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In-Reply-To: <1673601740-122788-2-git-send-email-renyu.zj@linux.alibaba.com>
From:   Ian Rogers <irogers@google.com>
Date:   Sat, 14 Jan 2023 14:15:40 -0800
Message-ID: <CAP-5=fWnOGD7CHYeq0Uino4eHte2WP5Pxz9t4YOtvgxrq-_muA@mail.gmail.com>
Subject: Re: [PATCH v7 1/9] perf pmu: Add #slots literal support for arm64
To:     Jing Zhang <renyu.zj@linux.alibaba.com>
Cc:     John Garry <john.g.garry@oracle.com>,
        Xing Zhengjun <zhengjun.xing@linux.intel.com>,
        Will Deacon <will@kernel.org>,
        James Clark <james.clark@arm.com>,
        Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        linux-arm-kernel@lists.infradead.org,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Andrew Kilroy <andrew.kilroy@arm.com>,
        Shuai Xue <xueshuai@linux.alibaba.com>,
        Zhuo Song <zhuo.song@linux.alibaba.com>
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On Fri, Jan 13, 2023 at 1:22 AM Jing Zhang <renyu.zj@linux.alibaba.com> wrote:
>
> The slots in each architecture may be different, so add #slots literal
> to obtain the slots of different architectures, and the #slots can be
> applied in the metric. Currently, The #slots just support for arm64,
> and other architectures will return NAN.
>
> On arm64, the value of slots is from the register PMMIR_EL1.SLOT, which
> I can read in /sys/bus/event_source/device/armv8_pmuv3_*/caps/slots.
> PMMIR_EL1.SLOT might read as zero if the PMU version is lower than
> ID_AA64DFR0_EL1_PMUVer_V3P4 or the STALL_SLOT event is not implemented.
>
> Signed-off-by: Jing Zhang <renyu.zj@linux.alibaba.com>
> ---
>  tools/perf/arch/arm64/util/pmu.c | 34 ++++++++++++++++++++++++++++++++--
>  tools/perf/util/expr.c           |  5 +++++
>  tools/perf/util/pmu.c            |  6 ++++++
>  tools/perf/util/pmu.h            |  1 +
>  4 files changed, 44 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/arch/arm64/util/pmu.c b/tools/perf/arch/arm64/util/pmu.c
> index 477e513..5f8667b 100644
> --- a/tools/perf/arch/arm64/util/pmu.c
> +++ b/tools/perf/arch/arm64/util/pmu.c
> @@ -3,8 +3,9 @@
>  #include <internal/cpumap.h>
>  #include "../../../util/cpumap.h"
>  #include "../../../util/pmu.h"
> +#include <api/fs/fs.h>
>
> -const struct pmu_events_table *pmu_events_table__find(void)
> +static struct perf_pmu *pmu_core__find_same(void)

I'm not sure "find_same" is the best name here. I suspect it should be
"find_core_pmu" which would agree with is_arm_pmu_core. Unfortunately
"core" has become an overloaded term sometimes used interchangeably
with CPU, hyperthread or SMT thread, it was a model name for Intel and
it is used to distinguish a set of SMT threads running together from a
single one. Anyway, for consistency I think perf_pmu__find_core_pmu is
the most appropriate name (or pmu__find_core_pmu, I'm not sure why we
get the extra perf_ prefix sometimes, in general that indicates the
functionality is in libperf).

Aside from that, lgtm. Thanks,
Ian

>  {
>         struct perf_pmu *pmu = NULL;
>
> @@ -19,8 +20,37 @@ const struct pmu_events_table *pmu_events_table__find(void)
>                 if (pmu->cpus->nr != cpu__max_cpu().cpu)
>                         return NULL;
>
> -               return perf_pmu__find_table(pmu);
> +               return pmu;
>         }
>
>         return NULL;
>  }
> +
> +const struct pmu_events_table *pmu_events_table__find(void)
> +{
> +       struct perf_pmu *pmu = pmu_core__find_same();
> +
> +       if (pmu)
> +               return perf_pmu__find_table(pmu);
> +
> +       return NULL;
> +}
> +
> +double perf_pmu__cpu_slots_per_cycle(void)
> +{
> +       char path[PATH_MAX];
> +       unsigned long long slots = 0;
> +       struct perf_pmu *pmu = pmu_core__find_same();
> +
> +       if (pmu) {
> +               scnprintf(path, PATH_MAX,
> +                       EVENT_SOURCE_DEVICE_PATH "%s/caps/slots", pmu->name);
> +               /*
> +                * The value of slots is not greater than 32 bits, but sysfs__read_int
> +                * can't read value with 0x prefix, so use sysfs__read_ull instead.
> +                */
> +               sysfs__read_ull(path, &slots);
> +       }
> +
> +       return (double)slots;
> +}
> diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
> index 00dcde3..9d3076a 100644
> --- a/tools/perf/util/expr.c
> +++ b/tools/perf/util/expr.c
> @@ -19,6 +19,7 @@
>  #include <linux/zalloc.h>
>  #include <ctype.h>
>  #include <math.h>
> +#include "pmu.h"
>
>  #ifdef PARSER_DEBUG
>  extern int expr_debug;
> @@ -448,6 +449,10 @@ double expr__get_literal(const char *literal, const struct expr_scanner_ctx *ctx
>                 result = topology->core_cpus_lists;
>                 goto out;
>         }
> +       if (!strcmp("#slots", literal)) {
> +               result = perf_pmu__cpu_slots_per_cycle() ?: NAN;
> +               goto out;
> +       }
>
>         pr_err("Unrecognized literal '%s'", literal);
>  out:
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 2bdeb89..cbb4fbf 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -19,6 +19,7 @@
>  #include <regex.h>
>  #include <perf/cpumap.h>
>  #include <fnmatch.h>
> +#include <math.h>
>  #include "debug.h"
>  #include "evsel.h"
>  #include "pmu.h"
> @@ -1993,3 +1994,8 @@ int perf_pmu__cpus_match(struct perf_pmu *pmu, struct perf_cpu_map *cpus,
>         *ucpus_ptr = unmatched_cpus;
>         return 0;
>  }
> +
> +double __weak perf_pmu__cpu_slots_per_cycle(void)
> +{
> +       return NAN;
> +}
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index 69ca000..fd414ba 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -259,4 +259,5 @@ int perf_pmu__cpus_match(struct perf_pmu *pmu, struct perf_cpu_map *cpus,
>
>  char *pmu_find_real_name(const char *name);
>  char *pmu_find_alias_name(const char *name);
> +double perf_pmu__cpu_slots_per_cycle(void);
>  #endif /* __PMU_H */
> --
> 1.8.3.1
>