Subject: Re: [RFC] [PATCH 0/3] ioat: DMA engine support

From: Avi Kivity <[email-masked]>
Date: Thu, 24 Nov 2005 17:35:26 +0200

Andi Kleen wrote:

>>>      
>>>
>>As an example, an NFS server reads some data pages using iSCSI and sends 
>>them using NFS/TCP (or vice versa).
>>    
>>
>
>For TX this can be done zero copy using a sendfile like setup.
>  
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Yes, or with aio send for anonymous memory.

>For RX it may help - but my point was that most applications
>are not structured in this simple way.
>
>  
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Agreed. But those that do care, care very much. The data mover 
applications, simply because they don't touch the data, expect very high 
bandwidth.

>>As long as they can be turned off. Not all usespace applications want to 
>>touch the data immediately.
>>    
>>
>
>Perhaps.  And lots of others might. Of course the simple
>network benchmarks don't so the number on them look good.
>
>  
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There are very real non-benchmark applications that want this.

>Just pointing out that it's not clear it will always be a big help.
>
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Agree it should default to in-cache.