netdev - Re: [RFC PATCH 0/1] macvtap TX zero copy between guest and host kernel

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Message-ID: <20100914120545.GC703@redhat.com>
Date:	Tue, 14 Sep 2010 14:05:45 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Shirley Ma <mashirle@...ibm.com>
Cc:	Avi Kivity <avi@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	xiaohui.xin@...el.com, netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/1] macvtap TX zero copy between guest and host
 kernel

On Mon, Sep 13, 2010 at 01:43:00PM -0700, Shirley Ma wrote:
> This patch induces a new sock flag ZEROCOPY to avoid copy between
> userspace and kernel. macvtap is the first user of zero copy between
> guest and host kernel. It only uses when the lower device supports high
> memory DMA. The first set of patch only addresses transmission TX side.
> The test has shown big improvement on either CPU utilization reduction
> or BW increase on 10GbE Intel NIC. Performance data will be submitted in
> the coming email.
> 
> thanks
> Shirley

While others pointed out correctness issues with the patch,
I would still like to see the performance numbers, just so we
understand what's possible.

-- 
MST
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