Commit 56608209 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt

powerpc/numa: Set a smaller value for RECLAIM_DISTANCE to enable zone reclaim

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: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent b878dc00
...@@ -18,6 +18,16 @@ struct device_node; ...@@ -18,6 +18,16 @@ struct device_node;
*/ */
#define RECLAIM_DISTANCE 10 #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> #include <asm/mmzone.h>
static inline int cpu_to_node(int cpu) static inline int cpu_to_node(int cpu)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment