Re: [PATCH v2 2/2] perf test: Add sched latency and script shell tests

[James Clark <james.clark@linaro.org>]

On 19/06/2025 1:20 am, Ian Rogers wrote:
> Add shell tests covering the `perf sched latency` and `perf sched
> script` commands. The test creates 2 noploop processes on the same
> forced CPU, it then checks that the process appears in the `perf
> sched` output.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
> v2: Skip the test if not root due to permissions.
> ---
>   tools/perf/tests/shell/sched.sh | 91 +++++++++++++++++++++++++++++++++
>   1 file changed, 91 insertions(+)
>   create mode 100755 tools/perf/tests/shell/sched.sh
> 
> diff --git a/tools/perf/tests/shell/sched.sh b/tools/perf/tests/shell/sched.sh
> new file mode 100755
> index 000000000000..0a4fe3f414e1
> --- /dev/null
> +++ b/tools/perf/tests/shell/sched.sh
> @@ -0,0 +1,91 @@
> +#!/bin/bash
> +# perf sched tests
> +# SPDX-License-Identifier: GPL-2.0
> +
> +set -e
> +
> +if [ "$(id -u)" != 0 ]; then
> +  echo "[Skip] No root permission"
> +  exit 2
> +fi
> +
> +err=0
> +perfdata=$(mktemp /tmp/__perf_test_sched.perf.data.XXXXX)
> +PID1=0
> +PID2=0
> +
> +cleanup() {
> +  rm -f "${perfdata}"
> +  rm -f "${perfdata}".old
> +
> +  trap - EXIT TERM INT
> +}
> +
> +trap_cleanup() {
> +  echo "Unexpected signal in ${FUNCNAME[1]}"
> +  cleanup
> +  exit 1
> +}
> +trap trap_cleanup EXIT TERM INT
> +
> +start_noploops() {
> +  # Start two noploop workloads on CPU0 to trigger scheduling.
> +  taskset -c 0 perf test -w noploop 10 &
> +  PID1=$!
> +  taskset -c 0 perf test -w noploop 10 &
> +  PID2=$!
> +
> +  if ! grep -q 'Cpus_allowed_list:\s*0$' "/proc/$PID1/status"

Hi Ian,

Because taskset is also run in the background it's possible to grep the 
proc file before it's managed to re-pin itself. I saw some intermittent 
failures of the test because of this.

I think you'd need to run noploop in the background but taskset in the 
foreground and give it the pid of noploop to make sure it finishes 
before grepping.

Other than that the test seems ok:

Reviewed-by: James Clark <james.clark@linaro.org>

Thanks
James

> +  then
> +    echo "Sched [Error taskset did not work for the 1st noploop ($PID1)]"
> +    grep Cpus_allowed /proc/$PID1/status
> +    err=1
> +  fi
> +
> +  if ! grep -q 'Cpus_allowed_list:\s*0$' "/proc/$PID2/status"
> +  then
> +    echo "Sched [Error taskset did not work for the 2nd noploop ($PID2)]"
> +    grep Cpus_allowed /proc/$PID2/status
> +    err=1
> +  fi
> +}
> +
> +cleanup_noploops() {
> +  kill "$PID1" "$PID2"
> +}
> +
> +test_sched_latency() {
> +  echo "Sched latency"
> +
> +  start_noploops
> +
> +  perf sched record --no-inherit -o "${perfdata}" sleep 1
> +  if ! perf sched latency -i "${perfdata}" | grep -q perf-noploop
> +  then
> +    echo "Sched latency [Failed missing output]"
> +    err=1
> +  fi
> +
> +  cleanup_noploops
> +}
> +
> +test_sched_script() {
> +  echo "Sched script"
> +
> +  start_noploops
> +
> +  perf sched record --no-inherit -o "${perfdata}" sleep 1
> +  if ! perf sched script -i "${perfdata}" | grep -q perf-noploop
> +  then
> +    echo "Sched script [Failed missing output]"
> +    err=1
> +  fi
> +
> +  cleanup_noploops
> +}
> +
> +test_sched_latency
> +test_sched_script
> +
> +cleanup
> +exit $err