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

[Jerin Jacob Kollanukkaran]

> -----Original Message-----
> From: Burakov, Anatoly <anatoly.burakov at intel.com>
> Sent: Tuesday, June 25, 2019 7:09 PM
> To: Jerin Jacob Kollanukkaran <jerinj at marvell.com>; 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 12:30 PM, Burakov, Anatoly wrote:
> > 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.
> 
> On another thought, such a default would break 4K pages in case for packets
> bigger than page size (i.e. jumbo frames). Should we care?

The hugepage size will not be 4K. Right?

Olivier,

As a maintainer any thoughts of exposing/not exposing the new mepool flag to
Skip the page boundaries?

All,
Either option is fine, Asking for feedback to processed further?