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

[Olivier Matz <olivier.matz@6wind.com>]

Hi,

On Mon, Jul 15, 2019 at 10:38:53AM +0100, Burakov, Anatoly wrote:
> On 15-Jul-19 5:54 AM, Jerin Jacob Kollanukkaran wrote:
> > > > > > > > (also, i don't really like the name NO_PAGE_BOUND since in
> > > > > > > > memzone API there's a "bounded memzone" allocation API, and this
> > > > > > > > flag's name reads like objects would not be bounded by page size,
> > > > > > > > not that they won't cross page
> > > > > > > > boundary)
> > > > > > > 
> > > > > > > No strong opinion for the name. What name you suggest?
> > > > > > 
> > > > > > How about something like MEMPOOL_F_NO_PAGE_SPLIT?
> > > > > 
> > > > > Looks good to me.
> > > > > 
> > > > > In summary, Change wrt existing patch"
> > > > > - Change NO_PAGE_BOUND to MEMPOOL_F_NO_PAGE_SPLIT
> > > > > - Set this flag in  rte_pktmbuf_pool_create () when
> > > > rte_eal_has_hugepages() ||
> > > > >    rte_malloc_heap_socket_is_external(socket_id))
> > > > 
> > > > If we are to have a special KNI allocation API, would we even need that?
> > > 
> > > Not need this change in rte_pktmbuf_pool_create () if we introduce a new
> > > rte_kni_pktmbuf_pool_create () API.
> > 
> > Ferruh, Olivier, Anatoly,
> > 
> > Any objection to create new rte_kni_pktmbuf_pool_create () API
> > to embedded MEMPOOL_F_NO_PAGE_SPLIT flag requirement for KNI + IOVA as VA
> > 
> > 
> 
> As long as we all are aware of what that means and agree with that
> consequence (namely, separate codepaths for KNI and other PMD's) then i have
> no specific objections.

Sorry for the late feedback.

I think we can change the default behavior of mempool populate(), to
prevent objects from being accross 2 pages, except if the size of the
object is bigger than the size of the page. This is already what is done
in rte_mempool_op_calc_mem_size_default() when we want to estimate the
amount of memory needed to allocate N objects.

This would avoid the introduction of a specific API to allocate packets
for kni, and a specific mempool flag.

About the problem of 9K mbuf mentionned by Anatoly, could we imagine a
check in kni code, that just returns an error "does not work with
size(mbuf) > size(page)" ?

Thanks,
Olivier