On Thu 04-04-13 18:17:46, Michal Hocko wrote: > On Thu 04-04-13 17:09:08, Wanpeng Li wrote: > > order >= MAX_ORDER pages are only allocated at boot stage using the > > bootmem allocator with the "hugepages=xxx" option. These pages are never > > free after boot by default since it would be a one-way street(>= MAX_ORDER > > pages cannot be allocated later), but if administrator confirm not to > > use these gigantic pages any more, these pinned pages will waste memory > > since other users can't grab free pages from gigantic hugetlb pool even > > if OOM, it's not flexible. The patchset add hugetlb gigantic page pools > > shrink supporting. Administrator can enable knob exported in sysctl to > > permit to shrink gigantic hugetlb pool. > > I am not sure I see why the new knob is needed. > /sys/kernel/mm/hugepages/hugepages-*/nr_hugepages is root interface so > an additional step to allow writing to the file doesn't make much sense > to me to be honest. > > Support for shrinking gigantic huge pages makes some sense to me but I > would be interested in the real world example. GB pages are usually used > in very specific environments where the amount is usually well known. > > I could imagine nr_hugepages_mempolicy would make more sense to free > pages from particular nodes so they could be offlined for example. > Does the patchset handles this as well? Ohh, I should have checked before asking. Both knobs use the same hugetlb_sysctl_handler_common and unless there is something hardcoded in the patches then it should be supproted. -- Michal Hocko SUSE Labs -- 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>