Re: [PATCH 0/6] kvm: powerpc halt polling updates

On Fri, Oct 14, 2016 at 11:53:18AM +1100, Suraj Jitindar Singh wrote:

This patch series makes some updates and bug fixes to the powerpc kvm-hv
halt polling code.

The first two patches are concerned with exporting the generic kvm module
parameter variables and accessing these from the powerpc specific code.

The third patch fixes a bug where changing the global max halt polling
interval module parameter can sometimes have no effect.

The fourth patch decreases the default global max halt polling interval
to something more sensible.

The fifth patch contains generic fixups with no functional effect.

The last patch adds halt polling documentation.

Suraj Jitindar Singh (6):
  kvm: export kvm module parameter variables
  powerpc/kvm: Use generic kvm module parameters in kvm-hv
  powerpc/kvm: Add check for module parameter halt_poll_ns
  powerpc/kvm: Decrease the powerpc default halt poll max value
  powerpc/kvm: Comment style and print format fixups
  doc/kvm: Add halt polling documentation

 Documentation/virtual/kvm/00-INDEX         |   2 +
 Documentation/virtual/kvm/halt-polling.txt | 127 +++++++++++++++++++++++++++++
 arch/powerpc/include/asm/kvm_host.h        |   2 +-
 arch/powerpc/kvm/book3s_hv.c               |  33 ++------
 arch/powerpc/kvm/trace_hv.h                |   2 +-
 include/linux/kvm_host.h                   |   4 +
 virt/kvm/kvm_main.c                        |   9 +-
 7 files changed, 149 insertions(+), 30 deletions(-)
 create mode 100644 Documentation/virtual/kvm/halt-polling.txt

-- 
2.5.5

Hi Suraj,

I've given this set a quick test and it seems to work fine. I used a repetitive
wakeup, using a nanosleep loop in guest userspace (with real time prio), and I
was able to cause halt polling to switch on and off as I adjusted halt_poll_ns.
I think the new default value is much better: halt polling started (e.g. CPU
utilization rose to 100%) once CPU utilization had already risen to about 75%.

Cheers,
Sam.

Tested-by: Sam Bobroff <redacted>