Re: [dpdk-dev] [PATCH] app/testpmd: fix Rx/Tx stats after clear stats command

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 4/24/2020 12:07 PM, Wei Hu (Xavier) wrote:
> From: Chengwen Feng <fengchengwen@huawei.com>
> 
> Currently, when running start/clear stats&xstats/stop command many times
> based on testpmd application, there are incorrect RX/TX-packets stats as
> below:
> ---------------------- Forward statistics for port 0  --------------
> RX-packets: 18446744073709544808 RX-dropped: 0             ...ignore
> TX-packets: 18446744073709536616 TX-dropped: 0             ...ignore
> --------------------------------------------------------------------
> 
> The root cause as below:
> 1. The struct rte_port of testpmd.h has a member variable
>    "struct rte_eth_stats stats" to store the last port statistics.
> 2. When runnig start command, it execute cmd_start_parsed ->
>    start_packet_forwarding -> fwd_stats_reset, which call rte_eth_stats_get
>    API function to save current port statistics.
> 3. When running stop command, it execute fwd_stats_display, which call
>    rte_eth_stats_get to get current port statistics, and then minus last
>    port statistics.
> 4. If we run clear stats or xstats after start command, then run stop,
>    it may display above incorrect stats because the current Rx/Tx-packets
>    is lower than the last saved RX/TX-packets(uint64_t overflow).

Looks like valid issue.

Can you please update the title to mention this fixes the forward stats (to
prevent the misunderstanding that issue is in the port stats).

Also can you please update the documentation
(doc/guides/testpmd_app_ug/testpmd_funcs.rst), "clear port" command to say this
will also affect the forward stats output (show fwd)?

> 
> This patch fixes it by clearing last port statistics when executing
> "clear stats/xstats" command.
> 
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
> ---
>  app/test-pmd/config.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
> index 72f25d152..0d2375607 100644
> --- a/app/test-pmd/config.c
> +++ b/app/test-pmd/config.c
> @@ -234,10 +234,16 @@ nic_stats_display(portid_t port_id)
>  void
>  nic_stats_clear(portid_t port_id)
>  {
> +	struct rte_port *port;
> +
>  	if (port_id_is_invalid(port_id, ENABLED_WARN)) {
>  		print_valid_ports();
>  		return;
>  	}
> +
> +	port = &ports[port_id];
> +	/* clear last port statistics because eth stats reset */
> +	memset(&port->stats, 0, sizeof(port->stats));

"clear fwd stats" command does same thing in "fwd_stats_reset()" as:
rte_eth_stats_get(pt_id, &ports[pt_id].stats);

I suggest doing same here for consistency, but it should be after
'rte_eth_stats_reset()' in that case.

>  	rte_eth_stats_reset(port_id);
>  	printf("\n  NIC statistics for port %d cleared\n", port_id);
>  }
> @@ -308,12 +314,17 @@ nic_xstats_display(portid_t port_id)
>  void
>  nic_xstats_clear(portid_t port_id)
>  {
> +	struct rte_port *port;
>  	int ret;
>  
>  	if (port_id_is_invalid(port_id, ENABLED_WARN)) {
>  		print_valid_ports();
>  		return;
>  	}
> +
> +	port = &ports[port_id];
> +	/* clear last port statistics because eth xstats(include stats) reset */
> +	memset(&port->stats, 0, sizeof(port->stats));
>  	ret = rte_eth_xstats_reset(port_id);
>  	if (ret != 0) {
>  		printf("%s: Error: failed to reset xstats (port %u): %s",
>