linux-kernel - Re: [PATCH] workqueue: avoid nohz

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Date:	Tue, 31 Mar 2015 22:58:41 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	cmetcalf@...hip.com
Cc:	Tejun Heo <tj@...nel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] workqueue: avoid nohz_full cores

On Tue, Mar 31, 2015 at 03:25:59PM -0400, cmetcalf@...hip.com wrote:
> From: Chris Metcalf <cmetcalf@...hip.com>
> 
> When queuing work, we should avoid queuing it on the local cpu if
> we are using WORK_CPU_UNBOUND and the local cpu is nohz_full, since
> the workqueue will mean a later interrupt of the nohz_full process
> that presumably would prefer continuing to have 100% of the core
> without interrupts.
> 
> Likewise, remove the nohz_full cores from unbound workqueues.  If
> all the cores are nohz_full, we leave them in.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...hip.com>

Lai is already working on this: https://lkml.org/lkml/2015/3/12/27

All that will be needed after this patchset is to force the desired
unbound workqueue mask on boot.
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