[v1,2/6] app/test: synchronize statistics between lcores

  Statistics of handled packets are cleared and read on main lcore,
while they are increased in workers handlers on different lcores.

Without synchronization occasionally showed invalid values.
This patch uses atomic acquire/release mechanisms to synchronize.

Fixes: c3eabff124e6 ("distributor: add unit tests")
Cc: bruce.richardson@intel.com
Cc: stable@dpdk.org

Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
---
 app/test/test_distributor.c | 39 ++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)
  

On 15/9/2020 8:34 PM, Lukasz Wojciechowski wrote:
> Statistics of handled packets are cleared and read on main lcore,
> while they are increased in workers handlers on different lcores.
>
> Without synchronization occasionally showed invalid values.
> This patch uses atomic acquire/release mechanisms to synchronize.
>
> Fixes: c3eabff124e6 ("distributor: add unit tests")
> Cc: bruce.richardson@intel.com
> Cc: stable@dpdk.org
>
> Signed-off-by: Lukasz Wojciechowski <l.wojciechow@partner.samsung.com>
> ---
>   app/test/test_distributor.c | 39 ++++++++++++++++++++++++-------------
>   1 file changed, 26 insertions(+), 13 deletions(-)
>
> diff --git a/app/test/test_distributor.c b/app/test/test_distributor.c
> index 35b25463a..0e49e3714 100644
> --- a/app/test/test_distributor.c
> +++ b/app/test/test_distributor.c
> @@ -43,7 +43,8 @@ total_packet_count(void)
>   {
>   	unsigned i, count = 0;
>   	for (i = 0; i < worker_idx; i++)
> -		count += worker_stats[i].handled_packets;
> +		count += __atomic_load_n(&worker_stats[i].handled_packets,
> +				__ATOMIC_ACQUIRE);
>   	return count;
>   }
>   
> @@ -52,6 +53,7 @@ static inline void
>   clear_packet_count(void)
>   {
>   	memset(&worker_stats, 0, sizeof(worker_stats));
> +	rte_atomic_thread_fence(__ATOMIC_RELEASE);
>   }
>   
>   /* this is the basic worker function for sanity test
> @@ -72,13 +74,13 @@ handle_work(void *arg)
>   	num = rte_distributor_get_pkt(db, id, buf, buf, num);
>   	while (!quit) {
>   		__atomic_fetch_add(&worker_stats[id].handled_packets, num,
> -				__ATOMIC_RELAXED);
> +				__ATOMIC_ACQ_REL);
>   		count += num;
>   		num = rte_distributor_get_pkt(db, id,
>   				buf, buf, num);
>   	}
>   	__atomic_fetch_add(&worker_stats[id].handled_packets, num,
> -			__ATOMIC_RELAXED);
> +			__ATOMIC_ACQ_REL);
>   	count += num;
>   	rte_distributor_return_pkt(db, id, buf, num);
>   	return 0;
> @@ -134,7 +136,8 @@ sanity_test(struct worker_params *wp, struct rte_mempool *p)
>   
>   	for (i = 0; i < rte_lcore_count() - 1; i++)
>   		printf("Worker %u handled %u packets\n", i,
> -				worker_stats[i].handled_packets);
> +			__atomic_load_n(&worker_stats[i].handled_packets,
> +					__ATOMIC_ACQUIRE));
>   	printf("Sanity test with all zero hashes done.\n");
>   
>   	/* pick two flows and check they go correctly */
> @@ -159,7 +162,9 @@ sanity_test(struct worker_params *wp, struct rte_mempool *p)
>   
>   		for (i = 0; i < rte_lcore_count() - 1; i++)
>   			printf("Worker %u handled %u packets\n", i,
> -					worker_stats[i].handled_packets);
> +				__atomic_load_n(
> +					&worker_stats[i].handled_packets,
> +					__ATOMIC_ACQUIRE));
>   		printf("Sanity test with two hash values done\n");
>   	}
>   
> @@ -185,7 +190,8 @@ sanity_test(struct worker_params *wp, struct rte_mempool *p)
>   
>   	for (i = 0; i < rte_lcore_count() - 1; i++)
>   		printf("Worker %u handled %u packets\n", i,
> -				worker_stats[i].handled_packets);
> +			__atomic_load_n(&worker_stats[i].handled_packets,
> +					__ATOMIC_ACQUIRE));
>   	printf("Sanity test with non-zero hashes done\n");
>   
>   	rte_mempool_put_bulk(p, (void *)bufs, BURST);
> @@ -280,15 +286,17 @@ handle_work_with_free_mbufs(void *arg)
>   		buf[i] = NULL;
>   	num = rte_distributor_get_pkt(d, id, buf, buf, num);
>   	while (!quit) {
> -		worker_stats[id].handled_packets += num;
>   		count += num;
> +		__atomic_fetch_add(&worker_stats[id].handled_packets, num,
> +				__ATOMIC_ACQ_REL);
>   		for (i = 0; i < num; i++)
>   			rte_pktmbuf_free(buf[i]);
>   		num = rte_distributor_get_pkt(d,
>   				id, buf, buf, num);
>   	}
> -	worker_stats[id].handled_packets += num;
>   	count += num;
> +	__atomic_fetch_add(&worker_stats[id].handled_packets, num,
> +			__ATOMIC_ACQ_REL);
>   	rte_distributor_return_pkt(d, id, buf, num);
>   	return 0;
>   }
> @@ -363,8 +371,9 @@ handle_work_for_shutdown_test(void *arg)
>   	/* wait for quit single globally, or for worker zero, wait
>   	 * for zero_quit */
>   	while (!quit && !(id == zero_id && zero_quit)) {
> -		worker_stats[id].handled_packets += num;
>   		count += num;
> +		__atomic_fetch_add(&worker_stats[id].handled_packets, num,
> +				__ATOMIC_ACQ_REL);
>   		for (i = 0; i < num; i++)
>   			rte_pktmbuf_free(buf[i]);
>   		num = rte_distributor_get_pkt(d,
> @@ -379,10 +388,11 @@ handle_work_for_shutdown_test(void *arg)
>   
>   		total += num;
>   	}
> -	worker_stats[id].handled_packets += num;
>   	count += num;
>   	returned = rte_distributor_return_pkt(d, id, buf, num);
>   
> +	__atomic_fetch_add(&worker_stats[id].handled_packets, num,
> +			__ATOMIC_ACQ_REL);
>   	if (id == zero_id) {
>   		/* for worker zero, allow it to restart to pick up last packet
>   		 * when all workers are shutting down.
> @@ -394,10 +404,11 @@ handle_work_for_shutdown_test(void *arg)
>   				id, buf, buf, num);
>   
>   		while (!quit) {
> -			worker_stats[id].handled_packets += num;
>   			count += num;
>   			rte_pktmbuf_free(pkt);
>   			num = rte_distributor_get_pkt(d, id, buf, buf, num);
> +			__atomic_fetch_add(&worker_stats[id].handled_packets,
> +					num, __ATOMIC_ACQ_REL);
>   		}
>   		returned = rte_distributor_return_pkt(d,
>   				id, buf, num);
> @@ -461,7 +472,8 @@ sanity_test_with_worker_shutdown(struct worker_params *wp,
>   
>   	for (i = 0; i < rte_lcore_count() - 1; i++)
>   		printf("Worker %u handled %u packets\n", i,
> -				worker_stats[i].handled_packets);
> +			__atomic_load_n(&worker_stats[i].handled_packets,
> +					__ATOMIC_ACQUIRE));
>   
>   	if (total_packet_count() != BURST * 2) {
>   		printf("Line %d: Error, not all packets flushed. "
> @@ -514,7 +526,8 @@ test_flush_with_worker_shutdown(struct worker_params *wp,
>   	zero_quit = 0;
>   	for (i = 0; i < rte_lcore_count() - 1; i++)
>   		printf("Worker %u handled %u packets\n", i,
> -				worker_stats[i].handled_packets);
> +			__atomic_load_n(&worker_stats[i].handled_packets,
> +					__ATOMIC_ACQUIRE));
>   
>   	if (total_packet_count() != BURST) {
>   		printf("Line %d: Error, not all packets flushed. "


Thanks.

Acked-by: David Hunt <david.hunt@intel.com>