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

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Wed, Jun 17, 2026 at 03:37:06PM -0700, Namhyung Kim wrote:
> 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}

Right, looks equivalent and simpler,

I was making notes to address the flakiness that is making me use the
end summary of entries that fail (great feature) to run them in
isolation to check if they work that way, which most do :-\

- Arnaldo

> 
> 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