lkml.org 
[lkml]   [2019]   [Sep]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v2] cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available
From
Date
On 8/29/2019 10:49 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.
>
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>

As stated before, I'm going to queue up this change for 5.4, with the
Paolo's ACK.

BTW, in the future please CC power management changes to
linux-pm@vger.kernel.org for easier handling.

> --
> v1 -> v2:
> * export kvm_arch_para_hints to fix haltpoll driver build as module error
> * just disable haltpoll driver instead of both driver and governor
> since KVM_HINTS_REALTIME is not defined in other arches, and governor
> doesn't depend on x86, to fix the warning on powerpc
>
> arch/x86/kernel/kvm.c | 1 +
> drivers/cpuidle/cpuidle-haltpoll.c | 3 ++-
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index f48401b..68463c1 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -711,6 +711,7 @@ unsigned int kvm_arch_para_hints(void)
> {
> return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);
> }
> +EXPORT_SYMBOL_GPL(kvm_arch_para_hints);
>
> static uint32_t __init kvm_detect(void)
> {
> 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);


\
 
 \ /
  Last update: 2019-09-04 11:48    [W:0.203 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site