linux-kernel - Re: [PATCH] online CPU before memory failed in pcpu_alloc

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Message-Id: <1274445129.9131.9.camel@useless.americas.hpqcorp.net>
Date:	Fri, 21 May 2010 08:32:09 -0400
From:	Lee Schermerhorn <Lee.Schermerhorn@...com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	minskey guo <chaohong_guo@...ux.intel.com>, linux-mm@...ck.org,
	prarit@...hat.com, andi.kleen@...el.com,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	stable@...nel.org
Subject: Re: [PATCH] online CPU before memory failed in pcpu_alloc_pages()

On Fri, 2010-05-21 at 13:44 +0900, KAMEZAWA Hiroyuki wrote:
> On Fri, 21 May 2010 10:55:12 +1000
> Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> 
> > Hi Andrew,
> > 
> > On Thu, 20 May 2010 13:43:59 -0700 Andrew Morton <akpm@...ux-foundation.org> wrote:
> > >
> > > > --- a/mm/percpu.c
> > > > +++ b/mm/percpu.c
> > > > @@ -714,13 +714,29 @@ static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
> > > 
> > > In linux-next, Tejun has gone and moved pcpu_alloc_pages() into the new
> > > mm/percpu-vm.c.  So either
> > 
> > This has gone into Linus' tree today ...
> > 
> 
> Hmm, a comment here.
> 
> Recently, Lee Schermerhorn developed
> 
>  numa-introduce-numa_mem_id-effective-local-memory-node-id-fix2.patch
> 
> Then, you can use cpu_to_mem() instead of cpu_to_node() to find the
> nearest available node.
> I don't check cpu_to_mem() is synchronized with NUMA hotplug but
> using cpu_to_mem() rather than adding 
> =
> 
> +			if ((nid == -1) ||
> +			    !(node_zonelist(nid, GFP_KERNEL)->_zonerefs->zone))
> +				nid = numa_node_id();
> +
> ==
> 
> is better. 


Kame-san, all:

numa_mem_id() and cpu_to_mem() are not supported [yet] on x86 because
x86 hides all memoryless nodes and moves cpus to "nearby" [for some
definition thereof] nodes with memory.  So, these interfaces just return
numa_node_id() and cpu_to_node() for x86.  Perhaps that will change
someday...

Lee


> 
> Thanks,
> -Kame
> 
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