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

Waiman Long
2023-04-18T14:31:27Z

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.

Thanks,
Longman