Re: [patch, 2.6.11-rc2] sched: RLIMIT_RT_CPU feature, -D7

[Peter Williams]

Ingo Molnar wrote:
> * Peter Williams <pwil3058@xxxxxxxxxxxxxx> wrote:
>
>
> > Oops, after rereading the patch, a task that set its RT_CPU_RATIO
> > rlimit to zero wouldn't be escaping the mechanism at all.  It would be
> > suffering maximum throttling. [...]
>
>
> my intention was to let 'limit 0' mean 'old RT semantics' - i.e. 'no RT
> CPU time for unprivileged tasks at all', and only privileged tasks may
> do it and then they'll get full CPU time with no throttling.
>
> so in that context your observation highlights another bug, which i
> fixed in the -D7 patch available from the usual place:
>
>   http://redhat.com/~mingo/rt-limit-patches/
>
> not doing the '0' exception would make it harder to introduce the rlimit
> in a compatible fashion. (My current thinking is that the default RT_CPU
> rlimit should be 0.)

One solution to this dilemma might be to set a PF_FLAG on a task 
whenever it gains RT status via this privilege bypass and only apply the 
limit to tasks that have that flag set.

Peter
--
Peter Williams                                   pwil3058@xxxxxxxxxxxxxx

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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