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Re: [PATCH 2/2] x86/idle: use dynamic halt poll

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On 22/06/2017 13:22, root wrote:
>  ==============================================================
>  
> +poll_grow: (X86 only)
> +
> +This parameter is multiplied in the grow_poll_ns() to increase the poll time.
> +By default, the values is 2.
> +
> +==============================================================
> +poll_shrink: (X86 only)
> +
> +This parameter is divided in the shrink_poll_ns() to reduce the poll time.
> +By default, the values is 2.

Even before starting the debate on whether this is a good idea or a bad
idea, KVM reduces the polling value to the minimum (10 us) by default
when polling fails.  Also, it shouldn't be bound to
CONFIG_HYPERVISOR_GUEST, since there's nothing specific to virtual
machines here.

Regarding the good/bad idea part, KVM's polling is made much more
acceptable by single_task_running().  At least you need to integrate it
with paravirtualization.  If the VM is scheduled out, you shrink the
polling period.  There is already vcpu_is_preempted for this, it is used
by mutexes.

Paolo

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[PATCH 0/2] x86/idle: add halt poll support root <yang.zhang.wz@gmail.com> - 2017-06-22 13:30 +0200
  [PATCH 1/2] x86/idle: add halt poll for halt idle root <yang.zhang.wz@gmail.com> - 2017-06-22 13:30 +0200
    Re: [PATCH 1/2] x86/idle: add halt poll for halt idle Thomas Gleixner <tglx@linutronix.de> - 2017-06-22 16:30 +0200
      Re: [PATCH 1/2] x86/idle: add halt poll for halt idle Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-23 06:10 +0200
  [PATCH 2/2] x86/idle: use dynamic halt poll root <yang.zhang.wz@gmail.com> - 2017-06-22 13:30 +0200
    Re: [PATCH 2/2] x86/idle: use dynamic halt poll Paolo Bonzini <pbonzini@redhat.com> - 2017-06-22 14:00 +0200
      Re: [PATCH 2/2] x86/idle: use dynamic halt poll Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-23 06:00 +0200
        Re: [PATCH 2/2] x86/idle: use dynamic halt poll Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-27 13:30 +0200
          Re: [PATCH 2/2] x86/idle: use dynamic halt poll Paolo Bonzini <pbonzini@redhat.com> - 2017-06-27 14:10 +0200
            Re: [PATCH 2/2] x86/idle: use dynamic halt poll Wanpeng Li <kernellwp@gmail.com> - 2017-06-27 14:30 +0200
              Re: [PATCH 2/2] x86/idle: use dynamic halt poll Paolo Bonzini <pbonzini@redhat.com> - 2017-06-27 14:30 +0200
                Re: [PATCH 2/2] x86/idle: use dynamic halt poll Radim Krčmář <rkrcmar@redhat.com> - 2017-06-27 15:50 +0200
                Re: [PATCH 2/2] x86/idle: use dynamic halt poll Paolo Bonzini <pbonzini@redhat.com> - 2017-06-27 16:00 +0200
                Re: [PATCH 2/2] x86/idle: use dynamic halt poll Paolo Bonzini <pbonzini@redhat.com> - 2017-06-27 16:30 +0200
                Re: [PATCH 2/2] x86/idle: use dynamic halt poll Radim Krčmář <rkrcmar@redhat.com> - 2017-06-27 16:30 +0200
                Re: [PATCH 2/2] x86/idle: use dynamic halt poll Yang Zhang <yang.zhang.wz@gmail.com> - 2017-07-03 11:30 +0200
                Re: [PATCH 2/2] x86/idle: use dynamic halt poll Thomas Gleixner <tglx@linutronix.de> - 2017-07-03 12:10 +0200
    Re: [PATCH 2/2] x86/idle: use dynamic halt poll Thomas Gleixner <tglx@linutronix.de> - 2017-06-22 16:40 +0200
      Re: [PATCH 2/2] x86/idle: use dynamic halt poll Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-23 06:10 +0200
    Re: [PATCH 2/2] x86/idle: use dynamic halt poll kbuild test robot <lkp@intel.com> - 2017-06-23 00:50 +0200
  Re: [PATCH 0/2] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-22 13:40 +0200
  Re: [PATCH 0/2] x86/idle: add halt poll support Wanpeng Li <kernellwp@gmail.com> - 2017-06-22 14:00 +0200
    Re: [PATCH 0/2] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-23 06:10 +0200
      Re: [PATCH 0/2] x86/idle: add halt poll support Wanpeng Li <kernellwp@gmail.com> - 2017-06-23 06:40 +0200
        Re: [PATCH 0/2] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-06-23 08:50 +0200
          Re: [PATCH 0/2] x86/idle: add halt poll support Radim Krčmář <rkrcmar@redhat.com> - 2017-06-27 16:10 +0200

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