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SubjectRe: [PATCH] cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available
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On 8/1/2019 9:06 AM, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> The downside of guest side polling is that polling is performed even
> with other runnable tasks in the host. However, even if poll in kvm
> can aware whether or not other runnable tasks in the same pCPU, it
> can still incur extra overhead in over-subscribe scenario. Now we can
> just enable guest polling when dedicated pCPUs are available.
>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>

Paolo, Marcelo, any comments?


> ---
> drivers/cpuidle/cpuidle-haltpoll.c | 3 ++-
> drivers/cpuidle/governors/haltpoll.c | 2 +-
> 2 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
> index 9ac093d..7aee38a 100644
> --- a/drivers/cpuidle/cpuidle-haltpoll.c
> +++ b/drivers/cpuidle/cpuidle-haltpoll.c
> @@ -53,7 +53,8 @@ static int __init haltpoll_init(void)
>
> cpuidle_poll_state_init(drv);
>
> - if (!kvm_para_available())
> + if (!kvm_para_available() ||
> + !kvm_para_has_hint(KVM_HINTS_REALTIME))
> return 0;
>
> ret = cpuidle_register(&haltpoll_driver, NULL);
> diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governors/haltpoll.c
> index 797477b..685c7007 100644
> --- a/drivers/cpuidle/governors/haltpoll.c
> +++ b/drivers/cpuidle/governors/haltpoll.c
> @@ -141,7 +141,7 @@ static struct cpuidle_governor haltpoll_governor = {
>
> static int __init init_haltpoll(void)
> {
> - if (kvm_para_available())
> + if (kvm_para_available() && kvm_para_has_hint(KVM_HINTS_REALTIME))
> return cpuidle_register_governor(&haltpoll_governor);
>
> return 0;


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