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
Thanks a lot Juri!
I picked up the updated series and applied them to a 5.10 kernel and tested the
issue is fixed. Replied with my reviewed-and-tested-bys to some of the patches
already.
I haven't looked much at Dietmar's patches and while they were part of the
test, but there are no dl tasks on the system so I felt hesitant to say
I tested that part.
Cheers
--
Qais Yousef
