On 03/15/23 12:18, 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!). Thanks a lot for this! And sorry I couldn't provide something better. > > To fix the problem I instead would propose we > > 1 - 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) > 2 - Keep track of the number of DEADLINE tasks belonging to each cpuset > 3 - 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 nit: Would you consider adding another patch to rename the functions? rebuild_root_domains() and update_tasks_root_domain() are deadline accounting specific functions and don't actually rebuild root domains. Thanks! -- Qais Yousef > > This set is also available from > > https://github.com/jlelli/linux.git deadline/rework-cpusets > > Feedback is more than welcome. > > Best, > Juri > > 1 - https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@xxxxxxxxxxx/ > > Juri Lelli (3): > sched/cpuset: Bring back cpuset_mutex > sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets > cgroup/cpuset: Iterate only if DEADLINE tasks are present > > include/linux/cpuset.h | 12 ++- > kernel/cgroup/cgroup.c | 4 + > kernel/cgroup/cpuset.c | 175 +++++++++++++++++++++++------------------ > kernel/sched/core.c | 32 ++++++-- > 4 files changed, 137 insertions(+), 86 deletions(-) > > -- > 2.39.2 >
