netdev - [PATCH net-next 4/5] selftests: mlxsw: sch_red_core: Send more packets for drop tests

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Message-ID: <abc869b9f6003d400d6293ddd5edb2f4517f44d5.1728316370.git.petrm@nvidia.com>
Date: Mon, 7 Oct 2024 18:26:08 +0200
From: Petr Machata <petrm@...dia.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <netdev@...r.kernel.org>
CC: Amit Cohen <amcohen@...dia.com>, Ido Schimmel <idosch@...dia.com>,
	<linux-kselftest@...r.kernel.org>, Shuah Khan <shuah@...nel.org>, "Petr
 Machata" <petrm@...dia.com>, <mlxsw@...dia.com>
Subject: [PATCH net-next 4/5] selftests: mlxsw: sch_red_core: Send more packets for drop tests

This test works by injecting into a port with a maxed-out queue a couple
packets and checks if a corresponding number of packets were dropped. This
has worked well on Spectrum<4, but on Spectrum-4 it has been noisy. This
is in line with the observation that on Spectrum-4, queue size tends to
fluctuate more. A handful of packets could then still be accepted to the
queue even though it was nominally full just recently.

In order to accommodate this behavior, send many more packets. The buffer
can fit N extra packets, but not N% packets. This therefore allows us to
set wider absolute margins, while actually narrowing them relatively.

Signed-off-by: Petr Machata <petrm@...dia.com>
Reviewed-by: Ido Schimmel <idosch@...dia.com>
---
 .../selftests/drivers/net/mlxsw/sch_red_core.sh  | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

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 b1ff395b3880..316444389c4e 100644
--- a/tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh
+++ b/tools/testing/selftests/drivers/net/mlxsw/sch_red_core.sh
@@ -653,20 +653,22 @@ do_drop_test()
 	build_backlog $vlan $((3 * limit / 2)) udp >/dev/null
 
 	base=$($fetch_counter)
-	send_packets $vlan udp 11
+	send_packets $vlan udp 100
 
-	now=$(busywait 1100 until_counter_is ">= $((base + 10))" $fetch_counter)
-	check_err $? "Dropped packets not observed: 11 expected, $((now - base)) seen"
+	now=$(busywait 1100 until_counter_is ">= $((base + 95))" $fetch_counter)
+	check_err $? "${trigger}ped packets not observed: 100 expected, $((now - base)) seen"
 
 	# When no extra traffic is injected, there should be no mirroring.
-	busywait 1100 until_counter_is ">= $((base + 20))" $fetch_counter >/dev/null
+	busywait 1100 until_counter_is ">= $((base + 110))" \
+		 $fetch_counter >/dev/null
 	check_fail $? "Spurious packets observed"
 
 	# When the rule is uninstalled, there should be no mirroring.
 	qevent_rule_uninstall_$subtest
-	send_packets $vlan udp 11
-	busywait 1100 until_counter_is ">= $((base + 20))" $fetch_counter >/dev/null
-	check_fail $? "Spurious packets observed after uninstall"
+	send_packets $vlan udp 100
+	now=$(busywait 1100 until_counter_is ">= $((base + 110))" \
+		       $fetch_counter)
+	check_fail $? "$((now - base)) spurious packets observed after uninstall"
 
 	log_test "TC $((vlan - 10)): ${trigger}ped packets $subtest'd"
 
-- 
2.45.0