Re: [PATCH] scheduling priorities with rlimit

[utz lehmann <lkml@s2y4n2c.de>]

On Sun, 2005-01-09 at 20:06 +0100, Arjan van de Ven wrote:
> On Sun, 2005-01-09 at 18:15 +0100, utz lehmann wrote:
> > Hi
> > 
> > I really like the idea of controlling the maximum settable scheduling
> > priorities via rlimit. See the Realtime LSM thread. I want to give users
> > the right to raise the priority of previously niced jobs.
> > 
> > I have modified Chris Wright's patch (against 2.6.10):
> > (http://marc.theaimsgroup.com/?l=linux-kernel&m=110513793228776&w=2)
> > 
> > - allow always to increase nice levels (lower priority).
> > - set the default for RLIMIT_PRIO to 0.
> > - add the other architectures.
> > 
> > With this the default is compatible with the old behavior.
> > 
> > With RLIMIT_PRIO > 0 a user is able to raise the priority up to the
> > value. 0-39 for nice levels 19 .. -20, 40-139 for realtime priorities
> > (0 .. 99).
> 
> this is a bit of an awkward interface don't you think?
> I much rather have the rlimit match the exact nice values we communicate
> to userspace elsewhere, both to be consistent and to not expose
> scheduler internals to userpsace.

Yes it is. But rlimits are unsigned .-( (asm/resource.h says this).
I prefer rlimit match nice value too, but how to do this with unsigned.
And what do with the RT prio, different rlimit?
Btw: I saw this on a solaris command too, 0-39 for nice, 40-139 for RT
(dont rememer which).

>
> Also I like the idea of allowing sysadmins to make certain users/groups
> nice levels 5 and higher (think a university machine that makes all
> students nice 5 and higher only, while giving staff 0 and higher, and
> the sysadmin -5 and higher ;)

You can do this already. "priority" item in /etc/security/limits.conf.
But they can only lower the priority.
This patch is for allowing to raise it.