[dpdk-dev] [PATCH v4 3/3] efd: run-time dispatch over x86 EFD functions

Li, Xiaoyun xiaoyun.li at intel.com
Tue Oct 3 10:15:15 CEST 2017


Hi

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Tuesday, October 3, 2017 00:52
> To: Li, Xiaoyun <xiaoyun.li at intel.com>; Richardson, Bruce
> <bruce.richardson at intel.com>
> Cc: Lu, Wenzhuo <wenzhuo.lu at intel.com>; Zhang, Helin
> <helin.zhang at intel.com>; dev at dpdk.org
> Subject: RE: [PATCH v4 3/3] efd: run-time dispatch over x86 EFD functions
> 
> 
> 
> > -----Original Message-----
> > From: Li, Xiaoyun
> > Sent: Monday, October 2, 2017 5:13 PM
> > To: Ananyev, Konstantin <konstantin.ananyev at intel.com>; Richardson,
> > Bruce <bruce.richardson at intel.com>
> > Cc: Lu, Wenzhuo <wenzhuo.lu at intel.com>; Zhang, Helin
> > <helin.zhang at intel.com>; dev at dpdk.org; Li, Xiaoyun
> > <xiaoyun.li at intel.com>
> > Subject: [PATCH v4 3/3] efd: run-time dispatch over x86 EFD functions
> >
> > This patch dynamically selects x86 EFD functions at run-time.
> > This patch uses function pointer and binds it to the relative function
> > based on CPU flags at constructor time.
> >
> > Signed-off-by: Xiaoyun Li <xiaoyun.li at intel.com>
> > ---
> >  lib/librte_efd/rte_efd_x86.h | 41
> > ++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 38 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/librte_efd/rte_efd_x86.h
> > b/lib/librte_efd/rte_efd_x86.h index 34f37d7..93b6743 100644
> > --- a/lib/librte_efd/rte_efd_x86.h
> > +++ b/lib/librte_efd/rte_efd_x86.h
> > @@ -43,12 +43,29 @@
> >  #define EFD_LOAD_SI128(val) _mm_lddqu_si128(val)  #endif
> >
> > +typedef efd_value_t
> > +(*efd_lookup_internal_avx2_t)(const efd_hashfunc_t *group_hash_idx,
> > +		const efd_lookuptbl_t *group_lookup_table,
> > +		const uint32_t hash_val_a, const uint32_t hash_val_b);
> > +
> > +static efd_lookup_internal_avx2_t efd_lookup_internal_avx2_ptr;
> > +
> >  static inline efd_value_t
> >  efd_lookup_internal_avx2(const efd_hashfunc_t *group_hash_idx,
> >  		const efd_lookuptbl_t *group_lookup_table,
> >  		const uint32_t hash_val_a, const uint32_t hash_val_b)  { -
> #ifdef
> > RTE_MACHINE_CPUFLAG_AVX2
> > +	return (*efd_lookup_internal_avx2_ptr)(group_hash_idx,
> > +					       group_lookup_table,
> > +					       hash_val_a, hash_val_b);
> 
> I don't think you need all that.
> All you need - build proper avx2 function even if current HW doesn't support
> it.
> The existing runtime selection here seems ok already.
> Konstantin
> 

Sorry, not quite understand here. So don't need to change codes of efd here?
I didn't care about the HW. CC_SUPPORT_AVX2 only means the compiler supports AVX2 since would runtime selection.
The existing codes RTE_MACHINE_CPUFLAG_AVX2 means both the compiler and HW supports AVX2.


Best Regards,
Xiaoyun Li


> > +}
> > +
> > +#ifdef CC_SUPPORT_AVX2
> > +static inline efd_value_t
> > +efd_lookup_internal_avx2_AVX2(const efd_hashfunc_t *group_hash_idx,
> > +		const efd_lookuptbl_t *group_lookup_table,
> > +		const uint32_t hash_val_a, const uint32_t hash_val_b) {
> >  	efd_value_t value = 0;
> >  	uint32_t i = 0;
> >  	__m256i vhash_val_a = _mm256_set1_epi32(hash_val_a); @@ -
> 74,13
> > +91,31 @@ efd_lookup_internal_avx2(const efd_hashfunc_t
> *group_hash_idx,
> >  	}
> >
> >  	return value;
> > -#else
> > +}
> > +#endif
> > +
> > +static inline efd_value_t
> > +efd_lookup_internal_avx2_DEFAULT(const efd_hashfunc_t
> *group_hash_idx,
> > +		const efd_lookuptbl_t *group_lookup_table,
> > +		const uint32_t hash_val_a, const uint32_t hash_val_b) {
> >  	RTE_SET_USED(group_hash_idx);
> >  	RTE_SET_USED(group_lookup_table);
> >  	RTE_SET_USED(hash_val_a);
> >  	RTE_SET_USED(hash_val_b);
> >  	/* Return dummy value, only to avoid compilation breakage */
> >  	return 0;
> > -#endif
> > +}
> >
> > +static void __attribute__((constructor))
> > +rte_efd_x86_init(void)
> > +{
> > +#ifdef CC_SUPPORT_AVX2
> > +	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX2))
> > +		efd_lookup_internal_avx2_ptr =
> efd_lookup_internal_avx2_AVX2;
> > +	else
> > +		efd_lookup_internal_avx2_ptr =
> efd_lookup_internal_avx2_DEFAULT;
> > +#else
> > +	efd_lookup_internal_avx2_ptr = efd_lookup_internal_avx2_DEFAULT;
> > +#endif
> >  }
> > --
> > 2.7.4



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