[PATCH net v2 8/9] selftests: drv-net: pp_alloc_fail: lower traffic expectations

[Jakub Kicinski <kuba@kernel.org>]

Lower the expected level of traffic in the pp_alloc_fail test
and calculate failure counter thresholds based on the traffic
rather than using a fixed constant.

We only have "QEMU HW" in NIPA right now, and the test (due to
debug dependencies) only works on debug kernels in the first place.
We need some place for it to pass otherwise it seems to be bit
rotting. So lower the traffic threshold so that it passes on QEMU
and with a debug kernel...

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - use seen_fails in 2 more places

CC: shuah@kernel.org
CC: johndale@cisco.com
CC: linux-kselftest@vger.kernel.org
---
 .../selftests/drivers/net/hw/pp_alloc_fail.py    | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/hw/pp_alloc_fail.py b/tools/testing/selftests/drivers/net/hw/pp_alloc_fail.py
index fc66b7a7b149..2a51b60df8a1 100755
--- a/tools/testing/selftests/drivers/net/hw/pp_alloc_fail.py
+++ b/tools/testing/selftests/drivers/net/hw/pp_alloc_fail.py
@@ -7,6 +7,7 @@ Test driver resilience vs page pool allocation failures.
 
 import errno
 import time
+import math
 import os
 from lib.py import ksft_run, ksft_exit, ksft_pr
 from lib.py import KsftSkipEx, KsftFailEx
@@ -62,7 +63,7 @@ from lib.py import cmd, tool, GenerateTraffic
         stat1 = get_stats()
         time.sleep(1)
         stat2 = get_stats()
-        if stat2['rx-packets'] - stat1['rx-packets'] < 15000:
+        if stat2['rx-packets'] - stat1['rx-packets'] < 4000:
             raise KsftFailEx("Traffic seems low:", stat2['rx-packets'] - stat1['rx-packets'])
 
 
@@ -89,11 +90,16 @@ from lib.py import cmd, tool, GenerateTraffic
         time.sleep(3)
         s2 = get_stats()
 
-        if s2['rx-alloc-fail'] - s1['rx-alloc-fail'] < 1:
+        seen_fails = s2['rx-alloc-fail'] - s1['rx-alloc-fail']
+        if seen_fails < 1:
             raise KsftSkipEx("Allocation failures not increasing")
-        if s2['rx-alloc-fail'] - s1['rx-alloc-fail'] < 100:
-            raise KsftSkipEx("Allocation increasing too slowly", s2['rx-alloc-fail'] - s1['rx-alloc-fail'],
-                             "packets:", s2['rx-packets'] - s1['rx-packets'])
+        pkts = s2['rx-packets'] - s1['rx-packets']
+        # Expecting one failure per 512 buffers, 3.1x safety margin
+        want_fails = math.floor(pkts / 512 / 3.1)
+        if seen_fails < want_fails:
+            raise KsftSkipEx("Allocation increasing too slowly", seen_fails,
+                             "packets:", pkts)
+        ksft_pr(f"Seen: pkts:{pkts} fails:{seen_fails} (pass thrs:{want_fails})")
 
         # Basic failures are fine, try to wobble some settings to catch extra failures
         check_traffic_flowing()
-- 
2.51.0