Re: [dpdk-dev] [PATCH] app/testpmd: improve MAC swap performance

[Wiles, Keith]

> On Nov 20, 2018, at 3:16 AM, Ananyev, Konstantin 
> <konstantin.anan...@intel.com> wrote:
> 
> Hi Qi,
> 
>> -----Original Message-----
>> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Qi Zhang
>> Sent: Tuesday, November 20, 2018 4:46 AM
>> To: Richardson, Bruce <bruce.richard...@intel.com>; Wiles, Keith 
>> <keith.wi...@intel.com>
>> Cc: dev@dpdk.org; Lu, Wenzhuo <wenzhuo...@intel.com>; Iremonger, Bernard 
>> <bernard.iremon...@intel.com>; Zhang, Qi Z
>> <qi.z.zh...@intel.com>; sta...@dpdk.org
>> Subject: [dpdk-dev] [PATCH] app/testpmd: improve MAC swap performance
>> 
>> The patch optimizes the mac swap operation by taking advantage
>> of SSE instructions, it only impacts x86 platform.
>> 
>> Cc: sta...@dpdk.org
>> 
>> Signed-off-by: Qi Zhang <qi.z.zh...@intel.com>
>> ---
>> app/test-pmd/macswap.c | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>> 
>> diff --git a/app/test-pmd/macswap.c b/app/test-pmd/macswap.c
>> index a8384d5b8..0722782b0 100644
>> --- a/app/test-pmd/macswap.c
>> +++ b/app/test-pmd/macswap.c
>> @@ -78,7 +78,6 @@ pkt_burst_mac_swap(struct fwd_stream *fs)
>>      struct rte_port  *txp;
>>      struct rte_mbuf  *mb;
>>      struct ether_hdr *eth_hdr;
>> -    struct ether_addr addr;
>>      uint16_t nb_rx;
>>      uint16_t nb_tx;
>>      uint16_t i;
>> @@ -95,6 +94,15 @@ pkt_burst_mac_swap(struct fwd_stream *fs)
>>      start_tsc = rte_rdtsc();
>> #endif
>> 
>> +#ifdef RTE_ARCH_X86
>> +    __m128i addr;
>> +    __m128i shfl_msk = _mm_set_epi8(15, 14, 13, 12,
>> +                                    5, 4, 3, 2,
>> +                                    1, 0, 11, 10,
>> +                                    9, 8, 7, 6);
>> +#else
>> +    struct ether_addr addr;
>> +#endif
> 
> I think it would better to place IA specific code into a separate fnction
> (and probably into a separate .h file).
> BTW, just curious what % of improvement it gives?
> Konstantin
> 

If we are going to the trouble of moving the code out of the .c into a .h then 
I suggest it be placed into the rte_ethdev headers for everyone to use.
> 
>>      /*
>>       * Receive a burst of packets and forward them.
>>       */
>> @@ -123,9 +131,15 @@ pkt_burst_mac_swap(struct fwd_stream *fs)
>>              eth_hdr = rte_pktmbuf_mtod(mb, struct ether_hdr *);
>> 
>>              /* Swap dest and src mac addresses. */
>> +#ifdef RTE_ARCH_X86
>> +            addr = _mm_loadu_si128((__m128i *)eth_hdr);
>> +            addr = _mm_shuffle_epi8(addr, shfl_msk);
>> +            _mm_storeu_si128((__m128i *)eth_hdr, addr);
>> +#else
>>              ether_addr_copy(&eth_hdr->d_addr, &addr);
>>              ether_addr_copy(&eth_hdr->s_addr, &eth_hdr->d_addr);
>>              ether_addr_copy(&addr, &eth_hdr->s_addr);
>> +#endif
>> 
>>              mb->ol_flags &= IND_ATTACHED_MBUF | EXT_ATTACHED_MBUF;
>>              mb->ol_flags |= ol_flags;
>> --
>> 2.13.6

Regards,
Keith