On Tue 06-12-16 18:03:59, Huang Shijie wrote: > On Mon, Dec 05, 2016 at 05:31:01PM +0800, Michal Hocko wrote: > > On Mon 05-12-16 17:17:07, Huang Shijie wrote: > > [...] > > > The failure is caused by: > > > 1) kernel fails to allocate a gigantic page for the surplus case. > > > And the gather_surplus_pages() will return NULL in the end. > > > > > > 2) The condition checks for some functions are wrong: > > > return_unused_surplus_pages() > > > nr_overcommit_hugepages_store() > > > hugetlb_overcommit_handler() > > > > OK, so how is this any different from gigantic (1G) hugetlb pages on > I think there is no different from gigantic (1G) hugetlb pages on > x86_64. Do anyone ever tested the 1G hugetlb pages in x86_64 with the "counter.sh" > before? I suspect nobody has because the gigantic page support is still somehow coarse and from a quick look into the code we only support pre-allocated giga pages. In other words surplus pages and their accounting is not supported at all. I haven't yet checked your patchset but I can tell you one thing. Surplus and subpool pages code is tricky as hell. And it is not just a matter of teaching the huge page allocation code to do the right thing. There are subtle details all over the place. E.g. we currently do not free giga pages AFAICS. In fact I believe that the giga pages are kind of implanted to the existing code without any higher level consistency. This should change long term. But I am worried it is much more work. Now I might be wrong because I might misremember things which might have been changed recently but please make sure you describe the current state and changes of giga pages when touching this area much better if you want to pursue this route... Thanks! -- 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>