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Date:	Mon, 24 Sep 2007 11:22:50 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Rick Jones <rick.jones2@...com>
CC:	Steve Wise <swise@...ngridcomputing.com>, hadi@...erus.ca,
	Evgeniy Polyakov <johnpol@....mipt.ru>, netdev@...r.kernel.org,
	Robert Olsson <Robert.Olsson@...a.slu.se>
Subject: Re: pktgen question

Rick Jones wrote:
>>> Perf-wise, you could clone the skbs up front, then deliver them to 
>>> the nic in a tight loop.  This would mitigate the added overhead 
>>> introduced by calling skb_clone() in the loop doing transmits...
>>
>> That only works if you are sending a small number of skbs.  You can't 
>> pre-clone several minutes worth of 10Gbe traffic
>> with any normal amount of RAM.
> 
> Does pktgen really need to allocate anything more than some smallish 
> fraction more than the depth of the driver's transmit queue?

If you want to send sustained high rates of traffic, for more than
just a trivial amount of time, then you either have to play the current
trick with the skb_get(), or you have to allocate a real packet each time
(maybe with skb_clone() or similar, but it's still more overhead than the skb_get
which only bumps a reference count.)

I see no other way, but if you can think of one, please let me know.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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