netdev - Re: [PATCH 0/9 Rev3] Implement batching skb API and support in IPoIB

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Date:	Fri, 24 Aug 2007 11:46:26 -0700
From:	Rick Jones <rick.jones2@...com>
To:	Bill Fink <billfink@...dspring.com>
Cc:	hadi@...erus.ca, David Miller <davem@...emloft.net>,
	krkumar2@...ibm.com, gaagaan@...il.com,
	general@...ts.openfabrics.org, herbert@...dor.apana.org.au,
	jagana@...ibm.com, jeff@...zik.org, johnpol@....mipt.ru,
	kaber@...sh.net, mcarlson@...adcom.com, mchan@...adcom.com,
	netdev@...r.kernel.org, peter.p.waskiewicz.jr@...el.com,
	rdreier@...co.com, Robert.Olsson@...a.slu.se,
	shemminger@...ux-foundation.org, sri@...ibm.com, tgraf@...g.ch,
	xma@...ibm.com
Subject: Re: [PATCH 0/9 Rev3] Implement batching skb API and support in IPoIB

Bill Fink wrote:
> On Thu, 23 Aug 2007, Rick Jones wrote:
> 
> 
>>jamal wrote:
>>
>>>[TSO already passed - iirc, it has been
>>>demostranted to really not add much to throughput (cant improve much
>>>over closeness to wire speed) but improve CPU utilization].
>>
>>In the one gig space sure, but in the 10 Gig space, TSO on/off does make a 
>>difference for throughput.
> 
> 
> Not too much.
> 
> TSO enabled:
> 
> [root@...g2 ~]# ethtool -k eth2
> Offload parameters for eth2:
> rx-checksumming: on
> tx-checksumming: on
> scatter-gather: on
> tcp segmentation offload: on
> 
> [root@...g2 ~]# nuttcp -w10m 192.168.88.16
> 11813.4375 MB /  10.00 sec = 9906.1644 Mbps 99 %TX 80 %RX
> 
> TSO disabled:
> 
> [root@...g2 ~]# ethtool -K eth2 tso off
> [root@...g2 ~]# ethtool -k eth2
> Offload parameters for eth2:
> rx-checksumming: on
> tx-checksumming: on
> scatter-gather: on
> tcp segmentation offload: off
> 
> [root@...g2 ~]# nuttcp -w10m 192.168.88.16
> 11818.2500 MB /  10.00 sec = 9910.0176 Mbps 100 %TX 78 %RX
> 
> Pretty negligible difference it seems.

Leaves one wondering how often more than one segment was sent to the card in the 
9000 byte case :)

rick jones
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