linux-kernel - [PATCH v6 0/2] Fix nohz

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Message-Id: <20230712133357.381137-1-pauld@redhat.com>
Date:   Wed, 12 Jul 2023 09:33:55 -0400
From:   Phil Auld <pauld@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Juri Lelli <juri.lelli@...hat.com>, Ingo Molnar <mingo@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Valentin Schneider <vschneid@...hat.com>,
        Ben Segall <bsegall@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mel Gorman <mgorman@...e.de>,
        Frederic Weisbecker <frederic@...nel.org>,
        Tejun Heo <tj@...nel.org>, Phil Auld <pauld@...hat.com>
Subject: [PATCH v6 0/2] Fix nohz_full vs cfs bandwidth

This is v6 of patch 2/2 which is adding code to prevent
the tick from being stopped when the single running task
has bandwidth limits. Discussions had led to the idea of
adding a bit to task_struct to help make this decision.

There was some complexity with doing it in the task which
is  avoided by using something in the cfs_rq. Looking 
into that lead me to the hierarchical_quota field in the 
cfs_bandwith struct. We spend a good deal of effort
updating (or trying to, see patch 1/2) that value for
the whole task_group tree when a quota is set/changed.

This new version first fixes that value to be meaningful
for cgroupv2 and then leverages it to make the decisions
about blocking the tick_stop. 

Phil Auld (2):
  sched, cgroup: Restore meaning to hierarchical_quota
  Sched/fair: Block nohz tick_stop when cfs bandwidth in use

 kernel/sched/core.c     | 23 ++++++++++++++---
 kernel/sched/fair.c     | 56 ++++++++++++++++++++++++++++++++++++++---
 kernel/sched/features.h |  2 ++
 kernel/sched/sched.h    |  3 ++-
 4 files changed, 76 insertions(+), 8 deletions(-)

-- 
2.31.1