linux-kernel - Re: [PATCH 21/22] Use a pre-calculated value instead of num_online

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Message-ID: <20090423004427.GD26643@csn.ul.ie>
Date:	Thu, 23 Apr 2009 01:44:27 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Linux Memory Management List <linux-mm@...ck.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 21/22] Use a pre-calculated value instead of
	num_online_nodes() in fast paths

On Wed, Apr 22, 2009 at 04:04:47PM -0700, David Rientjes wrote:
> On Wed, 22 Apr 2009, Mel Gorman wrote:
> 
> > diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> > index 848025c..474e73e 100644
> > --- a/include/linux/nodemask.h
> > +++ b/include/linux/nodemask.h
> > @@ -408,6 +408,19 @@ static inline int num_node_state(enum node_states state)
> >  #define next_online_node(nid)	next_node((nid), node_states[N_ONLINE])
> >  
> >  extern int nr_node_ids;
> > +extern int nr_online_nodes;
> > +
> > +static inline void node_set_online(int nid)
> > +{
> > +	node_set_state(nid, N_ONLINE);
> > +	nr_online_nodes = num_node_state(N_ONLINE);
> > +}
> > +
> > +static inline void node_set_offline(int nid)
> > +{
> > +	node_clear_state(nid, N_ONLINE);
> > +	nr_online_nodes = num_node_state(N_ONLINE);
> > +}
> >  #else
> >  
> >  static inline int node_state(int node, enum node_states state)
> 
> The later #define's of node_set_online() and node_set_offline() in 
> include/linux/nodemask.h should probably be removed now.
> 

You'd think, but you can enable memory hotplug without NUMA and
node_set_online() is called when adding memory. Even though those
functions are nops on !NUMA, they're necessary.

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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