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[net-next,3/5] selftests: mlxsw: sch_red_core: Sleep before querying queue depth

Message ID 321dcf8b3e9a1f0766429c8cf3e3f1746f1bc375.1728316370.git.petrm@nvidia.com
State New
Headers show
Series selftests: mlxsw: Stabilize RED tests | expand

Commit Message

Petr Machata Oct. 7, 2024, 4:26 p.m. UTC 
The qdisc stats are taken from the port's periodic HW stats, which are
updated once a second. We try to accommodate the latency by using busywait
in build_backlog().

The issue in that seems to be that when do_mark_test() builds the backlog,
it makes the decision whether to send more packets based on the first
instance of the queue depth stat exceeding the current value, when in fact
more traffic is on the way and the queue depth would increase further. This
leads to failures in TC 1 of mark-mirror test, where we see the following
failure:

TEST: TC 0: marked packets mirror'd                                 [ OK ]
TEST: TC 1: marked packets mirror'd                                 [FAIL]
        Spurious packets (1680 -> 2290) observed without buffer pressure

Fix by waiting for the full second before reading the queue depth for the
first time, to make sure it reflects all in-flight traffic.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
---
 tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh | 1 +
 1 file changed, 1 insertion(+)
diff mbox series

Patch

diff --git a/tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh b/tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh
index a25a15eb6d31..b1ff395b3880 100644
--- a/tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh
+++ b/tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh
@@ -372,6 +372,7 @@  build_backlog()
 	local i=0
 
 	while :; do
+		sleep 1
 		local cur=$(busywait 1100 until_counter_is "> $cur" \
 					    get_qdisc_backlog $vlan)
 		local diff=$((size - cur))