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To: Gopakumar Choorakkot Edakkunni <gopakumar.c.e@gmail.com>, dev@dpdk.org,
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From: Ferruh Yigit <ferruh.yigit@intel.com>
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Date: Thu, 4 Aug 2016 17:14:26 +0100
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Subject: Re: [dpdk-dev] dpdk 16.07,
 issues with rte_mempool_create and rte_kni_alloc()
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On 8/1/2016 10:19 PM, Gopakumar Choorakkot Edakkunni wrote:
> Well, for my purpose I just ended up creating a seperate/smaller pool
> earlier during bootup to try to guarantee its from one memseg.
> 
> But I am assuming that this KNI restriction is something thats "currently"
> not fixed and is "fixable" ? 


> Any ideas on what the summary of the reason
> for this restriction is - I was gonna check if I can fix that

KNI expects all mbufs are from a physically continuous memory. This is
because of current address translation implementation.

mbufs allocated in userspace and accessed from both user and kernel
space, so mbuf userspace virtual address needs to be converted into
kernelspace virtual address.

Currently this address translation done by first calculating an offset
between virtual addresses using first filed of mempool, later applying
same offset to all mbufs. This is why all mbufs should be in physically
continuous memory.

I think this address translation can be done in different way which can
remove the restriction, but not sure about the effect of the
performance. I will send a patch for this.

Regards,
ferruh