samples/net/zperf/overlay-loopback-icount.conf - third_party/github/zephyrproject-rtos/zephyr - Git at Google

 # Deterministic, host-speed-independent zperf throughput measurement.
 #
 # Layer this on top of overlay-loopback.conf, e.g.:
 #   -DEXTRA_CONF_FILE="overlay-loopback.conf;overlay-loopback-icount.conf"
 #
 # All traffic stays inside the guest (loopback), so QEMU icount mode can be
 # safely enabled. In icount mode the virtual CPU advances virtual time by
 # 2^SHIFT ns per executed instruction, so the reported throughput becomes a
 # deterministic function of instructions-per-byte instead of host wall clock.

 # Force QEMU icount on. It is disabled by default when networking + shell are
 # enabled, but with loopback-only traffic there is no real host I/O in the
 # measurement path.
 CONFIG_QEMU_ICOUNT=y
 CONFIG_QEMU_ICOUNT_SHIFT=5
 CONFIG_QEMU_ICOUNT_SLEEP=n

 # icount only works with a single CPU.
 CONFIG_MP_MAX_NUM_CPUS=1

 # Run the kernel tick at 10 kHz. The default qemu_x86 rate is 100 Hz, which
 # (a) compiles in the UDP uploader's clock-compensation path that divides by
 # the per-packet duration - a division by zero once the unlimited rate drives
 # that duration to 0 - and (b) is far too coarse to pace traffic. A >1 kHz tick
 # removes the compensation path and gives fine-grained timing.
 CONFIG_SYS_CLOCK_TICKS_PER_SEC=10000

 # Loopback-only: no QEMU SLIP/TAP host networking. This removes the external,
 # real-time network backend that would otherwise make icount non-deterministic
 # (and require a host-side slip.sock).
 CONFIG_NET_QEMU_SLIP=n
 CONFIG_NET_SLIP_TAP=n

 # Self-driven loopback runner (see src/main.c). Avoids the interactive shell,
 # which can stall under icount waiting on real-time stdin.
 CONFIG_ZPERF_LOOPBACK_SELFTEST=y

 # The UDP uploader needs a receive timeout to collect the server statistics.
 CONFIG_NET_CONTEXT_RCVTIMEO=y

 # The zperf receivers register several sockets with the socket service; give
 # zvfs_poll() enough slots for the TCP listener plus its sessions.
 CONFIG_ZVFS_POLL_MAX=16

 # The loopback driver delivers each packet synchronously in the sender's
 # context, so the whole receive path (and, for this sample, the blocking client
 # upload) runs on the caller's stack. Give the involved threads generous stacks
 # to absorb that nesting; otherwise the guest overflows and faults at boot.
 CONFIG_MAIN_STACK_SIZE=3072
 CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2560
 CONFIG_NET_RX_STACK_SIZE=2560
 CONFIG_NET_TX_STACK_SIZE=2560
 CONFIG_NET_MGMT_EVENT_STACK_SIZE=2560
 CONFIG_NET_SOCKETS_SERVICE_STACK_SIZE=2560

 # Do not try to add IPv4/6 address to network interface but let the system
 # use the localhost addresses.
 CONFIG_NET_CONFIG_MY_IPV4_ADDR=""
 CONFIG_NET_CONFIG_MY_IPV6_ADDR=""

 # Disable statistics so that the stats collection will not lower the numbers.
 CONFIG_NET_STATISTICS=n

 # Push near-MTU-sized frames through the stack so the per-packet cost is
 # dominated by data-touching work (checksums, buffer/fragment walking) rather
 # than fixed per-call overhead. The selftest sends a 1220 byte payload (see the
 # Kconfig default): that is the IPv6 TCP MSS at a 1280 byte MTU (1280 - 40 IPv6
 # - 20 TCP), so every TCP write is a single full-sized segment for both IPv4 and
 # IPv6 (avoiding a tiny trailing segment that would otherwise halve IPv6 TCP),
 # and the UDP datagrams stay under the MTU for both families so no IP
 # fragmentation is needed. Raise the loopback L3 MTU accordingly and lift
 # zperf's own packet ceiling above the (larger, fragmenting) payload below.
 CONFIG_NET_LOOPBACK_MTU=1280
 CONFIG_NET_ZPERF_MAX_PACKET_SIZE=2100

 # Keep the net_buf data size (1100, from overlay-loopback.conf) below the MTU so
 # each 1280 byte packet spans two buffer fragments. This deliberately exercises
 # the fragment-chain walk in net_pkt_get_len() and friends.

 # Exercise the IP fragmentation + reassembly subsystem: the runner adds an extra
 # UDP run per family whose payload (see ZPERF_LOOPBACK_SELFTEST_FRAG_PACKET_SIZE)
 # exceeds the MTU, so ipv4.c/ipv6.c must fragment on TX and reassemble on RX.
 CONFIG_NET_IPV4_FRAGMENT=y
 CONFIG_NET_IPV6_FRAGMENT=y

 # Exercise traffic classes and SO_PRIORITY: with more than one TX/RX queue the
 # stack routes prioritised traffic through dedicated per-traffic-class threads
 # (net_tc.c) instead of the caller's context. The runner sets a non-default
 # priority on every upload so this path is always taken.
 CONFIG_NET_TC_TX_COUNT=2
 CONFIG_NET_TC_RX_COUNT=2
 CONFIG_NET_CONTEXT_PRIORITY=y
 CONFIG_NET_ALLOW_ANY_PRIORITY=y
	# Deterministic, host-speed-independent zperf throughput measurement.
	#
	# Layer this on top of overlay-loopback.conf, e.g.:
	# -DEXTRA_CONF_FILE="overlay-loopback.conf;overlay-loopback-icount.conf"
	#
	# All traffic stays inside the guest (loopback), so QEMU icount mode can be
	# safely enabled. In icount mode the virtual CPU advances virtual time by
	# 2^SHIFT ns per executed instruction, so the reported throughput becomes a
	# deterministic function of instructions-per-byte instead of host wall clock.

	# Force QEMU icount on. It is disabled by default when networking + shell are
	# enabled, but with loopback-only traffic there is no real host I/O in the
	# measurement path.
	CONFIG_QEMU_ICOUNT=y
	CONFIG_QEMU_ICOUNT_SHIFT=5
	CONFIG_QEMU_ICOUNT_SLEEP=n

	# icount only works with a single CPU.
	CONFIG_MP_MAX_NUM_CPUS=1

	# Run the kernel tick at 10 kHz. The default qemu_x86 rate is 100 Hz, which
	# (a) compiles in the UDP uploader's clock-compensation path that divides by
	# the per-packet duration - a division by zero once the unlimited rate drives
	# that duration to 0 - and (b) is far too coarse to pace traffic. A >1 kHz tick
	# removes the compensation path and gives fine-grained timing.
	CONFIG_SYS_CLOCK_TICKS_PER_SEC=10000

	# Loopback-only: no QEMU SLIP/TAP host networking. This removes the external,
	# real-time network backend that would otherwise make icount non-deterministic
	# (and require a host-side slip.sock).
	CONFIG_NET_QEMU_SLIP=n
	CONFIG_NET_SLIP_TAP=n

	# Self-driven loopback runner (see src/main.c). Avoids the interactive shell,
	# which can stall under icount waiting on real-time stdin.
	CONFIG_ZPERF_LOOPBACK_SELFTEST=y

	# The UDP uploader needs a receive timeout to collect the server statistics.
	CONFIG_NET_CONTEXT_RCVTIMEO=y

	# The zperf receivers register several sockets with the socket service; give
	# zvfs_poll() enough slots for the TCP listener plus its sessions.
	CONFIG_ZVFS_POLL_MAX=16

	# The loopback driver delivers each packet synchronously in the sender's
	# context, so the whole receive path (and, for this sample, the blocking client
	# upload) runs on the caller's stack. Give the involved threads generous stacks
	# to absorb that nesting; otherwise the guest overflows and faults at boot.
	CONFIG_MAIN_STACK_SIZE=3072
	CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2560
	CONFIG_NET_RX_STACK_SIZE=2560
	CONFIG_NET_TX_STACK_SIZE=2560
	CONFIG_NET_MGMT_EVENT_STACK_SIZE=2560
	CONFIG_NET_SOCKETS_SERVICE_STACK_SIZE=2560

	# Do not try to add IPv4/6 address to network interface but let the system
	# use the localhost addresses.
	CONFIG_NET_CONFIG_MY_IPV4_ADDR=""
	CONFIG_NET_CONFIG_MY_IPV6_ADDR=""

	# Disable statistics so that the stats collection will not lower the numbers.
	CONFIG_NET_STATISTICS=n

	# Push near-MTU-sized frames through the stack so the per-packet cost is
	# dominated by data-touching work (checksums, buffer/fragment walking) rather
	# than fixed per-call overhead. The selftest sends a 1220 byte payload (see the
	# Kconfig default): that is the IPv6 TCP MSS at a 1280 byte MTU (1280 - 40 IPv6
	# - 20 TCP), so every TCP write is a single full-sized segment for both IPv4 and
	# IPv6 (avoiding a tiny trailing segment that would otherwise halve IPv6 TCP),
	# and the UDP datagrams stay under the MTU for both families so no IP
	# fragmentation is needed. Raise the loopback L3 MTU accordingly and lift
	# zperf's own packet ceiling above the (larger, fragmenting) payload below.
	CONFIG_NET_LOOPBACK_MTU=1280
	CONFIG_NET_ZPERF_MAX_PACKET_SIZE=2100

	# Keep the net_buf data size (1100, from overlay-loopback.conf) below the MTU so
	# each 1280 byte packet spans two buffer fragments. This deliberately exercises
	# the fragment-chain walk in net_pkt_get_len() and friends.

	# Exercise the IP fragmentation + reassembly subsystem: the runner adds an extra
	# UDP run per family whose payload (see ZPERF_LOOPBACK_SELFTEST_FRAG_PACKET_SIZE)
	# exceeds the MTU, so ipv4.c/ipv6.c must fragment on TX and reassemble on RX.
	CONFIG_NET_IPV4_FRAGMENT=y
	CONFIG_NET_IPV6_FRAGMENT=y

	# Exercise traffic classes and SO_PRIORITY: with more than one TX/RX queue the
	# stack routes prioritised traffic through dedicated per-traffic-class threads
	# (net_tc.c) instead of the caller's context. The runner sets a non-default
	# priority on every upload so this path is always taken.
	CONFIG_NET_TC_TX_COUNT=2
	CONFIG_NET_TC_RX_COUNT=2
	CONFIG_NET_CONTEXT_PRIORITY=y
	CONFIG_NET_ALLOW_ANY_PRIORITY=y