linux-kernel - Re: [PATCH v7 11/13] perf tools: Improve IBS error handling

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Message-ID: <Yj44ICldLB6h0Mcu@kernel.org>
Date:   Fri, 25 Mar 2022 18:46:08 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        kim.phillips@....com, acme@...hat.com, jolsa@...hat.com,
        songliubraving@...com, rafael@...nel.org, ravi.bangoria@....com,
        sandipan.das@....com
Subject: Re: [PATCH v7 11/13] perf tools: Improve IBS error handling

Em Tue, Mar 22, 2022 at 03:15:15PM -0700, Stephane Eranian escreveu:
> From: Kim Phillips <kim.phillips@....com>
> 
> improve the error message returned on failed perf_event_open() on AMD when
> using IBS.
> 
> Output of executing 'perf record -e ibs_op// true' BEFORE this patch:
> 
> The sys_perf_event_open() syscall returned with 22 (Invalid argument)for event (ibs_op//u).
> /bin/dmesg | grep -i perf may provide additional information.
> 
> Output after:
> 
> AMD IBS cannot exclude kernel events.  Try running at a higher privilege level.

So the error message don't match up the BEFORE part, that didn't have a
"u" at the end, and with this patch in:

  $ git log --oneline -1
  ca585f91ce13df4c (HEAD -> perf/core) perf evsel: Improve AMD IBS (Instruction-Based Sampling) error handling messages
  # perf -v
  perf version 5.17.gca585f91ce13
  #
  
On a:

  # grep -m1 "model name" /proc/cpuinfo
  model name	: AMD Ryzen 9 5950X 16-Core Processor
  #

If I try:

  # perf record -e ibs_op//u true
  Error:
  Invalid event (ibs_op//u) in per-thread mode, enable system wide with '-a'.
  # 

So now if I try:

  # perf record -a -e ibs_op//u true
  Error:
  AMD IBS can't exclude kernel events.  Try running at a higher privilege level.
  #

So the problem is with the patch description, I'm fixing it.

> Output of executing 'sudo perf record -e ibs_op// true' BEFORE this patch:
> 
> Error:
> The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (ibs_op//).
> /bin/dmesg | grep -i perf may provide additional information.
> 
> Output after:
> 
> Error:
> AMD IBS may only be available in system-wide/per-cpu mode.  Try using -a, or -C and workload affinity

But this one is never reached:

[root@...e ~]# perf record -e ibs_op// true
Error:
Invalid event (ibs_op//) in per-thread mode, enable system wide with '-a'

> +                             if (!evsel->core.system_wide)
> +                                     return scnprintf(msg, size,
> +     "AMD IBS may only be available in system-wide/per-cpu mode.  Try using -a, or -C and workload affinity");


I'm applying this to make progress, the message now provides more clues.

- Arnaldo

 
> Signed-off-by: Kim Phillips <kim.phillips@....com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: Ian Rogers <irogers@...gle.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Jiri Olsa <jolsa@...hat.com>
> Cc: Joao Martins <joao.m.martins@...cle.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Michael Petlan <mpetlan@...hat.com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Robert Richter <robert.richter@....com>
> Cc: Stephane Eranian <eranian@...gle.com>
> ---
>  tools/perf/util/evsel.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 14b0e7ffa2c7..e8ff7a4bd490 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2847,9 +2847,23 @@ static bool find_process(const char *name)
>  	return ret ? false : true;
>  }
>  
> +static bool is_amd(const char *arch, const char *cpuid)
> +{
> +	return arch && !strcmp("x86", arch) && cpuid && strstarts(cpuid, "AuthenticAMD");
> +}
> +
> +static bool is_amd_ibs(struct evsel *evsel)
> +{
> +	return evsel->core.attr.precise_ip
> +	    || (evsel->pmu_name && !strncmp(evsel->pmu_name, "ibs", 3));
> +}
> +
>  int evsel__open_strerror(struct evsel *evsel, struct target *target,
>  			 int err, char *msg, size_t size)
>  {
> +	struct perf_env *env = evsel__env(evsel);
> +	const char *arch = perf_env__arch(env);
> +	const char *cpuid = perf_env__cpuid(env);
>  	char sbuf[STRERR_BUFSIZE];
>  	int printed = 0, enforced = 0;
>  
> @@ -2949,6 +2963,17 @@ int evsel__open_strerror(struct evsel *evsel, struct target *target,
>  			return scnprintf(msg, size,
>  	"Invalid event (%s) in per-thread mode, enable system wide with '-a'.",
>  					evsel__name(evsel));
> +		if (is_amd(arch, cpuid)) {
> +			if (is_amd_ibs(evsel)) {
> +				if (evsel->core.attr.exclude_kernel)
> +					return scnprintf(msg, size,
> +	"AMD IBS can't exclude kernel events.  Try running at a higher privilege level.");
> +				if (!evsel->core.system_wide)
> +					return scnprintf(msg, size,
> +	"AMD IBS may only be available in system-wide/per-cpu mode.  Try using -a, or -C and workload affinity");
> +			}
> +		}
> +
>  		break;
>  	case ENODATA:
>  		return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "
> -- 
> 2.35.1.894.gb6a874cedc-goog

-- 

- Arnaldo