This patch series provides a way to use more of the capacity of each processor core when running guests configured with threads=1, 2 or 4 on a POWER8 host with HV KVM, without having to change the static micro-threading (the official name for split-core) mode for the whole machine. The problem with setting the machine to static 2-way or 4-way micro-threading mode is that (a) then you can't run guests with threads=8 and (b) selecting the right mode can be tricky and requires knowledge of what guests you will be running. Instead, with these two patches, we can now run more than one virtual core (vcore) on a given physical core if possible, and if that means we need to switch the core to 2-way or 4-way micro-threading mode, then we do that on entry to the guests and switch back to whole-core mode on exit (and we only switch the one core, not the whole machine). The core mode switching is only done if the machine is in static whole-core mode. All of this only comes into effect when a core is over-committed. When the machine is lightly loaded everything operates the same with these patches as without. Only when some core has a vcore that is able to run while there is also another vcore that was wanting to run on that core but got preempted does the logic kick in to try to run both vcores at once. Paul. --- arch/powerpc/include/asm/kvm_book3s_asm.h | 20 + arch/powerpc/include/asm/kvm_host.h | 22 +- arch/powerpc/kernel/asm-offsets.c | 9 + arch/powerpc/kvm/book3s_hv.c | 648 ++++++++++++++++++++++++++---- arch/powerpc/kvm/book3s_hv_builtin.c | 32 +- arch/powerpc/kvm/book3s_hv_rm_xics.c | 4 +- arch/powerpc/kvm/book3s_hv_rmhandlers.S | 111 ++++- 7 files changed, 740 insertions(+), 106 deletions(-) -- 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
