linux-kernel - Re: Got iperf regression while intel_iommu is on, how to cut the cost of cache flushing

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Message-ID: <1384220059.13547.17.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 11 Nov 2013 17:34:19 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ethan Zhao <ethan.kernel@...il.com>
Cc:	Ashok Raj <ashok.raj@...el.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Got iperf regression while intel_iommu is on, how to cut the
 cost of cache flushing

On Tue, 2013-11-12 at 09:03 +0800, Ethan Zhao wrote:
> Eric,
>     We have tested the performance with the TSO and TSQ patches
> merged, the result not good, even worse than kernel without those two
> patches. any idea ?
> 
> kernel   : 3.11.x with TSO & TSQ merged.  ( CONFIG_INTEL_IOMMU_DEFAULT_ON=y )
> Network Interface : eth4
> Network driver    : be2net
> 
> Average Bandwidth for :
>    1.tcp-unidirectional test    : 4385 Mbits/sec
>    2.tcp-unidirectional-parallel: 9383 Mbits/sec
>    3.tcp-bidirectonal test      : 2755 Mbits/sec
> 
> vs
> 
> kernel   :  3.11.x without TSO & TSQ patches.
> (CONFIG_INTEL_IOMMU_DEFAULT_ON is not set)
> Network Interface : eth4
> Network driver    : be2net
> 
> Average Bandwidth for :
>    1.tcp-unidirectional test    : 7992 Mbits/sec
>    2.tcp-unidirectional-parallel: 9403 Mbits/sec
>    3.tcp-bidirectonal test      : 5802 Mbits/sec
> 

So it seems its not the TSO/TSQ changes, but
CONFIG_INTEL_IOMMU_DEFAULT_ON being on instead of off.



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