From mboxrd@z Thu Jan  1 00:00:00 1970
From: Shirley Ma <mashirle@us.ibm.com>
Subject: Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM
 virtio-net.
Date: Fri, 30 Jul 2010 08:46:11 -0700
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Cc: xiaohui.xin@intel.com, netdev@vger.kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, mst@redhat.com, mingo@elte.hu,
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To: Avi Kivity <avi@redhat.com>
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Hello Avi,

On Fri, 2010-07-30 at 08:02 +0300, Avi Kivity wrote:
> get_user_pages() is indeed slow.  But what about
> get_user_pages_fast()?
> 
> Note that when the page is first touched, get_user_pages_fast() falls 
> back to get_user_pages(), so the latency needs to be measured after 
> quite a bit of warm-up. 

Yes, I used get_user_pages_fast, however if falled back to
get_user_pages() when the apps doesn't allocate buffer on the same page.
If I run a single ping, the RTT is extremely high, but when running
multiple pings, the RTT time reduce significantly, but still it is not
as fast as copy from my initial test. I am thinking that we might need
to pre-pin memory pool.

Shirley