linux-kernel - RE: [PATCH 1/2] nohz: Affine unpinned timers to housekeepers

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Date:	Wed, 2 Sep 2015 19:03:42 +0000
From:	"Jiang, Yunhong" <yunhong.jiang@...el.com>
To:	Chris Metcalf <cmetcalf@...hip.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Vatika Harlalka <vatikaharlalka@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Preeti U Murthy" <preeti@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: RE: [PATCH 1/2] nohz: Affine unpinned timers to housekeepers

> -----Original Message-----
> From: Chris Metcalf [mailto:cmetcalf@...hip.com]
> Sent: Wednesday, September 2, 2015 9:17 AM
> To: Mike Galbraith; Frederic Weisbecker
> Cc: Jiang, Yunhong; Ingo Molnar; Peter Zijlstra; LKML; Vatika Harlalka; Thomas
> Gleixner; Preeti U Murthy; Christoph Lameter; Paul E . McKenney
> Subject: Re: [PATCH 1/2] nohz: Affine unpinned timers to housekeepers
> 
> On 09/02/2015 05:38 AM, Mike Galbraith wrote:
> > IMHO, nohz_full -> cpu_isolated_map removal really wants to happen.
> > NO_HZ_FULL_ALL currently means "Woohoo, next stop NR_CPUS=0".
> 
> Yeah, the problem seems to be folks who use it as a kind of
> "hey, maybe this gives me some optimization boost somewhere"
> kind of setting.  Did we ever hear actual use cases for people who
> benefited from running nohz_full on cpus with an active scheduler,
> i.e. no isolcpus for that core?  I find it hard to imagine, but, maybe...?
> 

I think they can use cpuset instead of isolcpus, like Viresh stated https://lkml.org/lkml/2014/4/14/199  .
This patch in fact removes one gap between cpuset and isolcpus.

Thanks
--jyh