On Sat, Oct 20, 2012 at 12:48 AM, 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. > > v2: Port to new tree. Fix unmount. > v3: Ported to latest tree. > v4: Ported to latest tree. Minor changes for review feedback. Updated > description. > v5: Remove unnecessary prototypes to fix merge error (Hillf Danton) > v6: Rebased. Fix some unlikely error paths (Hillf Danton) > Acked-by: Rik van Riel <riel@xxxxxxxxxx> > Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Cc: Hillf Danton <dhillf@xxxxxxxxx> > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> > --- Thanks:) Acked-by: Hillf Danton <dhillf@xxxxxxxxx> -- 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>