On 15/03/23 14:55, Qais Yousef wrote: > 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. Ah, no worries. Actually still have to convice myself what I have it's actually 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. Yep, can do. Thanks, Juri
