Re: [PATCH 0/6] sched/deadline: cpuset: Rework DEADLINE bandwidth restoration

Juri Lelli
2023-04-20T14:15:33Z

On 18/04/23 10:31, Waiman Long wrote:
> On 4/18/23 10:11, Qais Yousef wrote:
> > On 03/29/23 14:55, Juri Lelli wrote:
> > > Qais reported [1] that iterating over all tasks when rebuilding root
> > > domains for finding out which ones are DEADLINE and need their bandwidth
> > > correctly restored on such root domains can be a costly operation (10+
> > > ms delays on suspend-resume). He proposed we skip rebuilding root
> > > domains for certain operations, but that approach seemed arch specific
> > > and possibly prone to errors, as paths that ultimately trigger a rebuild
> > > might be quite convoluted (thanks Qais for spending time on this!).
> > >
> > > To fix the problem
> > >
> > > 01/06 - Rename functions deadline with DEADLINE accounting (cleanup
> > > suggested by Qais) - no functional change
> > > 02/06 - Bring back cpuset_mutex (so that we have write access to cpusets
> > > from scheduler operations - and we also fix some problems
> > > associated to percpu_cpuset_rwsem)
> > > 03/06 - Keep track of the number of DEADLINE tasks belonging to each cpuset
> > > 04/06 - Create DL BW alloc, free & check overflow interface for bulk
> > > bandwidth allocation/removal - no functional change
> > > 05/06 - Fix bandwidth allocation handling for cgroup operation
> > > involving multiple tasks
> > > 06/06 - Use this information to only perform the costly iteration if
> > > DEADLINE tasks are actually present in the cpuset for which a
> > > corresponding root domain is being rebuilt
> > >
> > > With respect to the RFC posting [2]
> > >
> > > 1 - rename DEADLINE bandwidth accounting functions - Qais
> > > 2 - call inc/dec_dl_tasks_cs from switched_{to,from}_dl - Qais
> > > 3 - fix DEADLINE bandwidth allocation with multiple tasks - Waiman,
> > > contributed by Dietmar
> > >
> > > This set is also available from
> > >
> > > https://github.com/jlelli/linux.git deadline/rework-cpusets
> > Is this just waiting to be picked up or still there's something to be addressed
> > still?
>
> There are some changes to cpuset code recently and so I believe that this
> patch series may need to be refreshed to reconcile the changes.

Yeah, will soon take a look.

Thanks!
Juri