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

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Message-ID: <20230731172306.GE232229@lorien.usersys.redhat.com>
Date:   Mon, 31 Jul 2023 13:23:06 -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>
Subject: Re: [PATCH v6 0/2] Fix nohz_full vs cfs bandwidth


Sorry, ignore duplicate, please.  Apparently I forgot email while
on PTO last week :)

On Mon, Jul 31, 2023 at 12:38:37PM -0400 Phil Auld wrote:
> Hi Peter,
> 
> On Wed, Jul 12, 2023 at 09:33:55AM -0400 Phil Auld wrote:
> > 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
> > 
> 
> Ping :)
> 
> Any thoughts on these now?
> 
> 
> Cheers,
> Phil
> 
> 
> -- 
> 

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