[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <20230315121812.206079-1-juri.lelli@redhat.com>
Date: Wed, 15 Mar 2023 12:18:09 +0000
From: Juri Lelli <juri.lelli@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Qais Yousef <qyousef@...alina.io>,
Waiman Long <longman@...hat.com>, Tejun Heo <tj@...nel.org>,
Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Hao Luo <haoluo@...gle.com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
bristot@...hat.com, mathieu.poirier@...aro.org,
cgroups@...r.kernel.org,
Vincent Guittot <vincent.guittot@...aro.org>,
Wei Wang <wvw@...gle.com>, Rick Yiu <rickyiu@...gle.com>,
Quentin Perret <qperret@...gle.com>,
Heiko Carstens <hca@...ux.ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Alexander Gordeev <agordeev@...ux.ibm.com>,
Sudeep Holla <sudeep.holla@....com>,
Juri Lelli <juri.lelli@...hat.com>
Subject: [RFC PATCH 0/3] sched/deadline: cpuset: Rework DEADLINE bandwidth restoration
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
Powered by blists - more mailing lists