linux-kernel - Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM virtio-net.

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Message-ID: <1281497282.3391.31.camel@localhost.localdomain>
Date:	Tue, 10 Aug 2010 20:28:02 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	xiaohui.xin@...el.com, netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com, mingo@...e.hu,
	davem@...emloft.net, herbert@...dor.hengli.com.au,
	jdike@...ux.intel.com
Subject: Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM
 virtio-net.

Hello Avi,

On Mon, 2010-08-02 at 19:32 +0300, Avi Kivity wrote:
> When are you seeing gup_fast() fall back to gup()?  It should be at
> most 
> once per page (when a guest starts up none of its pages are mapped,
> it 
> faults them in on demand). 

netperf/netserver latency results are pretty good for message size
between 1 bytes and 512 bytes when I have 64 bytes small copy.

However if I don't have any small copy , the ping RTT time is
unreasonable huge. Since we think it's better to have small message with
copy, so there will be no issue.

Thanks
Shirley

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