linux-kernel - Re: [PATCH 2/6] change alloc function in pcpu_alloc

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Date:	Mon, 19 Apr 2010 00:55:45 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Bob Liu <lliubbo@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH 2/6] change alloc function in pcpu_alloc_pages

Hi, Lee. 

On Fri, 2010-04-16 at 15:13 -0400, Lee Schermerhorn wrote:
> On Fri, 2010-04-16 at 11:07 -0500, Christoph Lameter wrote:
> > On Thu, 15 Apr 2010, Minchan Kim wrote:
> > 
> > > I don't want to remove alloc_pages for UMA system.
> > 
> > alloc_pages is the same as alloc_pages_any_node so why have it?
> > 
> > > #define alloc_pages alloc_page_sexact_node
> > >
> > > What I want to remove is just alloc_pages_node. :)
> > 
> > Why remove it? If you want to get rid of -1 handling then check all the
> > callsites and make sure that they are not using  -1.
> > 
> > Also could you define a constant for -1? -1 may have various meanings. One
> > is the local node and the other is any node. 
> 
> NUMA_NO_NODE is #defined as (-1) and can be used for this purpose.  '-1'
> has been replaced by this in many cases.   It can be interpreted as "No
> node specified" == "any node is acceptable".  But, it also has multiple
> meanings.  E.g., in the hugetlb sysfs attribute and sysctl functions it
> indicates the global hstates [all nodes] vs a per node hstate.  So, I
> suppose one could define a NUMA_ANY_NODE, to make the intention clear at
> the call site.
> 
> I believe that all usage of -1 to mean the local node has been removed,
> unless I missed one.  Local allocation is now indicated by a mempolicy
> mode flag--MPOL_F_LOCAL.  It's treated as a special case of
> MPOL_PREFERRED.

Thanks for good information. :)

-- 
Kind regards,
Minchan Kim


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