netdev - Re: [PATCH V3 0/8] macvtap/vhost TX zero copy support

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Date:	Fri, 22 Apr 2011 10:52:53 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	David Miller <davem@...emloft.net>
Cc:	mst@...hat.com, Eric Dumazet <eric.dumazet@...il.com>,
	Avi Kivity <avi@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 0/8] macvtap/vhost TX zero copy support

On Wed, 2011-04-20 at 12:36 -0700, Shirley Ma wrote:
> I am collecting more test results against 2.6.39-rc3 kernel and will
> provide the test matrix later.

Single TCP_STREAM 120 secs test results over ixgbe 10Gb NIC results:

Message	BW(Gb/s)qemu-kvm (NumCPU)vhost-net(NumCPU) PerfTop irq/s
4K	7408.57		92.1%		22.6%		1229
4K(Orig)4913.17		118.1%		84.1%		2086	
8K	9129.90		89.3%		23.3%		1141
8K(Orig)7094.55		115.9%		84.7%		2157
16K	9178.81		89.1%		23.3%		1139
16K(Orig)8927.1		118.7%		83.4%		2262
64K	9171.43		88.4%		24.9%		1253
64K(Orig)9085.85        115.9%		82.4%		2229

For message size less or equal than 2K, there is a known KVM guest TX
overrun issue. With this zerocopy patch, the issue becomes more severe,
guest io_exits has tripled than before, so the performance is not good.
Once the TX overrun problem has been addressed, I will retest the small
message size performance.

Thanks
Shirley

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