On Fri 05-04-13 07:41:23, Wanpeng Li wrote: > On Thu, Apr 04, 2013 at 06:17:46PM +0200, 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. > > Gigantic huge pages in hugetlb means h->order >= MAX_ORDER instead of GB > pages. ;-) Yes, I am aware of that but the question remains the same (and unanswered). What is the use case? -- 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>