From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juri Lelli Subject: [RFC PATCH 0/3] sched/deadline: cpuset: Rework DEADLINE bandwidth restoration Date: Wed, 15 Mar 2023 12:18:09 +0000 Message-ID: <20230315121812.206079-1-juri.lelli@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1678882745; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=fXppUTug8j7tzXh0MhllF73tJwxX1FkvEF1tk4ChKu4=; b=c9xF3/KHUaNc0z4boUNzGG2DBl2zP+JkhafBX++qhFPpcj94zF9AIjUY7Q1rtv+HutwVV3 BGwykW7J1sbNK5tez6H6hbHBIV55ZE2GocX0MbxfiUDhCE0MN+NMdYj/WR1JQAg/OiHMQ/ FkrZW0bYfLqp+h9bsU1G/+wr5YVwul0= List-ID: Content-Type: text/plain; charset="us-ascii" To: Peter Zijlstra , Ingo Molnar , Qais Yousef , Waiman Long , Tejun Heo , Zefan Li , Johannes Weiner , Hao Luo Cc: Dietmar Eggemann , Steven Rostedt , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, luca.abeni-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, claudio-YOzL5CV4y4YG1A2ADO40+w@public.gmane.org, tommaso.cucinotta-5rdYK369eBLQB0XuIGIEkQ@public.gmane.org, bristot-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, mathieu.poirier-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Vincent Guittot , Wei Wang , Rick Yiu , Quentin Perret , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sudeep Holla , Juri Lelli 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-wp2msK0BRk8tq7phqP6ubQ@public.gmane.org/ 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