On Mon, Apr 12, 2010 at 07:26:15PM +1000, Nick Piggin wrote: > But if it is possible for KVM to use libhugetlb with just a bit of > support from the kernel, then it goes some way to reducing the > need for transparent hugepages. KVM has full hugetlbfs support for a long time. There's some people using it, and it remains a must-have for 1G pages, but it's not manageable that way in the cloud. It's ok for a special instance only. Right now all my VM by default are running on hugepages now without changing a single bit (with a few liner patch to qemu to add a alignment because the gfn bits in the number range HPAGE_PMD_SHIFT..PAGE_SHIFT have to be a match to the host pfn bits for NPT shadows to go pmd_huge). For qemu to run on hugepages not even the alignment is needed (but it's better to align there too, to be sure the guest kernel that lives hugepages as it's usually mapped in the first mbyte). This is the single change I had to apply to KVM for it to take advantage of transparent hugepages because it was already working fine with hugetlbfs: http://git.kernel.org/?p=linux/kernel/git/andrea/aa.git;a=commit;h=d249c189870896b3f275987b70702d2b8c7705d4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>