On Tue, Nov 06, 2012 at 01:27:37PM -0800, Andrew Morton wrote: > On Mon, 5 Nov 2012 15:24:08 -0800 > Andi Kleen <andi@xxxxxxxxxxxxxx> wrote: > > > From: Andi Kleen <ak@xxxxxxxxxxxxxxx> > > > > There was some desire in large applications using MAP_HUGETLB/SHM_HUGETLB > > to use 1GB huge pages on some mappings, and stay with 2MB on others. This > > is useful together with NUMA policy: use 2MB interleaving on some mappings, > > but 1GB on local mappings. > > > > This patch extends the IPC/SHM syscall interfaces slightly to allow specifying > > the page size. > > > > It borrows some upper bits in the existing flag arguments and allows encoding > > the log of the desired page size in addition to the *_HUGETLB flag. > > When 0 is specified the default size is used, this makes the change fully > > compatible. > > > > Extending the internal hugetlb code to handle this is straight forward. Instead > > of a single mount it just keeps an array of them and selects the right > > mount based on the specified page size. When no page size is specified > > it uses the mount of the default page size. > > > > The change is not visible in /proc/mounts because internal mounts > > don't appear there. It also has very little overhead: the additional > > mounts just consume a super block, but not more memory when not used. > > > > I also exported the new flags to the user headers > > (they were previously under __KERNEL__). Right now only symbols > > for x86 and some other architecture for 1GB and 2MB are defined. > > The interface should already work for all other architectures > > though. Only architectures that define multiple hugetlb sizes > > actually need it (that is currently x86, tile, powerpc). However > > tile and powerpc have user configurable hugetlb sizes, so it's > > not easy to add defines. A program on those architectures would > > need to query sysfs and use the appropiate log2. > > I can't say the userspace interface is a thing of beauty, but I guess > we'll live. Thanks. > > Did you have a test app? If so, can we get it into > tools/testing/selftests and point the arch maintainers at it? Yes I do. I'll send a patch separately. However you have to run with the right options and it may be slightly x86 specific. > unregister_filesystem(&hugetlbfs_fs_type); > bdi_destroy(&hugetlbfs_backing_dev_info); > > (we're not supposed to split strings like that, but screw 'em!) Thanks I assume you handle that. -Andi -- ak@xxxxxxxxxxxxxxx -- Speaking for myself only. -- 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>