linux-kernel - Re: [PATCH] perf: test: Speed up running brstack test

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Message-ID: <Z2OzrfsiTaHagLt-@google.com>
Date: Wed, 18 Dec 2024 21:48:29 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: "Rob Herring (Arm)" <robh@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	James Clark <james.clark@...aro.org>,
	Anshuman Khandual <anshuman.khandual@....com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: test: Speed up running brstack test

On Fri, Dec 13, 2024 at 05:13:12PM -0600, Rob Herring (Arm) wrote:
> From: James Clark <james.clark@....com>
> 
> The brstack test runs quite slowly in software models. Part of the reason
> is "xargs -n1" is quite inefficient in replacing spaces with newlines.
> While that's not noticeable on normal machines, it is on software models.
> Use "tr -s ' ' '\n'" instead which can do the same transformation, but is
> much faster. For comparison on an M1 Macbook Pro:
> 
> $ time seq -s ' ' 10000 | xargs -n1 > /dev/null
> 
> real    0m2.729s
> user    0m2.009s
> sys     0m0.914s
> $ time seq -s ' ' 10000 | tr -s ' ' '\n' | grep '.' > /dev/null
> 
> real    0m0.002s
> user    0m0.001s
> sys     0m0.001s
> 
> The "grep '.'" is also needed to remove any remaining blank lines.
> 
> Signed-off-by: James Clark <james.clark@....com>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> [robh: Drop changing loop iterations on arm64. Squash blank line fix and redo commit msg]
> Signed-off-by: Rob Herring (Arm) <robh@...nel.org>

Reviewed-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung

> ---
> Originally part of this series[1], but I've dropped any Arm specifics, 
> and it stands on its own. No reason this needs to wait on Arm BRBE 
> support (which I'm working on now). I don't expect to have other changes 
> to this test related to BRBE anymore.
> 
> [1] https://lore.kernel.org/all/20240613061731.3109448-8-anshuman.khandual@arm.com/
> 
>  tools/perf/tests/shell/test_brstack.sh | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/tests/shell/test_brstack.sh b/tools/perf/tests/shell/test_brstack.sh
> index 5f14d0cb013f..e01df7581393 100755
> --- a/tools/perf/tests/shell/test_brstack.sh
> +++ b/tools/perf/tests/shell/test_brstack.sh
> @@ -30,7 +30,7 @@ test_user_branches() {
>  	echo "Testing user branch stack sampling"
>  
>  	perf record -o $TMPDIR/perf.data --branch-filter any,save_type,u -- ${TESTPROG} > /dev/null 2>&1
> -	perf script -i $TMPDIR/perf.data --fields brstacksym | xargs -n1 > $TMPDIR/perf.script
> +	perf script -i $TMPDIR/perf.data --fields brstacksym | tr -s ' ' '\n' > $TMPDIR/perf.script
>  
>  	# example of branch entries:
>  	# 	brstack_foo+0x14/brstack_bar+0x40/P/-/-/0/CALL
> @@ -59,7 +59,7 @@ test_filter() {
>  	echo "Testing branch stack filtering permutation ($test_filter_filter,$test_filter_expect)"
>  
>  	perf record -o $TMPDIR/perf.data --branch-filter $test_filter_filter,save_type,u -- ${TESTPROG} > /dev/null 2>&1
> -	perf script -i $TMPDIR/perf.data --fields brstack | xargs -n1 > $TMPDIR/perf.script
> +	perf script -i $TMPDIR/perf.data --fields brstack | tr -s ' ' '\n' | grep '.' > $TMPDIR/perf.script
>  
>  	# fail if we find any branch type that doesn't match any of the expected ones
>  	# also consider UNKNOWN branch types (-)
> -- 
> 2.45.2
>