[dpdk-dev] [PATCH v6 0/4] add IOVA = VA support in KNI

Burakov, Anatoly anatoly.burakov at intel.com
Tue Jun 25 13:30:26 CEST 2019


On 25-Jun-19 12:15 PM, Jerin Jacob Kollanukkaran wrote:
>> -----Original Message-----
>> From: dev <dev-bounces at dpdk.org> On Behalf Of Burakov, Anatoly
>> Sent: Tuesday, June 25, 2019 3:30 PM
>> To: Vamsi Krishna Attunuru <vattunuru at marvell.com>; dev at dpdk.org
>> Cc: ferruh.yigit at intel.com; olivier.matz at 6wind.com;
>> arybchenko at solarflare.com
>> Subject: Re: [dpdk-dev] [PATCH v6 0/4] add IOVA = VA support in KNI
>>
>> On 25-Jun-19 4:56 AM, vattunuru at marvell.com wrote:
>>> From: Vamsi Attunuru <vattunuru at marvell.com>
>>>
>>> ----
>>> V6 Changes:
>>> * Added new mempool flag to ensure mbuf memory is not scattered across
>>> page boundaries.
>>> * Added KNI kernel module required PCI device information.
>>> * Modified KNI example application to create mempool with new mempool
>>> flag.
>>>
>> Others can chime in, but my 2 cents: this reduces the usefulness of KNI because
>> it limits the kinds of mempools one can use them with, and makes it so that the
>> code that works with every other PMD requires changes to work with KNI.
> 
> # One option to make this flag as default only for packet mempool(not allow allocate on page boundary).
> In real world the overhead will be very minimal considering Huge page size is 1G or 512M
> # Enable this flag explicitly only IOVA = VA mode in library. Not  need to expose to application
> # I don’t think, there needs to be any PMD specific change to make KNI with IOVA = VA mode
> # No preference on flags to be passed by application vs in library. But IMO this change would be
> needed in mempool support KNI in IOVA = VA mode.
> 

I would be OK to just make it default behavior to not cross page 
boundaries when allocating buffers. This would solve the problem for KNI 
and for any other use case that would rely on PA-contiguous buffers in 
face of IOVA as VA mode.

We could also add a flag to explicitly allow page crossing without also 
making mbufs IOVA-non-contiguous, but i'm not sure if there are use 
cases that would benefit from this.

> 
> 
>>
>> --
>> Thanks,
>> Anatoly


-- 
Thanks,
Anatoly


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