linux-kernel - Re: [PATCH] perf test arm64: Test unwinding using fame-pointer (fp) mode

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Date:   Tue, 15 Mar 2022 14:32:56 +0000
From:   German Gomez <german.gomez@....com>
To:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Cc:     Jiri Olsa <jolsa@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        James Clark <james.clark@....com>, acme@...nel.org
Subject: Re: [PATCH] perf test arm64: Test unwinding using fame-pointer (fp)
 mode


On 01/03/2022 13:34, German Gomez wrote:
> Add a shell script to check that the call-graphs generated using frame
> pointers (--call-graph fp) are complete and not missing leaf functions:
>
> [...]
>
> +cat << EOF > $TEST_PROGRAM_SOURCE
> +int a = 0;
> +void leaf(void) {
> +  for (;;)
> +    a += a;
> +}
> +void parent(void) {
> +  leaf();
> +}
> +int main(void) {
> +  parent();
> +  return 0;
> +}
> +EOF
> +
> +echo " + Compiling test program ($TEST_PROGRAM)..."
> +CFLAGS="-O0 -fno-inline -fno-omit-frame-pointer"

This fails when the test program is compiled with gcc-7, due to missing -g flag.

I will re-spin with this fixed.

> +cc $CFLAGS $TEST_PROGRAM_SOURCE -o $TEST_PROGRAM || exit 1
> +
> +# Add a 1 second delay to skip samples that are not in the leaf() function
> +perf record -o $PERF_DATA --call-graph fp -e cycles//u -D 1000 -- $TEST_PROGRAM 2> /dev/null &
> +PID=$!
> +echo " + Recording (PID=$PID)..."
> +sleep 2
> +echo " + Stopping perf-record..."
> +kill $PID
> +wait $PID
> +
> +# example perf-script output:
> +#
> +# program 
> +# 	728 leaf
> +# 	753 parent
> +# 	76c main
> +# ...
> +
> +perf script -i $PERF_DATA -F comm,ip,sym | head -n4
> +perf script -i $PERF_DATA -F comm,ip,sym | head -n4 |
> +	awk '{ if ($2 != "") sym[i++] = $2 } END { if (sym[0] != "leaf" ||
> +						       sym[1] != "parent" ||
> +						       sym[2] != "main") exit 1 }'