linux-kernel - Re: [PATCH 2/2] sched/deadline: Correctly account for allocated bandwidth during hotplug

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Message-ID: <ZzS-ncIOnEgrOlte@jlelli-thinkpadt14gen4.remote.csb>
Date: Wed, 13 Nov 2024 14:58:37 +0000
From: Juri Lelli <juri.lelli@...hat.com>
To: Phil Auld <pauld@...hat.com>
Cc: Waiman Long <longman@...hat.com>, Tejun Heo <tj@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Koutny <mkoutny@...e.com>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Qais Yousef <qyousef@...alina.io>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	"Joel Fernandes (Google)" <joel@...lfernandes.org>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Aashish Sharma <shraash@...gle.com>,
	Shin Kawamura <kawasin@...gle.com>,
	Vineeth Remanan Pillai <vineeth@...byteword.org>,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH 2/2] sched/deadline: Correctly account for allocated
 bandwidth during hotplug

Hi Phil,

On 13/11/24 08:49, Phil Auld wrote:
> 
> Hi Juri,
> 
> On Wed, Nov 13, 2024 at 12:57:23PM +0000 Juri Lelli wrote:
> > For hotplug operations, DEADLINE needs to check that there is still enough
> > bandwidth left after removing the CPU that is going offline. We however
> > fail to do so currently.
> > 
> > Restore the correct behavior by restructuring dl_bw_manage() a bit, so
> > that overflow conditions (not enough bandwidth left) are properly
> > checked. Also account for dl_server bandwidth, i.e. discount such
> > bandwidht in the calculation since NORMAL tasks will be anyway moved
> 
> "bandwidth"  :)

Grrrr. :)

> 
> 
> > away from the CPU as a result of the hotplug operation.
> >
> 
> LGTM.
> 
> Reviewed-by: Phil Auld <pauld@...hat.com>

Thanks!
Juri