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From: Ingo Molnar <mingo@elte.hu>
To: Avi Kivity <avi@qumranet.com>
Cc: kvm-devel <kvm-devel@lists.sourceforge.net>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: kvm & dyntick
Date: Fri, 12 Jan 2007 11:19:31 +0100	[thread overview]
Message-ID: <20070112101931.GA11635@elte.hu> (raw)
In-Reply-To: <20070112062006.GA32714@elte.hu>


* Ingo Molnar <mingo@elte.hu> wrote:

> > dyntick-enabled guest:
> > - reduce the load on the host when the guest is idling
> >   (currently an idle guest consumes a few percent cpu)
> 
> yeah. KVM under -rt already works with dynticks enabled on both the 
> host and the guest. (but it's more optimal to use a dedicated 
> hypercall to set the next guest-interrupt)

using the dynticks code from the -rt kernel makes the overhead of an 
idle guest go down by a factor of 10-15:

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
 2556 mingo     15   0  598m 159m 157m R  1.5  8.0   0:26.20 qemu

( for this to work on my system i have added a 'hyper' clocksource 
  hypercall API for KVM guests to use - this is needed instead of the 
  running-to-slowly TSC. )

	Ingo

  reply	other threads:[~2007-01-12 10:58 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-11 16:08 Avi Kivity
2007-01-12  5:34 ` Rik van Riel
2007-01-12  6:20 ` Ingo Molnar
2007-01-12 10:19   ` Ingo Molnar [this message]
2007-01-12 17:04     ` Avi Kivity
2007-01-14  8:39       ` Ingo Molnar
2007-01-12 23:25     ` [kvm-devel] " Dor Laor
2007-01-12 23:39       ` Thomas Gleixner
2007-01-14  8:51       ` Ingo Molnar

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