Re: [RFC/PATCH -v2] Add sysfs control to modify a user's cpu share

[Valdis.Kletnieks@vt.edu]

On Thu, 04 Oct 2007 10:54:51 +0200, Heiko Carstens said:
> >   echo 2048 > /sys/kernel/uids/500/cpu_share
> > 
> > this should just work too, regardless of there not being any UID 500 
> > tasks yet. Likewise, once configured, the /sys/kernel/uids/* directories 
> > (with the settings in them) should probably not go away either.
> 
> Shouldn't that be done via uevents? E.g. UID x gets added to the sysfs tree,
> generates a uevent and a script then figures out the cpu_share and sets it.

That would tend to be a tad racy - a site may want to set limits in the
hypothetical /sys/kernel/uids/NNN before the program has a chance to fork-bomb
or otherwise make it difficult to set a limitfrom within another userspace
process.  It's similar to why you want a process to be launched with all its
ulimit's set, rather than set them after the fork/exec happens...

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