linux-kernel - Re: [PATCH 1/2 v2] perf test: Fix perf test 114 perf record test subtest precise

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Message-ID: <30865b2c-c58d-4974-9a88-dc13b8ad1195@linaro.org>
Date: Wed, 29 Jan 2025 09:57:42 +0000
From: James Clark <james.clark@...aro.org>
To: Thomas Richter <tmricht@...ux.ibm.com>, namhyung@...nel.org
Cc: agordeev@...ux.ibm.com, gor@...ux.ibm.com, sumanthk@...ux.ibm.com,
 hca@...ux.ibm.com, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, acme@...nel.org
Subject: Re: [PATCH 1/2 v2] perf test: Fix perf test 114 perf record test
 subtest precise_max for s390


Is this a v2 of "[PATCH] perf test: Fix perf test 114 perf record test 
for s390"? Or maybe the v2 is a typo?

On 29/01/2025 7:11 am, Thomas Richter wrote:
> On s390 the event instructions can not be used for recording.
> This event is only supported by perf stat.
> 
> Change the event instruction to cycles for subtest test_precise_max
> as suggested by James Clark.
> 
> Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
> Suggested-by: James Clark <james.clark@...aro.org>
> ---
>   tools/perf/tests/shell/record.sh | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
> index 0fc7a909ae9b..957ee10aff44 100755
> --- a/tools/perf/tests/shell/record.sh
> +++ b/tools/perf/tests/shell/record.sh
> @@ -287,9 +287,9 @@ test_precise_max() {
>       return
>     fi
>     # On AMD, cycles and instructions events are treated differently
> -  if ! perf record -o "${perfdata}" -e "instructions:P" true 2> /dev/null
> +  if ! perf record -o "${perfdata}" -e "cycles:P" true 2> /dev/null

I'm not sure if this is the right fix. Doesn't this make the test test 
cycles:P twice now?

I think the fix is to first test if cycles can be sampled, then test 
cycles:P. Then test if instructions can be sampled, then test 
instructions:P.

At the moment it checks the events with perf stat, and it checks them 
both at the same time. Obviously that doesn't work if an event works for 
perf stat but not perf record. And checking them both at the same time 
doesn't allow for one existing and not the other.

>     then
> -    echo "precise_max attribute [Failed instructions:P event]"
> +    echo "precise_max attribute [Failed cycles:P event]"
>       err=1
>       return
>     fi