stress-tests: Improve stressing

*hackbench* doesn't produce much load on a SMP system. A better way to stress
the CPU is copying data from /dev/zero to /dev/null.

Running *du* and *find* doesn't stress Linux very much. Most of it is
optimised through caches. Better: run *dd* to copy the whole block device to
/dev/null.

To stress the network interface (but not your internet connection) send
massive pings to the gateway. In a docker container this might be the system
itself which wouldn't load the NIC. With the environment variable
STRESS_SERVER you can set a different address. The tool *ip* used to find
the gateway is in the package iproute2.

stress-tests/Dockerfile

@@ -4,7 +4,7 @@ ARG IMAGE_TAG=2-bullseye
 FROM --platform=$IMAGE_ARCH torizon/debian:$IMAGE_TAG
 
 RUN apt update \
-    && apt install -y --no-install-recommends iperf3 rt-tests iputils-ping \
+    && apt install -y --no-install-recommends iperf3 rt-tests iputils-ping iproute2 \
     && apt clean \
     && rm -rf /var/lib/apt/lists/*
 

stress-tests/stress-tests.sh

@@ -3,11 +3,14 @@
 echo "Setting up stress tests..."
 
 # CPU load
-while true; do hackbench >/dev/null 2>&1; done &
+for i in $(seq $(nproc)); do dd if=/dev/zero of=/dev/null bs=4M & done
 
-# I/O load (eMMC read)
-while true; do du /usr >/dev/null 2>&1; done &
-while true; do find / -name a* >/dev/null 2>&1; done &
+# I/O read load
+for dev in /dev/mmcblk? /dev/sd?; do
+    test -b "$dev" || continue
+
+    while true; do dd if="$dev" of=/dev/null bs=4M; done &
+done
 
 # I/O load (USB read/write)
 if mount | grep /mnt/pendrive >/dev/null; then
@@ -37,6 +40,9 @@ while true; do
     done
 done &
 
+ping -A -f -t 3 -q -s 49152 \
+    ${STRESS_SERVER:-$(ip route get 1.1.1.1 |sed '/.* via \([^ ]*\) .*/ s//\1/; q')}
+
 echo "RT stress tests started successfully!"
 
 # Dont exit