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-rw-r--r--Documentation/vm/ksm.txt16
1 files changed, 12 insertions, 4 deletions
diff --git a/Documentation/vm/ksm.txt b/Documentation/vm/ksm.txt
index 25cc89ba811b..f34a8ee6f860 100644
--- a/Documentation/vm/ksm.txt
+++ b/Documentation/vm/ksm.txt
@@ -60,10 +60,18 @@ sleep_millisecs - how many milliseconds ksmd should sleep before next scan
merge_across_nodes - specifies if pages from different numa nodes can be merged.
When set to 0, ksm merges only pages which physically
- reside in the memory area of same NUMA node. It brings
- lower latency to access to shared page. Value can be
- changed only when there is no ksm shared pages in system.
- Default: 1
+ reside in the memory area of same NUMA node. That brings
+ lower latency to access of shared pages. Systems with more
+ nodes, at significant NUMA distances, are likely to benefit
+ from the lower latency of setting 0. Smaller systems, which
+ need to minimize memory usage, are likely to benefit from
+ the greater sharing of setting 1 (default). You may wish to
+ compare how your system performs under each setting, before
+ deciding on which to use. merge_across_nodes setting can be
+ changed only when there are no ksm shared pages in system:
+ set run 2 to unmerge pages first, then to 1 after changing
+ merge_across_nodes, to remerge according to the new setting.
+ Default: 1 (merging across nodes as in earlier releases)
run - set 0 to stop ksmd from running but keep merged pages,
set 1 to run ksmd e.g. "echo 1 > /sys/kernel/mm/ksm/run",