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From: Paolo Bonzini <pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: kvm@vger.kernel.org, Luiz Capitulino <lcapitulino@redhat.com>,
	Rik van Riel <riel@redhat.com>, Radim Krcmar <rkrcmar@redhat.com>
Subject: Re: [patch 2/2] KVM: x86: add option to advance tscdeadline hrtimer expiration
Date: Thu, 11 Dec 2014 19:58:47 +0100	[thread overview]
Message-ID: <5489E967.3060301@redhat.com> (raw)
In-Reply-To: <20141211030753.GA6358@amt.cnet>



On 11/12/2014 04:07, Marcelo Tosatti wrote:
>> > So, on APICv, if the interrupt is in PIR but it has bits 7:4 <=
>> > PPR[7:4], you have a problem. :(  There is no APICv hook that lets you
>> > get a vmexit when the PPR becomes low enough.
> Well, you simply exit earlier and busy spin for VM-exit
> time.

Okay, given how small the jitter is in your plots, a small busy wait is
not the end of the world even if it caused a very short priority
inversion.  Can you add a tracepoint that triggers when you do the busy
wait, and possibly a kvm stat that counts good (no busy wait) vs. bad
(busy wait) invocations of wait_lapic_expire?

Thanks,

Paolo

  reply	other threads:[~2014-12-11 18:58 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-10 20:57 [patch 0/2] KVM: add option to advance tscdeadline hrtimer expiration (v3) Marcelo Tosatti
2014-12-10 20:57 ` [patch 1/2] KVM: x86: add method to test PIR bitmap vector Marcelo Tosatti
2014-12-10 20:57 ` [patch 2/2] KVM: x86: add option to advance tscdeadline hrtimer expiration Marcelo Tosatti
2014-12-10 23:37   ` Paolo Bonzini
2014-12-11  3:07     ` Marcelo Tosatti
2014-12-11 18:58       ` Paolo Bonzini [this message]
2014-12-11 20:48       ` Andy Lutomirski
2014-12-11 20:58         ` Marcelo Tosatti
2014-12-11 21:07           ` Andy Lutomirski
2014-12-11 21:37             ` Rik van Riel
2014-12-11 21:10         ` Paolo Bonzini
2014-12-11 21:16           ` Andy Lutomirski
2014-12-11 21:27             ` Marcelo Tosatti
2014-12-11 21:29               ` Marcelo Tosatti
2014-12-12 18:35   ` Radim Krcmar
  -- strict thread matches above, loose matches on Subject: below --
2014-12-10 17:06 [patch 0/2] KVM: add option to advance tscdeadline hrtimer expiration (v2) Marcelo Tosatti
2014-12-10 17:06 ` [patch 2/2] KVM: x86: add option to advance tscdeadline hrtimer expiration Marcelo Tosatti
2014-12-10 17:11   ` Rik van Riel
2014-12-10 16:53 [patch 0/2] KVM: " Marcelo.Tosatti
2014-12-10 16:53 ` [patch 2/2] KVM: x86: " Marcelo.Tosatti
2014-12-10 17:08   ` Paolo Bonzini
2014-12-10 17:34     ` Marcelo Tosatti
2014-12-10 17:53       ` Paolo Bonzini

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