Re: [PATCH 20/35] Use a pre-calculated value for num_online_nodes()

[Nick Piggin]

On Mon, Mar 16, 2009 at 10:42:34PM +1100, Nick Piggin wrote:
> On Monday 16 March 2009 20:46:15 Mel Gorman wrote:
> > num_online_nodes() is called by the page allocator to decide whether the
> > zonelist needs to be filtered based on cpusets or the zonelist cache.
> > This is actually a heavy function and touches a number of cache lines.
> > This patch stores the number of online nodes at boot time and when
> > nodes get onlined and offlined.
> >
> > Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
> > ---
> >  include/linux/nodemask.h |   16 ++++++++++++++--
> >  mm/page_alloc.c          |    6 ++++--
> >  2 files changed, 18 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> > index 848025c..4749e30 100644
> > --- a/include/linux/nodemask.h
> > +++ b/include/linux/nodemask.h
> > @@ -449,13 +449,25 @@ static inline int num_node_state(enum node_states
> > state) node;					\
> >  })
> >
> > +/* Recorded value for num_online_nodes() */
> > +extern int static_num_online_nodes;
> 
> __read_mostly, please. Check this for any other place you've added
> global cachelines that are referenced by the allocator.

OK I'm blind, sorry ignore that :P
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