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From: Rik van Riel <riel@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>,
	linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Cc: Luiz Capitulino <lcapitulino@redhat.com>,
	Steven Rostedt <srostedt@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq
Date: Wed, 14 Jan 2015 13:22:43 -0500	[thread overview]
Message-ID: <54B6B3F3.2000908@redhat.com> (raw)
In-Reply-To: <20150114171459.593877145@redhat.com>

On 01/14/2015 12:12 PM, Marcelo Tosatti wrote:
> The problem:
> 
> On -RT, an emulated LAPIC timer instances has the following path:
> 
> 1) hard interrupt
> 2) ksoftirqd is scheduled
> 3) ksoftirqd wakes up vcpu thread
> 4) vcpu thread is scheduled
> 
> This extra context switch introduces unnecessary latency in the 
> LAPIC path for a KVM guest.

> This patch reduces the average latency in my tests from 14us to 11us.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Acked-by: Rik van Riel <riel@redhat.com>


  reply	other threads:[~2015-01-14 18:22 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-14 17:12 [patch -rt 0/2] use simple waitqueue for kvm vcpu waitqueue (v3) Marcelo Tosatti
2015-01-14 17:12 ` [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq Marcelo Tosatti
2015-01-14 18:22   ` Rik van Riel [this message]
2015-01-16 16:48   ` Steven Rostedt
2015-01-16 16:56     ` Steven Rostedt
2015-01-17  7:57     ` Peter Zijlstra
2015-01-19 14:41     ` Marcelo Tosatti
2015-01-20  5:46       ` Paul Mackerras
2015-01-20 18:16         ` Steven Rostedt
2015-01-21 15:07           ` Peter Zijlstra
2015-02-17 17:44             ` Sebastian Andrzej Siewior
2015-02-18 14:03               ` Peter Zijlstra
2015-02-25 21:02                 ` Sebastian Andrzej Siewior
2015-08-07 10:57                   ` Peter Zijlstra
2015-08-07 11:14                     ` Peter Zijlstra
2015-08-07 11:14                       ` Peter Zijlstra
2015-08-07 16:41                       ` Christoph Hellwig
2015-08-07 16:45                         ` Peter Zijlstra
2015-08-09  6:39                           ` Christoph Hellwig
2015-08-17 20:31                       ` Thomas Gleixner
2015-02-27  0:23               ` Marcelo Tosatti
2015-03-05  1:09                 ` Marcelo Tosatti
2015-03-05  1:09                   ` Marcelo Tosatti
2015-03-05  7:42                   ` Sebastian Andrzej Siewior
2015-03-06 13:54   ` Sebastian Andrzej Siewior
2015-01-14 17:12 ` [patch -rt 2/2] KVM: lapic: mark LAPIC timer handler as irqsafe Marcelo Tosatti
2015-01-14 18:23   ` Rik van Riel
2015-01-14 17:35 ` [patch -rt 0/2] use simple waitqueue for kvm vcpu waitqueue (v3) Paolo Bonzini
  -- strict thread matches above, loose matches on Subject: below --
2015-04-08 23:33 [patch -rt 0/2] use simple waitqueue for kvm vcpu waitqueue (v5) Marcelo Tosatti
2015-04-08 23:33 ` [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq Marcelo Tosatti
2015-01-21 20:36 [patch -rt 0/2] use simple waitqueue for kvm vcpu waitqueue (v4) Marcelo Tosatti
2015-01-21 20:36 ` [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq Marcelo Tosatti
2014-11-25 17:21 [patch -rt 0/2] use simple waitqueue for kvm vcpu waitqueue (v2) Marcelo Tosatti
2014-11-25 17:21 ` [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq Marcelo Tosatti
2014-11-25 18:57   ` Rik van Riel
2014-11-25 19:08     ` Rik van Riel
2014-11-25 19:30     ` Marcelo Tosatti
2014-11-25 20:23     ` Thomas Gleixner
2014-11-25 16:45 [patch -rt 0/2] use simple waitqueue for kvm vcpu waitqueue Marcelo Tosatti
2014-11-25 16:45 ` [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq Marcelo Tosatti

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