[RFC net-next v2 5/5] selftests: drv-net: measure devmem performance with kperf

[Stanislav Fomichev <sdf.kernel@gmail.com>]

Add a separate udmabuf-backed devmem performance test using KperfRunner.
Keep correctness cases in drivers/net/hw. Skip the test when kperf or
/dev/udmabuf is missing, and fail it when the kperf run fails.

Example metric output:

  # # ktap-metric-policy-json: {"display_label":"Gbps","name":"throughput","regression":{"better":"higher","compare":"p50","relative_tolerance":0.05},"summarize":"p50"}
  # # ktap-metric-policy-json: {"name":"tcp.retransmits","summarize":"max"}
  # # ktap-metric-json: {"host":"remote","name":"throughput","time":29.786267,"type":"scalar","value":389.29900000000004}
  # # ktap-metric-json: {"host":"remote","name":"tcp.retransmits","time":29.786286,"type":"scalar","value":698}
  # # ktap-metric-json: {"host":"local","name":"throughput","time":29.786289,"type":"scalar","value":388.772}
  # # ktap-metric-json: {"host":"local","name":"tcp.retransmits","time":29.78629,"type":"scalar","value":0}

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
---
 .../drivers/net/hw/performance/Makefile       |  5 +-
 .../drivers/net/hw/performance/config         |  3 +
 .../drivers/net/hw/performance/devmem.py      | 99 +++++++++++++++++++
 3 files changed, 106 insertions(+), 1 deletion(-)
 create mode 100755 tools/testing/selftests/drivers/net/hw/performance/devmem.py

diff --git a/tools/testing/selftests/drivers/net/hw/performance/Makefile b/tools/testing/selftests/drivers/net/hw/performance/Makefile
index 5d53ef548306..27afdace92e6 100644
--- a/tools/testing/selftests/drivers/net/hw/performance/Makefile
+++ b/tools/testing/selftests/drivers/net/hw/performance/Makefile
@@ -1,6 +1,9 @@
 # SPDX-License-Identifier: GPL-2.0
 
-TEST_PROGS := iperf.py
+TEST_PROGS := \
+	devmem.py \
+	iperf.py \
+	#
 
 TEST_INCLUDES := \
 	$(wildcard ../lib/py/*.py ../../lib/py/*.py) \
diff --git a/tools/testing/selftests/drivers/net/hw/performance/config b/tools/testing/selftests/drivers/net/hw/performance/config
index 6450f34933e6..111e9b58610d 100644
--- a/tools/testing/selftests/drivers/net/hw/performance/config
+++ b/tools/testing/selftests/drivers/net/hw/performance/config
@@ -1 +1,4 @@
 CONFIG_IPV6=y
+CONFIG_NET_DEVMEM=y
+CONFIG_SYNC_FILE=y
+CONFIG_UDMABUF=y
diff --git a/tools/testing/selftests/drivers/net/hw/performance/devmem.py b/tools/testing/selftests/drivers/net/hw/performance/devmem.py
new file mode 100755
index 000000000000..033485f926e4
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/hw/performance/devmem.py
@@ -0,0 +1,99 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""Measure udmabuf-backed devmem TCP throughput with kperf."""
+
+from os import path
+import sys
+
+sys.path.insert(0, path.join(path.dirname(path.abspath(__file__)), ".."))
+
+from lib.py import cmd, defer, ethtool, EthtoolFamily, KperfRunner
+from lib.py import ksft_disruptive, ksft_exit, ksft_run, KsftSkipEx
+from lib.py import NetDrvEpEnv
+
+
+UDMABUF_LIMIT = "/sys/module/udmabuf/parameters/size_limit_mb"
+UDMABUF_SIZE_MB = 2048
+
+
+def _set_udmabuf_limit(host) -> None:
+    current = cmd(f"cat {UDMABUF_LIMIT}", host=host).stdout.strip()
+    if int(current) >= UDMABUF_SIZE_MB:
+        return
+
+    cmd(f"echo {UDMABUF_SIZE_MB} > {UDMABUF_LIMIT}", host=host, shell=True)
+    defer(cmd, f"echo {current} > {UDMABUF_LIMIT}", host=host, shell=True)
+
+
+def _enable_hw_gro(cfg) -> None:
+    features = ethtool(f"-k {cfg.ifname}", json=True)[0]
+    hw_gro = features["rx-gro-hw"]
+    if not hw_gro["active"]:
+        if hw_gro["fixed"]:
+            raise KsftSkipEx("Test requires rx-gro-hw support")
+        ethtool(f"-K {cfg.ifname} rx-gro-hw on")
+        defer(ethtool, f"-K {cfg.ifname} rx-gro-hw off")
+
+
+@ksft_disruptive
+def kperf(cfg) -> None:
+    """Measure udmabuf-backed devmem performance with kperf."""
+    runner = KperfRunner(cfg)
+
+    for name, host in (("local", None), ("remote", cfg.remote)):
+        if cmd("test -c /dev/udmabuf", host=host, fail=False).ret:
+            raise KsftSkipEx(f"Test requires /dev/udmabuf on the {name} host")
+        _set_udmabuf_limit(host)
+
+    # kperf reprograms the RSS indirection table for its queues.
+    defer(ethtool, f"-X {cfg.ifname} default")
+
+    _enable_hw_gro(cfg)
+
+    ethnl = EthtoolFamily()
+    rings = ethnl.rings_get({"header": {"dev-index": cfg.ifindex}})
+    restore = {
+        "header": {"dev-index": cfg.ifindex},
+        "tcp-data-split": rings.get("tcp-data-split", "unknown"),
+    }
+    config = {
+        "header": {"dev-index": cfg.ifindex},
+        "tcp-data-split": "enabled",
+    }
+    # Memory providers require a zero threshold where the driver has one.
+    if "hds-thresh" in rings:
+        restore["hds-thresh"] = rings["hds-thresh"]
+        config["hds-thresh"] = 0
+    defer(ethnl.rings_set, restore)
+    ethnl.rings_set(config)
+
+    devmem_args = [
+        "--time", "15",
+        "--num-connections", "4",
+        "--read-size", str(64 << 20),
+        "--write-size", str(64 << 20),
+        "--pin-off", "4",
+        "--num-rx-queues", "4",
+        "--dmabuf-rx-size-mb", str(UDMABUF_SIZE_MB),
+        "--dmabuf-tx-size-mb", str(UDMABUF_SIZE_MB),
+        "--validate", "no",
+        "--devmem-rx",
+        "--devmem-tx",
+        "--devmem-rx-memory", "host",
+        "--devmem-tx-memory", "host",
+    ]
+
+    with runner:
+        runner.run(client_args=devmem_args, report=True)
+
+
+def main() -> None:
+    """Run the devmem performance test."""
+    with NetDrvEpEnv(__file__, nsim_test=False) as cfg:
+        ksft_run([kperf], args=(cfg,))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()
-- 
2.53.0-Meta