[PATCH net-next 1/2] selftests: drv-net: rss_ctx: use Netlink for timed reconfig

[Jakub Kicinski <kuba@kernel.org>]

The rss_ctx test has gotten pretty flaky after I increased
the queue count in NIPA 2->3. Not 100% clear why. We get
a lot of failures in the rss_ctx.test_hitless_key_update case.

Looking closer it appears that the failures are mostly due
to startup costs. I measured the following timing for ethtool -X:
 - python cmd(shell=True)  : 150-250msec
 - python cmd(shell=False) :  50- 70msec
 - timed in bash           :  45- 55msec
 - YNL Netlink call        :   2-  4msec
 - .set_rxfh callback      :   1-  2msec

The target in the test was set to 200msec. We were mostly measuring
ethtool startup cost it seems. Switch to YNL since it's 100x faster.

Lower the pass criteria to ~75msec, no real science behind this number
but we removed ~150msec of overhead, and the old target was 200msec.
So any driver that was passing previously should still pass with 75msec.

Separately we should probably follow up on defaulting to shell=False,
when script doesn't explicitly ask for True, because the overhead
is rather significant.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/testing/selftests/drivers/net/hw/rss_ctx.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/drivers/net/hw/rss_ctx.py b/tools/testing/selftests/drivers/net/hw/rss_ctx.py
index 9838b8457e5a..3fc5688605b5 100755
--- a/tools/testing/selftests/drivers/net/hw/rss_ctx.py
+++ b/tools/testing/selftests/drivers/net/hw/rss_ctx.py
@@ -335,19 +335,20 @@ from lib.py import ethtool, ip, defer, GenerateTraffic, CmdExitFailure
     data = get_rss(cfg)
     key_len = len(data['rss-hash-key'])
 
-    key = _rss_key_rand(key_len)
+    ethnl = EthtoolFamily()
+    key = random.randbytes(key_len)
 
     tgen = GenerateTraffic(cfg)
     try:
         errors0, carrier0 = get_drop_err_sum(cfg)
         t0 = datetime.datetime.now()
-        ethtool(f"-X {cfg.ifname} hkey " + _rss_key_str(key))
+        ethnl.rss_set({"header": {"dev-index": cfg.ifindex}, "hkey": key})
         t1 = datetime.datetime.now()
         errors1, carrier1 = get_drop_err_sum(cfg)
     finally:
         tgen.wait_pkts_and_stop(5000)
 
-    ksft_lt((t1 - t0).total_seconds(), 0.2)
+    ksft_lt((t1 - t0).total_seconds(), 0.075)
     ksft_eq(errors1 - errors1, 0)
     ksft_eq(carrier1 - carrier0, 0)
 
-- 
2.51.0