[PATCH 0/3] KVM: Dynamic halt_poll_ns

[Wanpeng Li]

There is a downside of halt_poll_ns since poll is still happen for idle 
VCPU which can waste cpu usage. This patchset add the ability to adjust 
halt_poll_ns dynamically, grows halt_poll_ns if an interrupt arrives and 
shrinks halt_poll_ns when idle VCPU is detected.

There are two new kernel parameters for changing the halt_poll_ns:
halt_poll_ns_grow and halt_poll_ns_shrink. halt_poll_ns_grow affects 
halt_poll_ns when an interrupt arrives and halt_poll_ns_shrink
does it when idle VCPU is detected. 

  halt_poll_ns_shrink/ |
  halt_poll_ns_grow    | interrupt arrives    | idle VCPU is detected
  ---------------------+----------------------+-------------------
  < 1                  |  = halt_poll_ns      |  = 0 
  < halt_poll_ns       | *= halt_poll_ns_grow | /= halt_poll_ns_shrink
  otherwise            | += halt_poll_ns_grow | -= halt_poll_ns_shrink

A third new parameter, halt_poll_ns_max, controls the maximal halt_poll_ns;
it is internally rounded down to a closest multiple of halt_poll_ns_grow.

Wanpeng Li (3):
  KVM: make halt_poll_ns per-VCPU
  KVM: dynamise halt_poll_ns adjustment 
  KVM: trace kvm_halt_poll_ns grow/shrink 

 include/linux/kvm_host.h   |  1 +
 include/trace/events/kvm.h | 30 ++++++++++++++++
 virt/kvm/kvm_main.c        | 90 +++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 120 insertions(+), 1 deletion(-)

-- 
1.9.1

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