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-rw-r--r--tools/perf/util/Build1
-rw-r--r--tools/perf/util/affinity.c73
-rw-r--r--tools/perf/util/affinity.h17
-rw-r--r--tools/perf/util/python-ext-sources1
4 files changed, 92 insertions, 0 deletions
diff --git a/tools/perf/util/Build b/tools/perf/util/Build
index aab05e2c01a5..07da6c790b63 100644
--- a/tools/perf/util/Build
+++ b/tools/perf/util/Build
@@ -77,6 +77,7 @@ perf-y += sort.o
perf-y += hist.o
perf-y += util.o
perf-y += cpumap.o
+perf-y += affinity.o
perf-y += cputopo.o
perf-y += cgroup.o
perf-y += target.o
diff --git a/tools/perf/util/affinity.c b/tools/perf/util/affinity.c
new file mode 100644
index 000000000000..a5e31f826828
--- /dev/null
+++ b/tools/perf/util/affinity.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Manage affinity to optimize IPIs inside the kernel perf API. */
+#define _GNU_SOURCE 1
+#include <sched.h>
+#include <stdlib.h>
+#include <linux/bitmap.h>
+#include <linux/zalloc.h>
+#include "perf.h"
+#include "cpumap.h"
+#include "affinity.h"
+
+static int get_cpu_set_size(void)
+{
+ int sz = cpu__max_cpu() + 8 - 1;
+ /*
+ * sched_getaffinity doesn't like masks smaller than the kernel.
+ * Hopefully that's big enough.
+ */
+ if (sz < 4096)
+ sz = 4096;
+ return sz / 8;
+}
+
+int affinity__setup(struct affinity *a)
+{
+ int cpu_set_size = get_cpu_set_size();
+
+ a->orig_cpus = bitmap_alloc(cpu_set_size * 8);
+ if (!a->orig_cpus)
+ return -1;
+ sched_getaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
+ a->sched_cpus = bitmap_alloc(cpu_set_size * 8);
+ if (!a->sched_cpus) {
+ zfree(&a->orig_cpus);
+ return -1;
+ }
+ bitmap_zero((unsigned long *)a->sched_cpus, cpu_set_size);
+ a->changed = false;
+ return 0;
+}
+
+/*
+ * perf_event_open does an IPI internally to the target CPU.
+ * It is more efficient to change perf's affinity to the target
+ * CPU and then set up all events on that CPU, so we amortize
+ * CPU communication.
+ */
+void affinity__set(struct affinity *a, int cpu)
+{
+ int cpu_set_size = get_cpu_set_size();
+
+ if (cpu == -1)
+ return;
+ a->changed = true;
+ set_bit(cpu, a->sched_cpus);
+ /*
+ * We ignore errors because affinity is just an optimization.
+ * This could happen for example with isolated CPUs or cpusets.
+ * In this case the IPIs inside the kernel's perf API still work.
+ */
+ sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->sched_cpus);
+ clear_bit(cpu, a->sched_cpus);
+}
+
+void affinity__cleanup(struct affinity *a)
+{
+ int cpu_set_size = get_cpu_set_size();
+
+ if (a->changed)
+ sched_setaffinity(0, cpu_set_size, (cpu_set_t *)a->orig_cpus);
+ zfree(&a->sched_cpus);
+ zfree(&a->orig_cpus);
+}
diff --git a/tools/perf/util/affinity.h b/tools/perf/util/affinity.h
new file mode 100644
index 000000000000..0ad6a18ef20c
--- /dev/null
+++ b/tools/perf/util/affinity.h
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef PERF_AFFINITY_H
+#define PERF_AFFINITY_H 1
+
+#include <stdbool.h>
+
+struct affinity {
+ unsigned long *orig_cpus;
+ unsigned long *sched_cpus;
+ bool changed;
+};
+
+void affinity__cleanup(struct affinity *a);
+void affinity__set(struct affinity *a, int cpu);
+int affinity__setup(struct affinity *a);
+
+#endif // PERF_AFFINITY_H
diff --git a/tools/perf/util/python-ext-sources b/tools/perf/util/python-ext-sources
index 9af183860fbd..e7279ea6043a 100644
--- a/tools/perf/util/python-ext-sources
+++ b/tools/perf/util/python-ext-sources
@@ -33,3 +33,4 @@ util/trace-event.c
util/string.c
util/symbol_fprintf.c
util/units.c
+util/affinity.c