From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 17 May 2010 16:19:56 +1000 From: Anton Blanchard To: benh@kernel.crashing.org Subject: [PATCH 1/3] powerpc: numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim Message-ID: <20100517061956.GE13509@kryten> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , I noticed /proc/sys/vm/zone_reclaim_mode was 0 on a ppc64 NUMA box. It gets enabled via this: /* * If another node is sufficiently far away then it is better * to reclaim pages in a zone before going off node. */ if (distance > RECLAIM_DISTANCE) zone_reclaim_mode = 1; Since we use the default value of 20 for REMOTE_DISTANCE and 20 for RECLAIM_DISTANCE it never kicks in. The local to remote bandwidth ratios can be quite large on System p machines so it makes sense for us to reclaim clean pagecache locally before going off node. The patch below sets a smaller value for RECLAIM_DISTANCE and thus enables zone reclaim. Signed-off-by: Anton Blanchard --- Index: powerpc.git/arch/powerpc/include/asm/topology.h =================================================================== --- powerpc.git.orig/arch/powerpc/include/asm/topology.h 2010-05-17 12:56:02.000000000 +1000 +++ powerpc.git/arch/powerpc/include/asm/topology.h 2010-05-17 15:01:37.514703571 +1000 @@ -18,6 +18,16 @@ struct device_node; */ #define RECLAIM_DISTANCE 10 +/* + * Before going off node we want the VM to try and reclaim from the local + * node. It does this if the remote distance is larger than RECLAIM_DISTANCE. + * With the default REMOTE_DISTANCE of 20 and the default RECLAIM_DISTANCE of + * 20, we never reclaim and go off node straight away. + * + * To fix this we choose a smaller value of RECLAIM_DISTANCE. + */ +#define RECLAIM_DISTANCE 10 + #include static inline int cpu_to_node(int cpu)