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 > 1. Configuring a single RX/TX queue to create contention > 2. Generating background traffic to saturate the interface > 3. Sending netconsole messages to trigger netpoll polling > 4. 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 <lei...@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-c11b657d9...@debian.org/ > [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 <lei...@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 test > + ethtool(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 file > + f.write(str(value)) > + f.close() > + > + if DEBUG: > + # Read all configuration values for debugging > + for 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 <lei...@debian.org> >
