linux-kernel - Re: [PATCH 0/15] KVM: optimize for MMIO handled

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Date:	Wed, 8 Jun 2011 12:47:40 +0900
From:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH 0/15] KVM: optimize for MMIO handled

On Wed, 08 Jun 2011 11:32:12 +0800
Xiao Guangrong <xiaoguangrong@...fujitsu.com> wrote:

> On 06/08/2011 11:25 AM, Xiao Guangrong wrote:
> > On 06/08/2011 11:11 AM, Takuya Yoshikawa wrote:
> >> On Tue, 07 Jun 2011 20:58:06 +0800
> >> Xiao Guangrong <xiaoguangrong@...fujitsu.com> wrote:
> >>
> >>> The performance test result:
> >>>
> >>> Netperf (TCP_RR):
> >>> ===========================
> >>> ept is enabled:
> >>>
> >>>       Before         After
> >>> 1st   709.58         734.60
> >>> 2nd   715.40         723.75
> >>> 3rd   713.45         724.22
> >>>
> >>> ept=0 bypass_guest_pf=0:
> >>>
> >>>       Before         After
> >>> 1st   706.10         709.63
> >>> 2nd   709.38         715.80
> >>> 3rd   695.90         710.70
> >>>
> >>
> >> In what condition, does TCP_RR perform so bad?
> >>
> >> On 1Gbps network, directly connecting two Intel servers,
> >> I got 20 times better result before.
> >>
> >> Even when I used a KVM guest as the netperf client,
> >> I got more than 10 times better result.
> >>
> > 
> > Um, which case did you test? ept = 1 or ept=0 bypass_guest_pf=0 or both?
> > 

ept = 1 only.

> >> Could you tell me a bit more details of your test?
> >>
> > 
> > Sure, KVM guest is the client, and it uses e1000 NIC, and uses NAT
> > network connect to the netperf server, the bandwidth of our network
> > is 100M.
> > 

I see the reason, thank you!

I used virtio-net and you used e1000.
You are using e1000 to see the MMIO performance change, right?

  Takuya

> 
> And this is my test script:
> 
> #!/bin/sh
> 
> echo 3 > /proc/sys/vm/drop_caches
> ./netperf -H $HOST_NAME -p $PORT -t TCP_RR -l 60
> 
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