linux-kernel - Re: [PATCH linux-next] perf stat: Regression perf stat -T cpi fails on s390 z/VM guest systems

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Message-ID: <CAP-5=fUNQL_qr_MY7VaJVVfC4gsxu0Gg4pAGPNfFY7onJVgGRQ@mail.gmail.com>
Date: Thu, 13 Nov 2025 10:32:38 -0800
From: Ian Rogers <irogers@...gle.com>
To: Thomas Richter <tmricht@...ux.ibm.com>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, acme@...nel.org, namhyung@...nel.org, 
	agordeev@...ux.ibm.com, gor@...ux.ibm.com, sumanthk@...ux.ibm.com, 
	hca@...ux.ibm.com, japo@...ux.ibm.com
Subject: Re: [PATCH linux-next] perf stat: Regression perf stat -T cpi fails
 on s390 z/VM guest systems

On Thu, Nov 13, 2025 at 12:29 AM Thomas Richter <tmricht@...ux.ibm.com> wrote:
>
> On s390 z/VM systems (linux guest on s390 LPAR) this happens:
>
>  # perf test 96 97
>  96: perf all metricgroups test        : FAILED!
>  97: perf all metrics test             : FAILED!
>
> This test works on the linux repo:
>  # perf test 95 96
>  95: perf all metricgroups test        : Ok
>  96: perf all metrics test             : Ok
>
> On both systems the command
>  # ./perf list --raw-dump metric
>  cpi est_cpi finite_cpi l1mp l2p l3p l4lp l4rp memp prbstate scpl1m \
>         tlb_miss tlb_percent transaction
> shows the same list of available metrics.
>
> On z/VM the CPU Measurement facilities do not exist:
>
>  # ll  /sys/devices/cpum_cf/events
>  ls: cannot access '/sys/devices/cpum_cf/events': No such file or directory
>  #
>
> The json files for s390 define the metric 'cpi' in
> arch/s390/cf_z16/transaction.json:
>
>   {
>     "BriefDescription": "Cycles per Instruction",
>     "MetricName": "cpi",
>     "MetricExpr": "CPU_CYCLES / INSTRUCTIONS \
>                                 if has_event(INSTRUCTIONS) else 0"
>   },
>
> The macro has_event(INSTRUCTIONS) now refers to a legacy event which
> always exists. It is always true even when the hardware does not
> support this event. Change the has_event(xxx) to check for a hardware
> event not available, for example CPU_CYCLES.
>
> Fixes: 0012e0fa221b ("perf jevents: Add legacy-hardware and legacy-cache json")
> Suggested by: Ian Rogers <irogers@...gle.com>
> Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>

This fix is equivalent to:
https://lore.kernel.org/lkml/20251112162439.1553368-1-irogers@google.com/
I'm easy about which one is picked up, the commit message here has more detail.

Reviewed-by: Ian Rogers <irogers@...gle.com>

Thanks,
Ian

> ---
>  tools/perf/pmu-events/arch/s390/cf_z16/transaction.json | 8 ++++----
>  tools/perf/pmu-events/arch/s390/cf_z17/transaction.json | 8 ++++----
>  2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/tools/perf/pmu-events/arch/s390/cf_z16/transaction.json b/tools/perf/pmu-events/arch/s390/cf_z16/transaction.json
> index 3ab1d3a6638c..26c550621d6a 100644
> --- a/tools/perf/pmu-events/arch/s390/cf_z16/transaction.json
> +++ b/tools/perf/pmu-events/arch/s390/cf_z16/transaction.json
> @@ -7,17 +7,17 @@
>    {
>      "BriefDescription": "Cycles per Instruction",
>      "MetricName": "cpi",
> -    "MetricExpr": "CPU_CYCLES / INSTRUCTIONS if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "CPU_CYCLES / INSTRUCTIONS if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Problem State Instruction Ratio",
>      "MetricName": "prbstate",
> -    "MetricExpr": "(PROBLEM_STATE_INSTRUCTIONS / INSTRUCTIONS) * 100 if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "(PROBLEM_STATE_INSTRUCTIONS / INSTRUCTIONS) * 100 if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Level One Miss per 100 Instructions",
>      "MetricName": "l1mp",
> -    "MetricExpr": "((L1I_DIR_WRITES + L1D_DIR_WRITES) / INSTRUCTIONS) * 100 if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "((L1I_DIR_WRITES + L1D_DIR_WRITES) / INSTRUCTIONS) * 100 if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Percentage sourced from Level 2 cache",
> @@ -52,7 +52,7 @@
>    {
>      "BriefDescription": "Estimated Instruction Complexity CPI infinite Level 1",
>      "MetricName": "est_cpi",
> -    "MetricExpr": "(CPU_CYCLES / INSTRUCTIONS) - (L1C_TLB2_MISSES / INSTRUCTIONS) if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "(CPU_CYCLES / INSTRUCTIONS) - (L1C_TLB2_MISSES / INSTRUCTIONS) if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Estimated Sourcing Cycles per Level 1 Miss",
> diff --git a/tools/perf/pmu-events/arch/s390/cf_z17/transaction.json b/tools/perf/pmu-events/arch/s390/cf_z17/transaction.json
> index 74df533c8b6f..4d296e0c8934 100644
> --- a/tools/perf/pmu-events/arch/s390/cf_z17/transaction.json
> +++ b/tools/perf/pmu-events/arch/s390/cf_z17/transaction.json
> @@ -7,17 +7,17 @@
>    {
>      "BriefDescription": "Cycles per Instruction",
>      "MetricName": "cpi",
> -    "MetricExpr": "CPU_CYCLES / INSTRUCTIONS if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "CPU_CYCLES / INSTRUCTIONS if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Problem State Instruction Ratio",
>      "MetricName": "prbstate",
> -    "MetricExpr": "(PROBLEM_STATE_INSTRUCTIONS / INSTRUCTIONS) * 100 if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "(PROBLEM_STATE_INSTRUCTIONS / INSTRUCTIONS) * 100 if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Level One Miss per 100 Instructions",
>      "MetricName": "l1mp",
> -    "MetricExpr": "((L1I_DIR_WRITES + L1D_DIR_WRITES) / INSTRUCTIONS) * 100 if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "((L1I_DIR_WRITES + L1D_DIR_WRITES) / INSTRUCTIONS) * 100 if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Percentage sourced from Level 2 cache",
> @@ -52,7 +52,7 @@
>    {
>      "BriefDescription": "Estimated Instruction Complexity CPI infinite Level 1",
>      "MetricName": "est_cpi",
> -    "MetricExpr": "(CPU_CYCLES / INSTRUCTIONS) - (L1C_TLB2_MISSES / INSTRUCTIONS) if has_event(INSTRUCTIONS) else 0"
> +    "MetricExpr": "(CPU_CYCLES / INSTRUCTIONS) - (L1C_TLB2_MISSES / INSTRUCTIONS) if has_event(CPU_CYCLES) else 0"
>    },
>    {
>      "BriefDescription": "Estimated Sourcing Cycles per Level 1 Miss",
> --
> 2.51.1
>