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

@@ -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) \

@@ -1 +1,4 @@
 CONFIG_IPV6=y
+CONFIG_NET_DEVMEM=y
+CONFIG_SYNC_FILE=y
+CONFIG_UDMABUF=y

@@ -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()