Re: [dpdk-dev] Aligned RX data.

[Alex Markuze <alex@weka.io>]

Very helpful, thanks a lot.
It sure does seem to do the trick.

On Mon, Oct 13, 2014 at 2:43 PM, Ananyev, Konstantin <
konstantin.ananyev@intel.com> wrote:

>
>
> > -----Original Message-----
> > From: Ananyev, Konstantin
> > Sent: Monday, October 13, 2014 12:30 PM
> > To: Ananyev, Konstantin
> > Subject: FW: [dpdk-dev] Aligned RX data.
> >
> >
> >
> > From: Alex Markuze [mailto:alex@weka.io]
> > Sent: Monday, October 13, 2014 9:47 AM
> > To: Ananyev, Konstantin
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] Aligned RX data.
> >
> > Hi All,
> > Is there a way to create a mempool such that all mbufs are aligned to X.
> lets say X is 512.
> >
> > Thanks.
> >
>
> For example something like that:
>
> struct rte_mempool *
> mempool_xz1_create(uint32_t elt_num, int32_t socket_id)
> {
>         struct rte_mempool *mp;
>         const struct rte_memzone *mz;
>         struct rte_mempool_objsz obj_sz;
>         uint32_t flags, elt_size, total_size;
>         size_t sz;
>         phys_addr_t pa;
>         void *va;
>
>         /* mp element header_size==64B,  trailer_size==0. */
>         flags = MEMPOOL_F_NO_SPREAD;
>
>         /* to make total element size of mp 2K. */
>         elt_size = 2048 - 64;
>
>         total_size = rte_mempool_calc_obj_size(elt_size, flags, &obj_sz);
>         sz = elt_num * total_size + 512;
>
>         if ((mz = rte_memzone_reserve_aligned("xz1_obj", sz, socket_id,
>                         0, 512)) == NULL)
>                 return (NULL);
>
>         va = (char *)mz->addr + 512 - obj_sz.header_size;
>         pa = mz->phys_addr + 512 - obj_sz.header_size;
>
>         mp = rte_mempool_xmem_create("xz1", elt_num, elt_size,
>                 256, sizeof(struct rte_pktmbuf_pool_private),
>                 rte_pktmbuf_pool_init, NULL,
>                 rte_pktmbuf_init, NULL,
>                 socket_id, flags, va, &pa,
>                 MEMPOOL_PG_NUM_DEFAULT, MEMPOOL_PG_SHIFT_MAX);
>
>         return (mp);
> }
>
> Each mbuf will be aligned on 512B boundary and  1856 (2K - 64B header -
> 128B mbuf).
>
> Alternative way - is to provide your own element constructor instead of
> rte_pktmbuf_init() for mempool_create.
> And inside it align buf_addr and buf_physaddr.
> Though in that case you have to set RTE_MBUF_REFCNT=n in your config.
> That's why I'd say it is a not recommended.
>
> Konstantin
>
> >
> > On Sat, Oct 11, 2014 at 5:04 PM, Alex Markuze <alex@weka.io> wrote:
> > O.k, And how would I do that?
> > I'm guessing there is something I can control in rte_pktmbuf_pool_init?
> > I would appreciate If you could spare a word or two in the matter.
> >
> > On Tue, Oct 7, 2014 at 7:11 PM, Ananyev, Konstantin <
> konstantin.ananyev@intel.com> wrote:
> >
> >
> > > -----Original Message-----
> > > From: Ananyev, Konstantin
> > > Sent: Tuesday, October 07, 2014 5:03 PM
> > > To: Ananyev, Konstantin
> > > Subject: FW: [dpdk-dev] Aligned RX data.
> > >
> > >
> > >
> > > From: Alex Markuze [mailto:alex@weka.io]
> > > Sent: Tuesday, October 07, 2014 4:52 PM
> > > To: Ananyev, Konstantin
> > > Cc: dev@dpdk.org
> > > Subject: Re: [dpdk-dev] Aligned RX data.
> > >
> > > RTE_PKTMBUF_HEADROOM defines the headroom
> >
> > Yes.
> >
> > >this would be true only if the buff_start was aligned to 512 which is
> not.
> >
> > As I said: " Make sure that your all your mbufs are aligned by 512".
> >
> > Konstantin
> >
> > >
> > > On Tue, Oct 7, 2014 at 1:05 PM, Ananyev, Konstantin <
> konstantin.ananyev@intel.com> wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Alex Markuze
> > > > Sent: Tuesday, October 07, 2014 10:40 AM
> > > > To: dev@dpdk.org
> > > > Subject: [dpdk-dev] Aligned RX data.
> > > >
> > > > Hi , I'm trying to receive aligned packets from the wire.
> > > > Meaning that for all received packets the pkt.data is always aligned
> to
> > > > (512 -H).
> > > >
> > > > Looking at the pmds of ixgbe/vmxnet I see that the pmds call
> > > > __rte_mbuf_raw_alloc and set the rx descriptor with a
> > > > RTE_MBUF_DATA_DMA_ADDR_DEFAULT
> > > > Instead of the more appropriate RTE_MBUF_DATA_DMA_ADDR.
> > > >
> > > > Do I need to modify each pmd I'm using to be able to receive aligned
> data?
> > > Make sure that your all your mbufs are aligned by 512 and set in your
> config RTE_PKTMBUF_HEADROOM=512-H?
> > >
> > >
> > > > Or have I missed something?
> > > >
> > > > Thanks
> >
>
>