On Thu 14-03-13 19:24:11, Wanpeng Li wrote: > On Thu, Mar 14, 2013 at 12:09:27PM +0100, Michal Hocko wrote: > >On Thu 14-03-13 18:49:49, Wanpeng Li wrote: > >> Changelog: > >> v1 -> v2: > >> * update patch description, spotted by Michal > >> > >> hugetlb_total_pages() does not account for all the supported hugepage > >> sizes. > > > >> This can lead to incorrect calculation of the total number of > >> page frames used by hugetlb. This patch corrects the issue. > > > > Hi Michal, > > >Sorry to be so picky but this doesn't tell us much. Why do we need to > >have the total number of hugetlb pages? > > > >What about the following: > >"hugetlb_total_pages is used for overcommit calculations but the > >current implementation considers only default hugetlb page size (which > >is either the first defined hugepage size or the one specified by > >default_hugepagesz kernel boot parameter). > > > >If the system is configured for more than one hugepage size (which is > >possible since a137e1cc hugetlbfs: per mount huge page sizes) then > >the overcommit estimation done by __vm_enough_memory (resp. shown by > >meminfo_proc_show) is not precise - there is an impression of more > >available/allowed memory. This can lead to an unexpected ENOMEM/EFAULT > >resp. SIGSEGV when memory is accounted." > > > > Fair enough, thanks. :-) > > >I think this is also worth pushing to the stable tree (it goes back to > >2.6.27) > > > > Yup, I will Cc Greg in next version. Ccing Greg doesn't help. All that is required is: Cc: stable@xxxxxxxxxxxxxxx # 2.6.27+ > >> Testcase: > >> boot: hugepagesz=1G hugepages=1 > >> before patch: > >> egrep 'CommitLimit' /proc/meminfo > >> CommitLimit: 55434168 kB > >> after patch: > >> egrep 'CommitLimit' /proc/meminfo > >> CommitLimit: 54909880 kB > > > >This gives some more confusion to a reader because there is only > >something like 500M difference here without any explanation. > > > > the default overcommit ratio is 50. And that part was missing in the description... [...] -- 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>