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page allocator: use a pre-calculated value instead of num_online_nodes() in fast paths

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num_online_nodes() is called in a number of places but most often by the
page allocator when deciding 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 updates the
value when nodes get onlined and offlined.  The value is then used in a
number of important paths in place of num_online_nodes().

[rientjes@google.com: do not override definition of node_set_online() with macro]
Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Lameter 2009-06-16 15:32:15 -07:00 • committed by Linus Torvalds
parent 974709bdb2
commit 62bc62a873
5 changed files with 26 additions and 11 deletions
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19
include/linux/nodemask.h
View file

@ -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)
@ -434,7 +447,10 @@ static inline int num_node_state(enum node_states state)
#define first_online_node 0
#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]
@ -454,9 +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)