Re: [dpdk-dev] [PATCH 3/4] eal/arm: Enable lpm/table/pipeline libs

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Wed, Dec 02, 2015 at 05:57:10PM +0100, Thomas Monjalon wrote:
> 2015-12-02 22:23, Jerin Jacob:
> > On Wed, Dec 02, 2015 at 05:40:13PM +0100, Thomas Monjalon wrote:
> > > 2015-12-02 20:04, Jerin Jacob:
> > > > On Wed, Dec 02, 2015 at 09:13:51PM +0800, Jianbo Liu wrote:
> > > > > On 2 December 2015 at 18:39, Jerin Jacob <jerin.jacob@caviumnetworks.com> wrote:
> > > > > > AND they include "rte_lpm.h"(it internally includes rte_vect.h)
> > > > > > that lead to multiple definition and its not good.
> > > > > >
> > > > > But you will have similar issue since "typedef int32x4_t __m128i"
> > > > > appears in both your patch and this header file.
> > > >
> > > > I just tested it, it won't break, back to back "typedef int32x4_t __m128i"
> > > > is fine(unlike inline function).
> > > >
> > > > my intention to keep __m128i "as is"  because changing the __m128i to rte_???
> > > > something would break the ABI.
> > >
> > > Isn't it already broken in 2.2?
> >
> > Does it mean, You would like to have rte_128i(or similar) kind of
> > abstraction to represent 128bit SIMD variable in DPDK?
>
> If you are convinced that it is the best way to write a generic code, yes.

I grep-ed through DPDK API list to see the dependency with SIMD in API
definition.I see only rte_lpm_lookupx4 API has SIMD dependency in API
definition.

I believe that's the root cause of the problem. IMO, The
better way to fix this would be to remove __m128i from API and have more
general representation to remove the architecture dependency from API

something like this,

rte_lpm_lookupx4(const struct rte_lpm *lpm, uint32_t *ip, uint16_t
hop[4], uint16_t defv)

instead of

rte_lpm_lookupx4(const struct rte_lpm *lpm, __m128i ip, uint16_t
hop[4],  uint16_t defv)

Now I am not sure why this API was created like this, from l3fwd.c
example, it looks to accommodate the IPV4 byte swap[1]. If it's true,
maybe we can have eal byte swap abstraction for optimized byte swap on
memory for 4 IP address in one shot

or

Have rte_lpm_lookupx4 take an argument for byte swap or not ?

or

something similar?

Thoughts ?

[1]
const  __m128i bswap_mask = _mm_set_epi8(12, 13, 14, 15, 8, 9, 10, 11,
                                                4, 5, 6, 7, 0, 1, 2, 3);
/* Byte swap 4 IPV4 addresses. */
dip = _mm_shuffle_epi8(dip, bswap_mask);

Jerin

> I think the most important question is to know what is the best solution
> for performance and maintainability. The API/ABI questions will be considered
> after.
>
> Thanks for your involvement guys.