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From: Paolo Bonzini <pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: kvm-devel <kvm@vger.kernel.org>,
	"Radim KrÄ?máÅ?" <rkrcmar@redhat.com>,
	"Andrea Arcangeli" <aarcange@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Wanpeng Li" <kernellwp@gmail.com>,
	"Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>,
	"Raslan KarimAllah" <karahmed@amazon.de>,
	"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
	"Ankur Arora" <ankur.a.arora@oracle.com>,
	"Christian Borntraeger" <borntraeger@de.ibm.com>,
	"Linux PM" <linux-pm@vger.kernel.org>
Subject: Re: [patch 0/3] cpuidle-haltpoll driver (v2)
Date: Fri, 7 Jun 2019 20:22:35 +0200
Message-ID: <9c3853cc-d920-03e8-245c-86c33b280c80@redhat.com> (raw)
In-Reply-To: <20190607171645.GA28275@amt.cnet>

On 07/06/19 19:16, Marcelo Tosatti wrote:
> There is no "target residency" concept in the virtualized use-case 
> (which is what poll_state.c uses to calculate the poll time).

Actually there is: it is the cost of a vmexit, and it be calibrated with
a very short CPUID loop (e.g. run 100 CPUID instructions and take the
smallest TSC interval---it should take less than 50 microseconds, and
less than a millisecond even on nested virt).

I think it would make sense to improve poll_state.c to use an adaptive
algorithm similar to the one you implemented, which includes optionally
allowing to poll for an interval larger than the target residency.

Paolo

  reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190603225242.289109849@amt.cnet>
2019-06-07  9:49 ` Rafael J. Wysocki
2019-06-07 17:16   ` Marcelo Tosatti
2019-06-07 18:22     ` Paolo Bonzini [this message]
2019-06-07 21:38       ` Marcelo Tosatti
2019-06-10 14:59   ` Marcelo Tosatti
2019-06-10 22:03     ` Rafael J. Wysocki
2019-06-11 14:26       ` Marcelo Tosatti
2019-06-11 21:24         ` Rafael J. Wysocki
2019-06-17 15:57           ` Peter Zijlstra
     [not found] ` <20190603225254.212931277@amt.cnet>
2019-06-07  9:54   ` [patch 1/3] drivers/cpuidle: add cpuidle-haltpoll driver Rafael J. Wysocki

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