Re: [PATCH] perf test: Add test for branch stack sampling

[Ian Rogers]

On Wed, Jun 15, 2022 at 6:09 AM German Gomez <german.gomez@xxxxxxx> wrote:
>
> Add a self test for branch stack sampling, to check that we get the
> expected branch types, and filters behave as expected.
>
> Suggested-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> Signed-off-by: German Gomez <german.gomez@xxxxxxx>

Love tests, thanks! There are already shell tests that compile C code
but they do it by having the C code within the shell test, for
example:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/tests/shell/pipe_test.sh?h=perf/core#n14
Having it this way I thinks means the tests can run properly when
installed, as we don't install non-sh files:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/perf/Makefile.perf?h=perf/core#n1016

Thanks,
Ian

> ---
>  tools/perf/tests/shell/lib/brstack/main.h | 16 +++++
>  tools/perf/tests/shell/lib/brstack/test.c | 24 +++++++
>  tools/perf/tests/shell/test_brstack.sh    | 86 +++++++++++++++++++++++
>  3 files changed, 126 insertions(+)
>  create mode 100644 tools/perf/tests/shell/lib/brstack/main.h
>  create mode 100644 tools/perf/tests/shell/lib/brstack/test.c
>  create mode 100755 tools/perf/tests/shell/test_brstack.sh
>
> diff --git a/tools/perf/tests/shell/lib/brstack/main.h b/tools/perf/tests/shell/lib/brstack/main.h
> new file mode 100644
> index 000000000..94d2665ec
> --- /dev/null
> +++ b/tools/perf/tests/shell/lib/brstack/main.h
> @@ -0,0 +1,16 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#define BENCH_RUNS 99999
> +
> +void bench(void);
> +
> +int main(void)
> +{
> +       int cnt = 0;
> +
> +       while (1) {
> +               if ((cnt++) > BENCH_RUNS)
> +                       break;
> +               bench();                /* call */
> +       }                               /* branch (uncond) */
> +       return 0;
> +}
> diff --git a/tools/perf/tests/shell/lib/brstack/test.c b/tools/perf/tests/shell/lib/brstack/test.c
> new file mode 100644
> index 000000000..8a2308901
> --- /dev/null
> +++ b/tools/perf/tests/shell/lib/brstack/test.c
> @@ -0,0 +1,24 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include "main.h"
> +
> +int cnt;
> +
> +void bar(void)
> +{
> +}                              /* return */
> +
> +void foo(void)
> +{
> +       bar();                  /* call */
> +}                              /* return */
> +
> +void bench(void)
> +{
> +       void (*foo_ind)(void) = foo;
> +
> +       if ((cnt++) % 3)        /* branch (cond) */
> +               foo();          /* call */
> +
> +       bar();                  /* call */
> +       foo_ind();              /* call (ind) */
> +}
> diff --git a/tools/perf/tests/shell/test_brstack.sh b/tools/perf/tests/shell/test_brstack.sh
> new file mode 100755
> index 000000000..2b1a1b20a
> --- /dev/null
> +++ b/tools/perf/tests/shell/test_brstack.sh
> @@ -0,0 +1,86 @@
> +#!/bin/sh
> +# Check branch stack sampling
> +
> +# SPDX-License-Identifier: GPL-2.0
> +# German Gomez <german.gomez@xxxxxxx>, 2022
> +
> +set -e
> +
> +# we need a C compiler to build the test programs
> +# so bail if none is found
> +if ! [ -x "$(command -v cc)" ]; then
> +       echo "failed: no compiler, install gcc"
> +       exit 2
> +fi
> +
> +# skip the test if the hardware doesn't support branch stack sampling
> +perf record -b -o- -- true > /dev/null || exit 2
> +
> +TMPDIR=$(mktemp -d /tmp/__perf_test.program.XXXXX)
> +
> +cleanup() {
> +       rm -rf $TMPDIR
> +}
> +
> +trap cleanup exit term int
> +
> +test_user_branches() {
> +       echo
> +       echo "Testing user branch stack sampling"
> +       echo
> +
> +       cc -fno-inline -g "$(dirname $0)/lib/brstack/test.c" -o $TMPDIR/a.out
> +
> +       perf record -o $TMPDIR/perf.data -q --branch-filter any,save_type,u -- $TMPDIR/a.out
> +       perf script -i $TMPDIR/perf.data --fields brstacksym | xargs -n1 > $TMPDIR/perf.script
> +
> +       # example of branch entries:
> +       #       foo+0x14/bar+0x40/P/-/-/0/CALL
> +
> +       set -x
> +       egrep -m1 "^bench\+[^ ]*/foo\+[^ ]*/IND_CALL$"  $TMPDIR/perf.script
> +       egrep -m1 "^foo\+[^ ]*/bar\+[^ ]*/CALL$"        $TMPDIR/perf.script
> +       egrep -m1 "^bench\+[^ ]*/foo\+[^ ]*/CALL$"      $TMPDIR/perf.script
> +       egrep -m1 "^bench\+[^ ]*/bar\+[^ ]*/CALL$"      $TMPDIR/perf.script
> +       egrep -m1 "^bar\+[^ ]*/foo\+[^ ]*/RET$"         $TMPDIR/perf.script
> +       egrep -m1 "^foo\+[^ ]*/bench\+[^ ]*/RET$"       $TMPDIR/perf.script
> +       egrep -m1 "^bench\+[^ ]*/bench\+[^ ]*/COND$"    $TMPDIR/perf.script
> +       egrep -m1 "^main\+[^ ]*/main\+[^ ]*/UNCOND$"    $TMPDIR/perf.script
> +       set +x
> +
> +       # some branch types are still not being tested:
> +       # IND COND_CALL COND_RET SYSCALL SYSRET IRQ SERROR NO_TX
> +}
> +
> +test_filter() {
> +       local filter=$1
> +       local expect=$2
> +
> +       echo
> +       echo "Testing branch stack filtering permutation ($filter,$expect)"
> +       echo
> +
> +       cc -fno-inline -g "$(dirname $0)/lib/brstack/test.c" -o $TMPDIR/a.out
> +
> +       perf record -o $TMPDIR/perf.data -q --branch-filter $filter,save_type,u -- $TMPDIR/a.out
> +       perf script -i $TMPDIR/perf.data --fields brstack | xargs -n1 > $TMPDIR/perf.script
> +
> +       # fail if we find any branch type that doesn't match any of the expected ones
> +       # also consider UNKNOWN branch types (-)
> +       if egrep -vm1 "^[^ ]*/($expect|-|( *))$" $TMPDIR/perf.script; then
> +               return 1
> +       fi
> +}
> +
> +test_user_branches
> +
> +# first argument <arg0> is the argument passed to "--branch-stack <arg0>,save_type,u"
> +# second argument are the expected branch types for the given filter
> +test_filter "any_call" "CALL|IND_CALL|COND_CALL|SYSCALL|IRQ|FAULT_DATA|FAULT_INST"
> +test_filter "call"     "CALL|SYSCALL"
> +test_filter "cond"     "COND"
> +test_filter "any_ret"  "RET|COND_RET|SYSRET|ERET"
> +
> +test_filter "call,cond"                "CALL|SYSCALL|COND"
> +test_filter "any_call,cond"            "CALL|IND_CALL|COND_CALL|IRQ|FAULT_DATA|FAULT_INST|SYSCALL|COND"
> +test_filter "cond,any_call,any_ret"    "COND|CALL|IND_CALL|COND_CALL|SYSCALL|IRQ|FAULT_DATA|FAULT_INST|RET|COND_RET|SYSRET|ERET"
> --
> 2.25.1
>