From: Anton Blanchard <anton@samba.org>
To: benh@kernel.crashing.org
Cc: linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 1/3] powerpc: numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim
Date: Mon, 17 May 2010 16:19:56 +1000 [thread overview]
Message-ID: <20100517061956.GE13509@kryten> (raw)
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 <anton@samba.org>
---
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 <asm/mmzone.h>
static inline int cpu_to_node(int cpu)
next reply other threads:[~2010-05-17 6:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-17 6:19 Anton Blanchard [this message]
2010-05-17 6:21 ` [PATCH 2/3] powerpc: numa: Use ibm,architecture-vec-5 to detect form 1 affinity Anton Blanchard
2010-05-17 6:22 ` [PATCH 3/3] powerpc: numa: Use form 1 affinity to setup node distance Anton Blanchard
2010-05-17 6:28 ` [PATCH 2/3] powerpc: numa: Use ibm,architecture-vec-5 to detect form 1 affinity Anton Blanchard
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