perf topology: Add core_wide

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>
Cc: Ahmad Yasin <ahmad.yasin@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Caleb Biggers <caleb.biggers@intel.com>
Cc: Florian Fischer <florian.fischer@muhq.space>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Garry <john.garry@huawei.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kshipra Bopardikar <kshipra.bopardikar@intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Miaoqian Lin <linmq006@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Perry Taylor <perry.taylor@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220831174926.579643-5-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
index 511002e..1a3ff64 100644 (file)
--- 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);
+       /* 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);
+               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 469db77..969e592 100644 (file)
--- 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 ce90c4e..994e9e4 100644 (file)
--- 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 e26999c..ae9095f 100644 (file)
--- 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 */