app/testpmd: fix packet throughput after stats reset

Testpmd calculates packet throughput by getting a diff of previous stats
value and current one.

If a stats clear called after previous sample taken, the diff will be
negative and throughput calculation will be wrong.

If current stats value is smaller than previous one, set throughput to
zero.

Fixes: 0e106980301d ("app/testpmd: show throughput in port stats")
Cc: stable@dpdk.org
Signed-off-by: Wei Zhao <wei.zhao1@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c
index ca83eef99cb1af4ca21d9b3b03edcb9671e62268..e8e311cb548befca7a508187cc2c0b20b2ac06f0 100644 (file)
--- a/app/test-pmd/config.c
+++ b/app/test-pmd/config.c
@@ -203,8 +203,10 @@ nic_stats_display(portid_t port_id)
        if (diff_cycles > 0)
                diff_cycles = prev_cycles[port_id] - diff_cycles;
 
-       diff_pkts_rx = stats.ipackets - prev_pkts_rx[port_id];
-       diff_pkts_tx = stats.opackets - prev_pkts_tx[port_id];
+       diff_pkts_rx = (stats.ipackets > prev_pkts_rx[port_id]) ?
+               (stats.ipackets - prev_pkts_rx[port_id]) : 0;
+       diff_pkts_tx = (stats.opackets > prev_pkts_tx[port_id]) ?
+               (stats.opackets - prev_pkts_tx[port_id]) : 0;
        prev_pkts_rx[port_id] = stats.ipackets;
        prev_pkts_tx[port_id] = stats.opackets;
        mpps_rx = diff_cycles > 0 ?