Hi Laszlo, On Thu, Apr 21, 2016 at 11:58:07PM +0200, Laszlo Ersek wrote: > On 04/21/16 18:23, Christoffer Dall wrote: > > Hi, > > > > Commit 9fac18f (oslib: allocate PROT_NONE pages on top of RAM, > > 2015-09-10) had the unfortunate side effect that memory slots registered > > with KVM no longer contain a userspace address that is aligned to a 2M > > boundary, causing the use of THP to fail in the kernel. > > > > I fail to see where in the QEMU code we should be asking for a 2M > > alignment of our memory region. Can someone help pointing me to the > > right place to fix this or suggest a patch? > > > > This causes a performance regssion of hackbench on KVM/ARM of about 62% > > compared to the workload running with THP. > > > > We have verified that this is indeed the cause of the failure by adding > > various prints to QEMU and the kernel, but unfortunatley my QEMU > > knowledge is not sufficient for me to fix it myself. > > > > Any help would be much appreciated! > > Can you please test the attached series? > > (Note that I'm only interested in solving this problem as a productive > distraction, so if the patches don't work, or require a lot of massaging > for merging, I'll just drop them (or, preferably, give them to someone > else).) >
I like your procrastination methods! Unfortunately this fix wasn't the right one either. -Christoffer