Messages in this thread | | | From | Ian Rogers <> | Date | Wed, 31 Aug 2022 08:58:49 -0700 | Subject | Re: [PATCH v1 5/8] perf topology: Add core_wide |
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On Wed, Aug 31, 2022 at 7:40 AM Arnaldo Carvalho de Melo <acme@kernel.org> wrote: > > 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?
No, NULL is a valid perf_cpu_map, one with no values in it. For example, see here: https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/lib/perf/cpumap.c?h=perf/core#n266 So there's no way to tell an error (ENOMEM) from an empty map. My suggestion is a rewrite of perf_cpu_map, I'd like to do this in a new "libperf2" which has a more permissive than GPL license like libbpf. That is out-of-scope here.
Thanks, Ian
> > + /* 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
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