On Sat, 28 May 2011, Michal Hocko wrote:
> > --- a/include/linux/nodemask.h~cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-fix-2
> > +++ a/include/linux/nodemask.h
> > @@ -433,8 +433,6 @@ static inline void node_set_offline(int
> > nr_online_nodes = num_node_state(N_ONLINE);
> > }
> >
> > -extern int node_random(const nodemask_t *maskp);
> > -
> > #else
> >
> > static inline int node_state(int node, enum node_states state)
> > @@ -466,7 +464,15 @@ static inline int num_node_state(enum no
> > #define node_set_online(node) node_set_state((node), N_ONLINE)
> > #define node_set_offline(node) node_clear_state((node), N_ONLINE)
> >
> > -static inline int node_random(const nodemask_t *mask) { return 0; }
> > +#endif
> > +
> > +#if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1)
> > +extern int node_random(const nodemask_t *maskp);
> > +#else
> > +static inline int node_random(const nodemask_t *mask)
> > +{
> > + return 0;
> > +}
> > #endif
>
> I have to admit that I quite don't understand concept of several nodes
> with UMA archs but do we really want to provide the sane node all the
> time?
>
They aren't nodes on UMA machines, they are memory regions for
DISCONTIGMEM which are separated by large holes in the address space.
These archs will never sanely use node_random(), so it doesn't really
matter except for CONFIG_NUMA where MAX_NUMNODES > 1, since they won't be
selecting random memory regions.
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