Re: [PATCH v3 0/2] slow data path communication between DPDK port and Linux

From: Panu Matilainen <pmatilai@redhat.com>
To: Ferruh Yigit <ferruh.yigit@intel.com>,
	Thomas Monjalon <thomas.monjalon@6wind.com>
Cc: dev@dpdk.org, David Marchand <david.marchand@6wind.com>,
	Helin Zhang <helin.zhang@intel.com>
Subject: Re: [PATCH v3 0/2] slow data path communication between DPDK port and Linux
Date: Wed, 16 Mar 2016 15:23:14 +0200	[thread overview]
Message-ID: <56E95E42.9000206@redhat.com> (raw)
In-Reply-To: <56E93FF2.8010501@intel.com>

On 03/16/2016 01:13 PM, Ferruh Yigit wrote:
> On 3/16/2016 10:45 AM, Thomas Monjalon wrote:
>> 2016-03-16 10:26, Ferruh Yigit:
>>> On 3/16/2016 8:22 AM, Panu Matilainen wrote:
>>>> On 03/16/2016 10:19 AM, Ferruh Yigit wrote:
>>>>> On 3/16/2016 7:26 AM, Panu Matilainen wrote:
>>>>>> On 03/14/2016 05:32 PM, Ferruh Yigit wrote:
>>>>>>> On 3/9/2016 11:17 AM, Ferruh Yigit wrote:
>>>>>>>> This patch sent to keep record of latest status of the work.
>>>>>>>>
>>>>>>>>
>>>>>>>> This is slow data path communication implementation based on existing KNI.
>>>>>>>>
>>>>>>>> Difference is: librte_kni converted into a PMD, kdp kernel module is almost
>>>>>>>> same except all control path functionality removed and some simplification done.
>>>>>>>>
>>>>>>>> Motivation is to simplify slow path data communication.
>>>>>>>> Now any application can use this new PMD to send/get data to Linux kernel.
>>>>>>>>
>>>>>>>> PMD supports two communication methods:
>>>>>>>>
>>>>>>>> 1) KDP kernel module
>>>>>>>> PMD initialization functions handles creating virtual interfaces (with help of
>>>>>>>> kdp kernel module) and created FIFO. FIFO is used to share data between
>>>>>>>> userspace and kernelspace. This is default method.
>>>>>>>>
>>>>>>>> 2) tun/tap module
>>>>>>>> When KDP module is not inserted, PMD creates tap interface and transfers
>>>>>>>> packets using tap interface.
>>>>>>>>
>>>>>>>> In long term this patch intends to replace the KNI and KNI will be
>>>>>>>> depreciated.
>>>>>>>>
>>>>>>>
>>>>>>> Self-NACK: Will work on another option that does not introduce new
>>>>>>> kernel module.
>>>>>>>
>>>>>>
>>>>>> Hmm, care to elaborate a bit? The second mode of this PMD already was
>>>>>> free of external kernel modules. Do you mean you'll be just removing
>>>>>> mode 1) from the PMD or looking at something completely different?
>>>>>>
>>>>>> Just thinking that tun/tap PMD sounds like a useful thing to have, I
>>>>>> hope you're not abandoning that.
>>>>>>
>>>>>
>>>>> It will be KNI PMD.
>>>>> Plan is to have something like KDP, but with existing KNI kernel module.
>>>>> There will be tun/tap support as fallback.
>>>>
>>>> Hum, now I'm confused. I was under the impression everybody hated KNI
>>>> and wanted to get rid of it, and certainly not build future solutions on
>>>> top of it?
>>>
>>> We can't remove it.
>>
>> Why?
>>
>>> We can't replace/improve it -you were one of the major opposition to this.
>>> This doesn't leave more option other than using it.
>>
>> Why cannot we replace it by something upstream?
>>
> I doubt KDP is upstream-able to Linux community. If somebody can, that
> is great.
>
> Even for KCP, upstreaming task is still under discussion, and as a heads
> up, it is likely to be dropped.

If KCP/KDP are not upstreamable then the solution is to find another way 
that is.

Easier said than done, no doubt.

	- Panu -