linux-kernel - Re: [PATCH v5] KVM: halt-polling: poll for the upcoming fire timers

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Date:	Fri, 27 May 2016 17:14:57 -0700
From:	yunhong jiang <yunhong.jiang@...ux.intel.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, Wanpeng Li <wanpeng.li@...mail.com>,
	Radim Krčmář <rkrcmar@...hat.com>,
	David Matlack <dmatlack@...gle.com>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Yang Zhang <yang.zhang.wz@...il.com>
Subject: Re: [PATCH v5] KVM: halt-polling: poll for the upcoming fire timers

On Fri, 27 May 2016 11:49:26 +0200
Paolo Bonzini <pbonzini@...hat.com> wrote:

> 
> 
> On 26/05/2016 22:33, yunhong jiang wrote:
> > On Thu, 26 May 2016 12:26:27 +0200
> > Paolo Bonzini <pbonzini@...hat.com> wrote:
> > 
> >>
> >>
> >> On 25/05/2016 04:47, Wanpeng Li wrote:
> >>> From: Wanpeng Li <wanpeng.li@...mail.com>
> >>>
> >>> If an emulated lapic timer will fire soon(in the scope of 10us the
> >>> base of dynamic halt-polling, lower-end of message passing
> >>> workload latency TCP_RR's poll time < 10us) we can treat it as a
> >>> short halt, and poll to wait it fire, the fire callback
> >>> apic_timer_fn() will set KVM_REQ_PENDING_TIMER, and this flag
> >>> will be check during busy poll. This can avoid context switch
> >>> overhead and the latency which we wake up vCPU.
> >>
> >> As discussed on IRC, I would like to understand why the adaptive
> > 
> > Glad to know the IRC channel. Is #kvm channel on freenode the IRC
> > you are talking about?
> 
> No, it's #qemu on irc.oftc.net

Thanks for the information.

--jyh

> 
> Thanks,
> 
> Paolo