From 9eeff2395e3cfd05c9b2e6074ff943a34b0c5c21 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Wed, 18 Jan 2006 17:42:31 -0800 Subject: [PATCH] Zone reclaim: Reclaim logic Some bits for zone reclaim exists in 2.6.15 but they are not usable. This patch fixes them up, removes unused code and makes zone reclaim usable. Zone reclaim allows the reclaiming of pages from a zone if the number of free pages falls below the watermarks even if other zones still have enough pages available. Zone reclaim is of particular importance for NUMA machines. It can be more beneficial to reclaim a page than taking the performance penalties that come with allocating a page on a remote zone. Zone reclaim is enabled if the maximum distance to another node is higher than RECLAIM_DISTANCE, which may be defined by an arch. By default RECLAIM_DISTANCE is 20. 20 is the distance to another node in the same component (enclosure or motherboard) on IA64. The meaning of the NUMA distance information seems to vary by arch. If zone reclaim is not successful then no further reclaim attempts will occur for a certain time period (ZONE_RECLAIM_INTERVAL). This patch was discussed before. See http://marc.theaimsgroup.com/?l=linux-kernel&m=113519961504207&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=113408418232531&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=113389027420032&w=2 http://marc.theaimsgroup.com/?l=linux-kernel&m=113380938612205&w=2 Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/topology.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include/linux/topology.h') diff --git a/include/linux/topology.h b/include/linux/topology.h index 315a5163d6a0..e8eb0040ce3a 100644 --- a/include/linux/topology.h +++ b/include/linux/topology.h @@ -56,6 +56,14 @@ #define REMOTE_DISTANCE 20 #define node_distance(from,to) ((from) == (to) ? LOCAL_DISTANCE : REMOTE_DISTANCE) #endif +#ifndef RECLAIM_DISTANCE +/* + * If the distance between nodes in a system is larger than RECLAIM_DISTANCE + * (in whatever arch specific measurement units returned by node_distance()) + * then switch on zone reclaim on boot. + */ +#define RECLAIM_DISTANCE 20 +#endif #ifndef PENALTY_FOR_NODE_WITH_CPUS #define PENALTY_FOR_NODE_WITH_CPUS (1) #endif -- cgit v1.2.3