On Fri, 14 Sep 2012, Andrew Morton wrote: Hi Andrew, at first thanks for your review! > On Fri, 14 Sep 2012 23:22:47 +0200 > Petr Holasek <pholasek@xxxxxxxxxx> wrote: > > > Introduces new sysfs boolean knob /sys/kernel/mm/ksm/merge_nodes > > I wonder if merge_across_nodes would be a better name. > Agreed. > > which control merging pages across different numa nodes. > > When it is set to zero only pages from the same node are merged, > > otherwise pages from all nodes can be merged together (default behavior). > > > > Typical use-case could be a lot of KVM guests on NUMA machine > > and cpus from more distant nodes would have significant increase > > of access latency to the merged ksm page. Sysfs knob was choosen > > for higher scalability. > > Well... what is the use case for merge_nodes=0? IOW, why shouldn't we > make this change non-optional and avoid the sysfs knob? I assume that there are still some users who want to use KSM mainly for saving of physical memory and access latency is not priority for them. > > > > This patch also adds share_all sysfs knob which can be used for adding > > all anon vmas of all processes in system to ksmd scan queue. Knob can be > > triggered only when run knob is set to zero. > > I really don't understand this share_all thing. From reading the code, > it is a once-off self-resetting trigger thing. Why? How is one to use > this? What's the benefit? What's the effect? I introduced it on the basis of our discussion about v2 patch https://lkml.org/lkml/2012/6/29/426 as some knob which can madvise all anon mappings with MADV_MERGEABLE. But I might have misunderstood your idea. If you don't like current self-resetting trigger we either can implement it as stable 0/1 knob that would madvise all current and future anon mappings when set to 1 or completely exclude this share_all thing from the patch. I am going to fix all all mistakes you pointed out in your review as well as add more verbose documentation and comments in next version. thanks, Petr H -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>