Re: [PATCH 21/22] Use a pre-calculated value instead of num_online_nodes() in fast paths

David Rientjes
2009-04-23T19:29:46Z

On Thu, 23 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.
>

The problem is that your new functions above are never used because
node_set_online and node_set_offline are macro defined later in this
header for all cases, not just !CONFIG_NUMA.

You need this.
---
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -448,6 +448,9 @@ static inline int num_node_state(enum node_states state)
#define next_online_node(nid) (MAX_NUMNODES)
#define nr_node_ids 1
#define nr_online_nodes 1
+
+#define node_set_online(node) node_set_state((node), N_ONLINE)
+#define node_set_offline(node) node_clear_state((node), N_ONLINE)
#endif

#define node_online_map node_states[N_ONLINE]
@@ -467,9 +470,6 @@ static inline int num_node_state(enum node_states state)
#define node_online(node) node_state((node), N_ONLINE)
#define node_possible(node) node_state((node), N_POSSIBLE)

-#define node_set_online(node) node_set_state((node), N_ONLINE)
-#define node_set_offline(node) node_clear_state((node), N_ONLINE)
-
#define for_each_node(node) for_each_node_state(node, N_POSSIBLE)
#define for_each_online_node(node) for_each_node_state(node, N_ONLINE)