Breno Leitao wrote:
Add a basic selftest for the netpoll polling mechanism, specifically targeting the netpoll poll() side.
The test creates a scenario where network transmission is running at maximum sppend, and netpoll needs to poll the NIC. This is achieved by:
minor type: sppend/speed
- Configuring a single RX/TX queue to create contention
- Generating background traffic to saturate the interface
- Sending netconsole messages to trigger netpoll polling
- Using dynamic netconsole targets via configfs
The test validates a critical netpoll code path by monitoring traffic flow and ensuring netpoll_poll_dev() is called when the normal TX path is blocked. Perf probing confirms this test successfully triggers netpoll_poll_dev() in typical test runs.
So the test needs profiling to make it a pass/fail regression test? Then perhaps add it to TEST_FILES rather than TEST_PROGS. Unless exercising the code on its own is valuable enough.
Or is there another way that the packets could be observed, e.g., counters.
This addresses a gap in netpoll test coverage for a path that is tricky for the network stack.
Signed-off-by: Breno Leitao leitao@debian.org
Sending as an RFC for your appreciation, but it dpends on [1] which is stil under review. Once [1] lands, I will send this officially.
Link: https://lore.kernel.org/all/20250611-netdevsim_stat-v1-0-c11b657d96bf@debian... [1]
tools/testing/selftests/drivers/net/Makefile | 1 + .../testing/selftests/drivers/net/netpoll_basic.py | 201 +++++++++++++++++++++ 2 files changed, 202 insertions(+)
diff --git a/tools/testing/selftests/drivers/net/Makefile b/tools/testing/selftests/drivers/net/Makefile index be780bcb73a3b..70d6e3a920b7f 100644 --- a/tools/testing/selftests/drivers/net/Makefile +++ b/tools/testing/selftests/drivers/net/Makefile @@ -15,6 +15,7 @@ TEST_PROGS := \ netcons_fragmented_msg.sh \ netcons_overflow.sh \ netcons_sysdata.sh \
- netpoll_basic.py \ ping.py \ queues.py \ stats.py \
diff --git a/tools/testing/selftests/drivers/net/netpoll_basic.py b/tools/testing/selftests/drivers/net/netpoll_basic.py new file mode 100755 index 0000000000000..8abdfb2b1eb6e --- /dev/null +++ b/tools/testing/selftests/drivers/net/netpoll_basic.py @@ -0,0 +1,201 @@ +#!/usr/bin/env python3 +# SPDX-License-Identifier: GPL-2.0
+# This test aims to evaluate the netpoll polling mechanism (as in netpoll_poll_dev()). +# It presents a complex scenario where the network attempts to send a packet but fails, +# prompting it to poll the NIC from within the netpoll TX side. +# +# This has been a crucial path in netpoll that was previously untested. Jakub +# suggested using a single RX/TX queue, pushing traffic to the NIC, and then sending +# netpoll messages (via netconsole) to trigger the poll. `perf` probing of netpoll_poll_dev() +# showed that this test indeed triggers netpoll_poll_dev() once or twice in 10 iterations.
+# Author: Breno Leitao leitao@debian.org
+import errno +import os +import random +import string +import time
+from lib.py import (
- ethtool,
- GenerateTraffic,
- ksft_exit,
- ksft_pr,
- ksft_run,
- KsftFailEx,
- KsftSkipEx,
- NetdevFamily,
- NetDrvEpEnv,
+)
+NETCONSOLE_CONFIGFS_PATH = "/sys/kernel/config/netconsole" +REMOTE_PORT = 6666 +LOCAL_PORT = 1514 +# Number of netcons messages to send. I usually see netpoll_poll_dev() +# being called at least once in 10 iterations. +ITERATIONS = 10
Is usually sufficient to avoid flakiness, or should this be cranked up?
+DEBUG = False
+def generate_random_netcons_name() -> str:
- """Generate a random name starting with 'netcons'"""
- random_suffix = "".join(random.choices(string.ascii_lowercase + string.digits, k=8))
- return f"netcons_{random_suffix}"
+def get_stats(cfg: NetDrvEpEnv, netdevnl: NetdevFamily) -> dict[str, int]:
- """Get the statistics for the interface"""
- return netdevnl.qstats_get({"ifindex": cfg.ifindex}, dump=True)[0]
+def set_single_rx_tx_queue(interface_name: str) -> None:
- """Set the number of RX and TX queues to 1 using ethtool"""
- try:
# This don't need to be reverted, since interfaces will be deleted after testethtool(f"-G {interface_name} rx 1 tx 1")- except Exception as e:
raise KsftSkipEx(f"Failed to configure RX/TX queues: {e}. Ethtool not available?")+def create_netconsole_target(
- config_data: dict[str, str],
- target_name: str,
+) -> None:
- """Create a netconsole dynamic target against the interfaces"""
- ksft_pr(f"Using netconsole name: {target_name}")
- try:
ksft_pr(f"Created target directory: {NETCONSOLE_CONFIGFS_PATH}/{target_name}")os.makedirs(f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}", exist_ok=True)- except OSError as e:
if e.errno != errno.EEXIST:raise KsftFailEx(f"Failed to create netconsole target directory: {e}")- try:
for key, value in config_data.items():if DEBUG:ksft_pr(f"Setting {key} to {value}")with open(f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}/{key}","w",encoding="utf-8",) as f:# Always convert to string to write to filef.write(str(value))f.close()if DEBUG:# Read all configuration values for debuggingfor debug_key in config_data.keys():with open(f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}/{debug_key}","r",encoding="utf-8",) as f:content = f.read()ksft_pr(f"{NETCONSOLE_CONFIGFS_PATH}/{target_name}/{debug_key} {content}")- except Exception as e:
raise KsftFailEx(f"Failed to configure netconsole target: {e}")+def set_netconsole(cfg: NetDrvEpEnv, interface_name: str, target_name: str) -> None:
- """Configure netconsole on the interface with the given target name"""
- config_data = {
"extended": "1","dev_name": interface_name,"local_port": LOCAL_PORT,"remote_port": REMOTE_PORT,"local_ip": cfg.addr_v["4"] if cfg.addr_ipver == "4" else cfg.addr_v["6"],"remote_ip": (cfg.remote_addr_v["4"] if cfg.addr_ipver == "4" else cfg.remote_addr_v["6"]),"remote_mac": "00:00:00:00:00:00", # Not important for this test"enabled": "1",- }
- create_netconsole_target(config_data, target_name)
- ksft_pr(f"Created netconsole target: {target_name} on interface {interface_name}")
+def delete_netconsole_target(name: str) -> None:
- """Delete a netconsole dynamic target"""
- target_path = f"{NETCONSOLE_CONFIGFS_PATH}/{name}"
- try:
if os.path.exists(target_path):os.rmdir(target_path)- except OSError as e:
raise KsftFailEx(f"Failed to delete netconsole target: {e}")+def check_traffic_flowing(cfg: NetDrvEpEnv, netdevnl: NetdevFamily) -> int:
- """Check if traffic is flowing on the interface"""
- stat1 = get_stats(cfg, netdevnl)
- time.sleep(1)
Can the same be learned with sufficient precision when sleeping for only 100 msec? As tests are added, it's worth trying to keep their runtime short.
- stat2 = get_stats(cfg, netdevnl)
- pkts_per_sec = stat2["rx-packets"] - stat1["rx-packets"]
- # Just make sure this will not fail even in slow/debug kernels
- if pkts_per_sec < 10:
raise KsftFailEx(f"Traffic seems low: {pkts_per_sec}")- if DEBUG:
ksft_pr(f"Traffic per second {pkts_per_sec} ", pkts_per_sec)- return pkts_per_sec
+def do_netpoll_flush(cfg: NetDrvEpEnv, netdevnl: NetdevFamily) -> None:
- """Print messages to the console, trying to trigger a netpoll poll"""
- for i in range(int(ITERATIONS)):
pkts_per_s = check_traffic_flowing(cfg, netdevnl)with open("/dev/kmsg", "w", encoding="utf-8") as kmsg:kmsg.write(f"netcons test #{i}: ({pkts_per_s} packets/s)\n")+def test_netpoll(cfg: NetDrvEpEnv, netdevnl: NetdevFamily) -> None:
- """Test netpoll by sending traffic to the interface and then sending netconsole messages to trigger a poll"""
- target_name = generate_random_netcons_name()
- ifname = cfg.dev["ifname"]
- traffic = None
- try:
set_single_rx_tx_queue(ifname)traffic = GenerateTraffic(cfg)check_traffic_flowing(cfg, netdevnl)set_netconsole(cfg, ifname, target_name)do_netpoll_flush(cfg, netdevnl)- finally:
if traffic:traffic.stop()delete_netconsole_target(target_name)+def check_dependencies() -> None:
- """Check if the dependencies are met"""
- if not os.path.exists(NETCONSOLE_CONFIGFS_PATH):
raise KsftSkipEx(f"Directory {NETCONSOLE_CONFIGFS_PATH} does not exist. CONFIG_NETCONSOLE_DYNAMIC might not be set.")+def main() -> None:
- """Main function to run the test"""
- check_dependencies()
- netdevnl = NetdevFamily()
- with NetDrvEpEnv(__file__, nsim_test=True) as cfg:
ksft_run([test_netpoll],args=(cfg,netdevnl,),)- ksft_exit()
+if __name__ == "__main__":
- main()
base-commit: 5d6d67c4cb10a4b4d3ae35758d5eeed6239afdc8 change-id: 20250612-netpoll_test-a1324d2057c8
Best regards,
Breno Leitao leitao@debian.org