linux-kernel - Re: [PATCH v2] cpusets: randomize node rotor used in cpuset_mem_spread

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Message-Id: <20110415172855.12FF.A69D9226@jp.fujitsu.com>
Date:	Fri, 15 Apr 2011 17:29:00 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	kosaki.motohiro@...fujitsu.com,
	LKML <linux-kernel@...r.kernel.org>,
	Jack Steiner <steiner@....com>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Paul Menage <menage@...gle.com>, Robin Holt <holt@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-mm@...ck.org
Subject: Re: [PATCH v2] cpusets: randomize node rotor used in cpuset_mem_spread_node()

> [I just realized that I forgot to CC mm mailing list]
> 
> On Fri 15-04-11 16:18:45, KOSAKI Motohiro wrote:
> > Oops.
> > I should have look into !mempolicy part too.
> > I'm sorry.
> > 
> [...]
> > Michal, I think this should be
> > 
> > #ifdef CONFIG_CPUSETS
> > 	if (cpuset_do_page_mem_spread())
> > 		p->cpuset_mem_spread_rotor = node_random(&p->mems_allowed);
> > 	if (cpuset_do_slab_mem_spread())
> > 		p->cpuset_slab_spread_rotor = node_random(&p->mems_allowed);
> > #endif
> > 
> > because 99.999% people don't use cpuset's spread mem/slab feature and
> > get_random_int() isn't zero cost.
> > 
> > What do you think?
> 
> You are right. I was thinking about lazy approach and initialize those
> values when they are used for the first time. What about the patch
> below?
> 
> Change from v1:
> - initialize cpuset_{mem,slab}_spread_rotor lazily

Yeah! This is much much better than mine. Thank you!
	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>



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