On 22 April 2016 at 12:12, Christoffer Dall <christoffer.d...@linaro.org> wrote: > For KVM to use Transparent Huge Pages (THP) we have to ensure that the > alignment of the userspace address of the KVM memory slot and the IPA > that the guest sees for a memory region have the same offset from the 2M > huge page size boundary. > > One way to achieve this is to always align the IPA region at a 2M > boundary and ensure that the mmap alignment is also at 2M. > > Unfortunately, we were only doing this for __arm__, not for __aarch64__, > so add this simply condition. > > This fixes a performance regression using KVM/ARM on AArch64 platforms > that showed a performance penalty of more than 50%, introduced by the > following commit: > > 9fac18f (oslib: allocate PROT_NONE pages on top of RAM, 2015-09-10) > > We were only lucky before the above commit, because we were allocating > large regions and naturally getting a 2M alignment on those allocations > then. > > Reported-by: Shih-Wei Li <shih...@cs.columbia.edu> > Signed-off-by: Christoffer Dall <christoffer.d...@linaro.org> > --- > The first version of this patch was accidentally made against the v2.5.0 > release instead of master, so this is a rebased version.
Thanks; applied to master (with the long line wrapped). -- PMM
