Messages in this thread | | | Date | Thu, 19 Mar 2009 22:33:53 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH 20/35] Use a pre-calculated value for num_online_nodes() |
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On Thu, Mar 19, 2009 at 06:22:38PM -0400, Christoph Lameter wrote: > On Thu, 19 Mar 2009, Mel Gorman wrote: > > > This patch actually alters the API. node_set_online() called when > > MAX_NUMNODES == 1 will now fail to compile. That situation wouldn't make > > any sense anyway but is it intentional? > > Yes MAX_NUMNODES means that this is not a NUMA configuration. Setting an > ode online would make no sense. Node 0 is always online. >
Right.
> > For reference here is the patch I had for a similar goal which kept the > > API as it was. I'll drop it if you prefer your own version. > > Lets look through it and get the best pieces from both. >
I posted an amalgamation. Sorry for the cross-over mails but I wanted to get tests going before I fell asleep. They take a few hours to complete.
> > static inline void node_set_state(int node, enum node_states state) > > { > > __node_set(node, &node_states[state]); > > + if (state == N_ONLINE) > > + nr_online_nodes = num_node_state(N_ONLINE); > > } > > That assumes uses of node_set_state N_ONLINE. Are there such users or are > all using node_set_online()? >
node_set_online() calls node_set_state(node, N_ONLINE) so it should have worked out.
> > @@ -449,7 +457,8 @@ static inline int num_node_state(enum node_states state) > > node; \ > > }) > > > > -#define num_online_nodes() num_node_state(N_ONLINE) > > + > > +#define num_online_nodes() (nr_online_nodes) > > #define num_possible_nodes() num_node_state(N_POSSIBLE) > > #define node_online(node) node_state((node), N_ONLINE) > > #define node_possible(node) node_state((node), N_POSSIBLE) > > Hmmmm... Yes we could get rid of those. > > I'd also like to see nr_possible_nodes(). nr_possible_nodes is important > if you want to check if the system could ever bring up a second node > (which would make the current optimization not viable) whereas > nr_online_nodes is the check for how many nodes are currently online. >
I redid your patch to drop the nr_possible_nodes() because I couldn't convince myself it was correct in all cases and it isn't as important as avoiding num_online_nodes() in fast paths.
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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