On Fri, 2014-05-23 at 11:53 +0200, Alexander Graf wrote: > On 23.05.14 10:15, Michael Neuling wrote: > > This patch series implements split core mode on POWER8. This enables up to 4 > > subcores per core which can each independently run guests (per guest SPRs like > > SDR1, LPIDR etc are replicated per subcore). Lots more documentation on this > > feature in the code and commit messages. > > > > Most of this code is in the powernv platform but there's a couple of KVM > > specific patches too. > > > > Patch series authored by mpe and me with a few bug fixes from others. > > > > v2: > > There are some minor updates based on comments and I've added the Acks by > > Paulus and Alex for the KVM code. > > I don't see changelogs inside the individual patches. Please make sure > to always mention what changed from one version to the next in a > particular patch, so that I have the chance to check whether that change > was good :). Sure, that was a bit sloppy Only the last patch was the only one that changed. I changed the sysfs file from 600 permissions to 644 so that users can read it more easily as requested by Joel. The other change was to fix the possibility of a race when coming out of nap and checking if we need to split. This fix was form paulus' (worked offline). > Also, is there any performance penalty associated with split core mode? > If not, could we just always default to split-by-4 on POWER8 bare metal? Yeah, there is a performance hit . When you are split (ie subcores_per_core = 2 or 4), the core is stuck in SMT8 mode. So if you only have 1 thread active (others napped), you won't get the benefit of ST mode in the core (more register renames per HW thread, more FXUs, more FPUs etc). Mikey -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
