[dpdk-dev] [EXT] Re: [PATCH v1 20/26] node: ipv4 lookup for x86

[Pavan Nikhilesh Bhagavatula]

>-----Original Message-----
>From: Ray Kinsella <mdr at ashroe.eu>
>Sent: Thursday, March 19, 2020 9:21 PM
>To: Pavan Nikhilesh Bhagavatula <pbhagavatula at marvell.com>; Jerin
>Jacob Kollanukkaran <jerinj at marvell.com>; Nithin Kumar Dabilpuram
><ndabilpuram at marvell.com>
>Cc: dev at dpdk.org; thomas at monjalon.net;
>david.marchand at redhat.com; mattias.ronnblom at ericsson.com; Kiran
>Kumar Kokkilagadda <kirankumark at marvell.com>
>Subject: Re: [EXT] Re: [dpdk-dev] [PATCH v1 20/26] node: ipv4 lookup
>for x86
>
>
>
>On 19/03/2020 14:22, Pavan Nikhilesh Bhagavatula wrote:
>>> On 18/03/2020 21:35, jerinj at marvell.com wrote:
>>>> From: Pavan Nikhilesh <pbhagavatula at marvell.com>
>>>>
>>>> Add IPv4 lookup process function for ip4_lookup
>>>> rte_node. This node performs LPM lookup using x86_64
>>>> vector supported RTE_LPM API on every packet received
>>>> and forwards it to a next node that is identified by
>>>> lookup result.
>>>>
>>>> Signed-off-by: Pavan Nikhilesh <pbhagavatula at marvell.com>
>>>> Signed-off-by: Nithin Dabilpuram <ndabilpuram at marvell.com>
>>>> Signed-off-by: Kiran Kumar K <kirankumark at marvell.com>
>>>> ---
>>>>  lib/librte_node/ip4_lookup.c | 245
>>> +++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 245 insertions(+)
>>>>
>>>> diff --git a/lib/librte_node/ip4_lookup.c
>>> b/lib/librte_node/ip4_lookup.c
>>>> index d7fcd1158..c003e9c91 100644
>>>> --- a/lib/librte_node/ip4_lookup.c
>>>> +++ b/lib/librte_node/ip4_lookup.c
>>>> @@ -264,6 +264,251 @@ ip4_lookup_node_process(struct
>rte_graph
>>> *graph, struct rte_node *node,
>>>>  	return nb_objs;
>>>>  }
>>>>
>>>> +#elif defined(RTE_ARCH_X86)
>>>> +
>>>> +/* X86 SSE */
>>>> +static uint16_t
>>>> +ip4_lookup_node_process(struct rte_graph *graph, struct
>rte_node
>>> *node,
>>>> +			void **objs, uint16_t nb_objs)
>>>> +{
>>>> +	struct rte_mbuf *mbuf0, *mbuf1, *mbuf2, *mbuf3, **pkts;
>>>> +	rte_edge_t next0, next1, next2, next3, next_index;
>>>> +	struct rte_ipv4_hdr *ipv4_hdr;
>>>> +	struct rte_ether_hdr *eth_hdr;
>>>> +	uint32_t ip0, ip1, ip2, ip3;
>>>> +	void **to_next, **from;
>>>> +	uint16_t last_spec = 0;
>>>> +	uint16_t n_left_from;
>>>> +	struct rte_lpm *lpm;
>>>> +	uint16_t held = 0;
>>>> +	uint32_t drop_nh;
>>>> +	rte_xmm_t dst;
>>>> +	__m128i dip; /* SSE register */
>>>> +	int rc, i;
>>>> +
>>>> +	/* Speculative next */
>>>> +	next_index = RTE_NODE_IP4_LOOKUP_NEXT_REWRITE;
>>>> +	/* Drop node */
>>>> +	drop_nh =
>>> ((uint32_t)RTE_NODE_IP4_LOOKUP_NEXT_PKT_DROP) << 16;
>>>> +
>>>> +	/* Get socket specific LPM from ctx */
>>>> +	lpm = *((struct rte_lpm **)node->ctx);
>>>> +
>>>> +	pkts = (struct rte_mbuf **)objs;
>>>> +	from = objs;
>>>> +	n_left_from = nb_objs;
>>>
>>> I doubt this initial prefetch of the first 4 packets has any benefit.
>>
>> Ack will remove in v2 for x86.
>>
>>>
>>>> +	if (n_left_from >= 4) {
>>>> +		for (i = 0; i < 4; i++) {
>>>> +			rte_prefetch0(rte_pktmbuf_mtod(pkts[i],
>>>> +						       struct rte_ether_hdr
>>> *) +
>>>> +				      1);
>>>> +		}
>>>> +	}
>>>> +
>>>> +	/* Get stream for the speculated next node */
>>>> +	to_next = rte_node_next_stream_get(graph, node,
>>> next_index, nb_objs);
>>>
>>> Suggest you don't reuse the hand-unrolling optimization from FD.io
>>> VPP.
>>> I have never found any performance benefit from them, and they
>>> make the code unnecessarily verbose.
>>>
>>
>> How would be take the benefit of rte_lpm_lookupx4 without
>unrolling the loop?.
>> Also, in future if we are using rte_rib and fib with a CPU supporting
>wider SIMD we might
>> need to unroll them further (AVX256 AND 512 currently
>rte_lpm_lookup uses only 128bit
>> since it is only uses SSE extension).
>
>Let the compiler do it for you, but using a constant vector length.
>for (int i=0; i < 4; ++i) { ... }
>

Ok, I think I misunderstood the previous comment. 
It was only for the prefetches in the loop right?

>>
>>>
>>>> +	while (n_left_from >= 4) {
>>>> +		/* Prefetch next-next mbufs */
>>>> +		if (likely(n_left_from >= 11)) {
>>>> +			rte_prefetch0(pkts[8]);
>>>> +			rte_prefetch0(pkts[9]);
>>>> +			rte_prefetch0(pkts[10]);
>>>> +			rte_prefetch0(pkts[11]);
>>>> +		}
>>>> +
>>>> +		/* Prefetch next mbuf data */
>>>> +		if (likely(n_left_from >= 7)) {
>>>> +			rte_prefetch0(rte_pktmbuf_mtod(pkts[4],
>>>> +						       struct rte_ether_hdr
>>> *) +
>>>> +				      1);
>>>> +			rte_prefetch0(rte_pktmbuf_mtod(pkts[5],
>>>> +						       struct rte_ether_hdr
>>> *) +
>>>> +				      1);
>>>> +			rte_prefetch0(rte_pktmbuf_mtod(pkts[6],
>>>> +						       struct rte_ether_hdr
>>> *) +
>>>> +				      1);
>>>> +			rte_prefetch0(rte_pktmbuf_mtod(pkts[7],
>>>> +						       struct rte_ether_hdr
>>> *) +
>>>> +				      1);
>>>> +		}
>>>> +
>>>> +		mbuf0 = pkts[0];
>>>> +		mbuf1 = pkts[1];
>>>> +		mbuf2 = pkts[2];
>>>> +		mbuf3 = pkts[3];
>>>> +
>>>> +		pkts += 4;
>>>> +		n_left_from -= 4;
>>>> +
>>>> +		/* Extract DIP of mbuf0 */
>>>> +		eth_hdr = rte_pktmbuf_mtod(mbuf0, struct
>>> rte_ether_hdr *);
>>>> +		ipv4_hdr = (struct rte_ipv4_hdr *)(eth_hdr + 1);
>>>> +		ip0 = ipv4_hdr->dst_addr;
>>>> +		/* Extract cksum, ttl as ipv4 hdr is in cache */
>>>> +		rte_node_mbuf_priv1(mbuf0)->cksum = ipv4_hdr-
>>>> hdr_checksum;
>>>> +		rte_node_mbuf_priv1(mbuf0)->ttl = ipv4_hdr-
>>>> time_to_live;
>>>> +
>>>> +		/* Extract DIP of mbuf1 */
>>>> +		eth_hdr = rte_pktmbuf_mtod(mbuf1, struct
>>> rte_ether_hdr *);
>>>> +		ipv4_hdr = (struct rte_ipv4_hdr *)(eth_hdr + 1);
>>>> +		ip1 = ipv4_hdr->dst_addr;
>>>> +		/* Extract cksum, ttl as ipv4 hdr is in cache */
>>>> +		rte_node_mbuf_priv1(mbuf1)->cksum = ipv4_hdr-
>>>> hdr_checksum;
>>>> +		rte_node_mbuf_priv1(mbuf1)->ttl = ipv4_hdr-
>>>> time_to_live;
>>>> +
>>>> +		/* Extract DIP of mbuf2 */
>>>> +		eth_hdr = rte_pktmbuf_mtod(mbuf2, struct
>>> rte_ether_hdr *);
>>>> +		ipv4_hdr = (struct rte_ipv4_hdr *)(eth_hdr + 1);
>>>> +		ip2 = ipv4_hdr->dst_addr;
>>>> +		/* Extract cksum, ttl as ipv4 hdr is in cache */
>>>> +		rte_node_mbuf_priv1(mbuf2)->cksum = ipv4_hdr-
>>>> hdr_checksum;
>>>> +		rte_node_mbuf_priv1(mbuf2)->ttl = ipv4_hdr-
>>>> time_to_live;
>>>> +
>>>> +		/* Extract DIP of mbuf3 */
>>>> +		eth_hdr = rte_pktmbuf_mtod(mbuf3, struct
>>> rte_ether_hdr *);
>>>> +		ipv4_hdr = (struct rte_ipv4_hdr *)(eth_hdr + 1);
>>>> +		ip3 = ipv4_hdr->dst_addr;
>>>> +
>>>> +		/* Prepare for lookup x4 */
>>>> +		dip = _mm_set_epi32(ip3, ip2, ip1, ip0);
>>>> +
>>>> +		/* Byte swap 4 IPV4 addresses. */
>>>> +		const __m128i bswap_mask = _mm_set_epi8(
>>>> +			12, 13, 14, 15, 8, 9, 10, 11, 4, 5, 6, 7, 0, 1, 2, 3);
>>>> +		dip = _mm_shuffle_epi8(dip, bswap_mask);
>>>> +
>>>> +		/* Extract cksum, ttl as ipv4 hdr is in cache */
>>>> +		rte_node_mbuf_priv1(mbuf3)->cksum = ipv4_hdr-
>>>> hdr_checksum;
>>>> +		rte_node_mbuf_priv1(mbuf3)->ttl = ipv4_hdr-
>>>> time_to_live;
>>>> +
>>>> +		/* Perform LPM lookup to get NH and next node */
>>>> +		rte_lpm_lookupx4(lpm, dip, dst.u32, drop_nh);
>>>> +
>>>> +		/* Extract next node id and NH */
>>>> +		rte_node_mbuf_priv1(mbuf0)->nh = dst.u32[0] &
>>> 0xFFFF;
>>>> +		next0 = (dst.u32[0] >> 16);
>>>> +
>>>> +		rte_node_mbuf_priv1(mbuf1)->nh = dst.u32[1] &
>>> 0xFFFF;
>>>> +		next1 = (dst.u32[1] >> 16);
>>>> +
>>>> +		rte_node_mbuf_priv1(mbuf2)->nh = dst.u32[2] &
>>> 0xFFFF;
>>>> +		next2 = (dst.u32[2] >> 16);
>>>> +
>>>> +		rte_node_mbuf_priv1(mbuf3)->nh = dst.u32[3] &
>>> 0xFFFF;
>>>> +		next3 = (dst.u32[3] >> 16);
>>>> +
>>>> +		/* Enqueue four to next node */
>>>> +		rte_edge_t fix_spec =
>>>> +			(next_index ^ next0) | (next_index ^ next1) |
>>>> +			(next_index ^ next2) | (next_index ^ next3);
>>>> +
>>>> +		if (unlikely(fix_spec)) {
>>>> +			/* Copy things successfully speculated till now
>>> */
>>>> +			rte_memcpy(to_next, from, last_spec *
>>> sizeof(from[0]));
>>>> +			from += last_spec;
>>>> +			to_next += last_spec;
>>>> +			held += last_spec;
>>>> +			last_spec = 0;
>>>> +
>>>> +			/* Next0 */
>>>> +			if (next_index == next0) {
>>>> +				to_next[0] = from[0];
>>>> +				to_next++;
>>>> +				held++;
>>>> +			} else {
>>>> +				rte_node_enqueue_x1(graph, node,
>>> next0,
>>>> +						    from[0]);
>>>> +			}
>>>> +
>>>> +			/* Next1 */
>>>> +			if (next_index == next1) {
>>>> +				to_next[0] = from[1];
>>>> +				to_next++;
>>>> +				held++;
>>>> +			} else {
>>>> +				rte_node_enqueue_x1(graph, node,
>>> next1,
>>>> +						    from[1]);
>>>> +			}
>>>> +
>>>> +			/* Next2 */
>>>> +			if (next_index == next2) {
>>>> +				to_next[0] = from[2];
>>>> +				to_next++;
>>>> +				held++;
>>>> +			} else {
>>>> +				rte_node_enqueue_x1(graph, node,
>>> next2,
>>>> +						    from[2]);
>>>> +			}
>>>> +
>>>> +			/* Next3 */
>>>> +			if (next_index == next3) {
>>>> +				to_next[0] = from[3];
>>>> +				to_next++;
>>>> +				held++;
>>>> +			} else {
>>>> +				rte_node_enqueue_x1(graph, node,
>>> next3,
>>>> +						    from[3]);
>>>> +			}
>>>> +
>>>> +			from += 4;
>>>> +
>>>> +		} else {
>>>> +			last_spec += 4;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	while (n_left_from > 0) {
>>>> +		uint32_t next_hop;
>>>> +
>>>> +		mbuf0 = pkts[0];
>>>> +
>>>> +		pkts += 1;
>>>> +		n_left_from -= 1;
>>>> +
>>>> +		/* Extract DIP of mbuf0 */
>>>> +		eth_hdr = rte_pktmbuf_mtod(mbuf0, struct
>>> rte_ether_hdr *);
>>>> +		ipv4_hdr = (struct rte_ipv4_hdr *)(eth_hdr + 1);
>>>> +		/* Extract cksum, ttl as ipv4 hdr is in cache */
>>>> +		rte_node_mbuf_priv1(mbuf0)->cksum = ipv4_hdr-
>>>> hdr_checksum;
>>>> +		rte_node_mbuf_priv1(mbuf0)->ttl = ipv4_hdr-
>>>> time_to_live;
>>>> +
>>>> +		rc = rte_lpm_lookup(lpm, rte_be_to_cpu_32(ipv4_hdr-
>>>> dst_addr),
>>>> +				    &next_hop);
>>>> +		next_hop = (rc == 0) ? next_hop : drop_nh;
>>>> +
>>>> +		rte_node_mbuf_priv1(mbuf0)->nh = next_hop &
>>> 0xFFFF;
>>>> +		next0 = (next_hop >> 16);
>>>> +
>>>> +		if (unlikely(next_index ^ next0)) {
>>>> +			/* Copy things successfully speculated till now
>>> */
>>>> +			rte_memcpy(to_next, from, last_spec *
>>> sizeof(from[0]));
>>>> +			from += last_spec;
>>>> +			to_next += last_spec;
>>>> +			held += last_spec;
>>>> +			last_spec = 0;
>>>> +
>>>> +			rte_node_enqueue_x1(graph, node, next0,
>>> from[0]);
>>>> +			from += 1;
>>>> +		} else {
>>>> +			last_spec += 1;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	/* !!! Home run !!! */
>>>> +	if (likely(last_spec == nb_objs)) {
>>>> +		rte_node_next_stream_move(graph, node,
>>> next_index);
>>>> +		return nb_objs;
>>>> +	}
>>>> +
>>>> +	held += last_spec;
>>>> +	/* Copy things successfully speculated till now */
>>>> +	rte_memcpy(to_next, from, last_spec * sizeof(from[0]));
>>>> +	rte_node_next_stream_put(graph, node, next_index, held);
>>>> +
>>>> +	return nb_objs;
>>>> +}
>>>> +
>>>>  #else
>>>>
>>>>  static uint16_t
>>>>