Re: [PATCH v3 04/13] perf tests: Add robust record retry helper and use subsecond workloads

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Jun 16, 2026 at 09:48:09AM -0700, Ian Rogers wrote:
> Introduce `perf_record_with_retry` and `perf_record_cleanup` in a shared
> library `tests/shell/lib/perf_record.sh` to prevent record test failures
> caused by transient recording or workload delays.
> 
> Update `record.sh`, `record_lbr.sh`, `pipe_test.sh`, `kvm.sh`, and
> `stat_all_pfm.sh` to use this robust record retry logic. These tests now
> start with very short durations (e.g. 0.01 seconds) and scale up if the
> initial recording failed to capture samples, significantly improving test
> execution speed on success while remaining resilient to slow systems.
> 
> Assisted-by: Antigravity:gemini-3.1-pro
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
[SNIP]
> @@ -60,22 +71,29 @@ test_kvm_stat() {
>  test_kvm_record_report() {
>  	echo "Testing perf kvm record/report"
>  
> -	echo "Recording kvm profile for pid ${qemu_pid}..."
> -	# Use --host to avoid needing guest symbols/mounts for this simple test
> -	# We just want to verify the command runs and produces data
> -	# We run in background and kill it because 'perf kvm record' appends options
> -	# after the command, which breaks 'sleep' (e.g. it gets '-e cycles').
> -	perf kvm --host record -p "${qemu_pid}" -o "${perfdata}" &
> -	rec_pid=$!
> -	sleep 1
> -	kill -INT "${rec_pid}"
> -	wait "${rec_pid}" || true
> +	local duration
> +	local success=false
> +	for duration in 1 2 4 8; do
> +		echo "Recording kvm profile for pid ${qemu_pid} (duration ${duration}s)..."
> +		rm -f "${perfdata}" "${perfdata}".old
> +
> +		perf kvm --host record -p "${qemu_pid}" -o "${perfdata}" &
> +		local rec_pid=$!
> +		sleep ${duration}
> +		kill -INT "${rec_pid}"
> +		wait "${rec_pid}" || true

Can this be just like below?

		perf kvm --host record -p "${qemu_pid}" -o "${perfdata}" sleep ${duration}

Thanks,
Namhyung

> +
> +		if [ -e "${perfdata}" ] && \
> +			perf kvm -i "${perfdata}" report --stdio 2>&1 | grep -q "Event count"; then
> +			success=true
> +			break
> +		fi
> +		echo "No samples or report failed, retrying..."
> +	done
>  
> -	echo "Reporting kvm profile..."
> -	# Check for some standard output from report
> -	if ! perf kvm -i "${perfdata}" report --stdio 2>&1 | grep -q "Event count"; then
> +	if [ "$success" = false ]; then
>  		echo "Failed to report kvm profile"
> -		perf kvm -i "${perfdata}" report --stdio 2>&1
> +		perf kvm -i "${perfdata}" report --stdio 2>&1 || true
>  		err=1
>  		return
>  	fi