Messages in this thread | | | From | Juri Lelli <> | Subject | [RFC PATCH 0/3] sched/deadline: cpuset: Rework DEADLINE bandwidth restoration | Date | Wed, 15 Mar 2023 12:18:09 +0000 |
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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 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
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@layalina.io/
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
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