linux-kernel - [PATCH v2 0/3] KVM: Dynamic halt_poll

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Date:	Tue, 25 Aug 2015 14:35:16 +0800
From:	Wanpeng Li <wanpeng.li@...mail.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	David Matlack <dmatlack@...gle.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Wanpeng Li <wanpeng.li@...mail.com>
Subject: [PATCH v2 0/3] KVM: Dynamic halt_poll_ns 

v1 -> v2:
 * change kvm_vcpu_block to read halt_poll_ns from the vcpu instead of 
   the module parameter
 * use the shrink/grow matrix which is suggested by David
 * set halt_poll_ns_max to 2ms

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. 

There are two new kernel parameters for changing the halt_poll_ns:
halt_poll_ns_grow and 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. The shrink/grow 
matrix is suggested by David: 

if (poll successfully for interrupt): stay the same
  else if (length of kvm_vcpu_block is longer than halt_poll_ns_max): shrink
  else if (length of kvm_vcpu_block is less than halt_poll_ns_max): grow

  halt_poll_ns_shrink/ |
  halt_poll_ns_grow    | grow halt_poll_ns    | shrink halt_poll_ns 
  ---------------------+----------------------+-------------------
  < 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

Wanpeng Li (3):
  KVM: make halt_poll_ns per-VCPU
  KVM: dynamic 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        | 78 ++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 106 insertions(+), 3 deletions(-)

-- 
1.9.1

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