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

[Sam Bobroff]

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 <sam.bobroff at au1.ibm.com>