Re: [PATCH v1 5/8] perf topology: Add core_wide

Arnaldo Carvalho de Melo
2022-08-31T14:40:39Z

Em Tue, Aug 30, 2022 at 09:48:43AM -0700, Ian Rogers escreveu:
> It is possible to optimize metrics when all SMT threads (CPUs) on a
> core are measuring events in system wide mode. For example, TMA
> metrics defines CORE_CLKS for Sandybrdige as:
>
> if SMT is disabled:
> CPU_CLK_UNHALTED.THREAD
> if SMT is enabled and recording on all SMT threads:
> CPU_CLK_UNHALTED.THREAD_ANY / 2
> if SMT is enabled and not recording on all SMT threads:
> (CPU_CLK_UNHALTED.THREAD/2)*
> (1+CPU_CLK_UNHALTED.ONE_THREAD_ACTIVE/CPU_CLK_UNHALTED.REF_XCLK )
>
> That is two more events are necessary when not gathering counts on all
> SMT threads. To distinguish all SMT threads on a core vs system wide
> (all CPUs) call the new property core wide. Add a core wide test that
> determines the property from user requested CPUs, the topology and
> system wide. System wide is required as other processes running on a
> SMT thread will change the counts.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
> tools/perf/util/cputopo.c | 46 +++++++++++++++++++++++++++++++++++++++
> tools/perf/util/cputopo.h | 3 +++
> tools/perf/util/smt.c | 14 ++++++++++++
> tools/perf/util/smt.h | 7 ++++++
> 4 files changed, 70 insertions(+)
>
> diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
> index 511002e52714..1a3ff6449158 100644
> --- a/tools/perf/util/cputopo.c
> +++ b/tools/perf/util/cputopo.c
> @@ -172,6 +172,52 @@ bool cpu_topology__smt_on(const struct cpu_topology *topology)
> return false;
> }
>
> +bool cpu_topology__core_wide(const struct cpu_topology *topology,
> + const char *user_requested_cpu_list)
> +{
> + struct perf_cpu_map *user_requested_cpus;
> +
> + /*
> + * If user_requested_cpu_list is empty then all CPUs are recorded and so
> + * core_wide is true.
> + */
> + if (!user_requested_cpu_list)
> + return true;
> +
> + user_requested_cpus = perf_cpu_map__new(user_requested_cpu_list);

Don't we need a NULL test here?

> + /* Check that every user requested CPU is the complete set of SMT threads on a core. */
> + for (u32 i = 0; i < topology->core_cpus_lists; i++) {
> + const char *core_cpu_list = topology->core_cpus_list[i];
> + struct perf_cpu_map *core_cpus = perf_cpu_map__new(core_cpu_list);

Here too, no?

> + struct perf_cpu cpu;
> + int idx;
> + bool has_first, first = true;
> +
> + perf_cpu_map__for_each_cpu(cpu, idx, core_cpus) {
> + if (first) {
> + has_first = perf_cpu_map__has(user_requested_cpus, cpu);
> + first = false;
> + } else {
> + /*
> + * If the first core CPU is user requested then
> + * all subsequent CPUs in the core must be user
> + * requested too. If the first CPU isn't user
> + * requested then none of the others must be
> + * too.
> + */
> + if (perf_cpu_map__has(user_requested_cpus, cpu) != has_first) {
> + perf_cpu_map__put(core_cpus);
> + perf_cpu_map__put(user_requested_cpus);
> + return false;
> + }
> + }
> + }
> + perf_cpu_map__put(core_cpus);
> + }
> + perf_cpu_map__put(user_requested_cpus);
> + return true;
> +}
> +
> static bool has_die_topology(void)
> {
> char filename[MAXPATHLEN];
> diff --git a/tools/perf/util/cputopo.h b/tools/perf/util/cputopo.h
> index 469db775a13c..969e5920a00e 100644
> --- a/tools/perf/util/cputopo.h
> +++ b/tools/perf/util/cputopo.h
> @@ -60,6 +60,9 @@ struct cpu_topology *cpu_topology__new(void);
> void cpu_topology__delete(struct cpu_topology *tp);
> /* Determine from the core list whether SMT was enabled. */
> bool cpu_topology__smt_on(const struct cpu_topology *topology);
> +/* Are the sets of SMT siblings all enabled or all disabled in user_requested_cpus. */
> +bool cpu_topology__core_wide(const struct cpu_topology *topology,
> + const char *user_requested_cpu_list);
>
> struct numa_topology *numa_topology__new(void);
> void numa_topology__delete(struct numa_topology *tp);
> diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
> index ce90c4ee4138..994e9e418227 100644
> --- a/tools/perf/util/smt.c
> +++ b/tools/perf/util/smt.c
> @@ -21,3 +21,17 @@ bool smt_on(const struct cpu_topology *topology)
> cached = true;
> return cached_result;
> }
> +
> +bool core_wide(bool system_wide, const char *user_requested_cpu_list,
> + const struct cpu_topology *topology)
> +{
> + /* If not everything running on a core is being recorded then we can't use core_wide. */
> + if (!system_wide)
> + return false;
> +
> + /* Cheap case that SMT is disabled and therefore we're inherently core_wide. */
> + if (!smt_on(topology))
> + return true;
> +
> + return cpu_topology__core_wide(topology, user_requested_cpu_list);
> +}
> diff --git a/tools/perf/util/smt.h b/tools/perf/util/smt.h
> index e26999c6b8d4..ae9095f2c38c 100644
> --- a/tools/perf/util/smt.h
> +++ b/tools/perf/util/smt.h
> @@ -7,4 +7,11 @@ struct cpu_topology;
> /* Returns true if SMT (aka hyperthreading) is enabled. */
> bool smt_on(const struct cpu_topology *topology);
>
> +/*
> + * Returns true when system wide and all SMT threads for a core are in the
> + * user_requested_cpus map.
> + */
> +bool core_wide(bool system_wide, const char *user_requested_cpu_list,
> + const struct cpu_topology *topology);
> +
> #endif /* __SMT_H */
> --
> 2.37.2.672.g94769d06f0-goog

--

- Arnaldo