kde4/servicetypes/plasma_applet.desktop.lock.Wy7373", O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0600) = 12
There is no /home/dfaure/.kde4/share/kde4/servicetypes/plasma_applet.desktop at all, why create a lock file there?
There is a $KDEDIR/share/kde4/servicetypes/plasma_applet.desktop but that's all.

-- 
David Faure, faure at kde.org, sponsored by Trolltech to work on KDE,
Konqueror (http://www.konqueror.org), and KOffice (http://www.koffice.org).