perf evsel: Support perf_evsel__open(cpus > 1 && threads > 1)

And a test for it:

[acme@felicio linux]$ perf test
 1: vmlinux symtab matches kallsyms: Ok
 2: detect open syscall event: Ok
 3: detect open syscall event on all cpus: Ok
[acme@felicio linux]$

Translating C the test does:

1. generates different number of open syscalls on each CPU
   by using sched_setaffinity
2. Verifies that the expected number of events is generated
   on each CPU

It works as expected.

LKML-Reference: <new-submission>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

2 files changed, 159 insertions, 33 deletions

diff --git a/tools/perf/builtin-test.c b/tools/perf/builtin-test.c
index e12753f976a..ed5696198d3 100644
--- a/tools/perf/builtin-test.c
+++ b/tools/perf/builtin-test.c
@@ -234,6 +234,7 @@ out:
         return err;
 }
 
+#include "util/cpumap.h"
 #include "util/evsel.h"
 #include <sys/types.h>
 
@@ -321,6 +322,111 @@ out_thread_map_delete:
         return err;
 }
 
+#include <sched.h>
+
+static int test__open_syscall_event_on_all_cpus(void)
+{
+        int err = -1, fd, cpu;
+        struct thread_map *threads;
+        struct cpu_map *cpus;
+        struct perf_evsel *evsel;
+        struct perf_event_attr attr;
+        unsigned int nr_open_calls = 111, i;
+        cpu_set_t *cpu_set;
+        size_t cpu_set_size;
+        int id = trace_event__id("sys_enter_open");
+
+        if (id < 0) {
+                pr_debug("is debugfs mounted on /sys/kernel/debug?\n");
+                return -1;
+        }
+
+        threads = thread_map__new(-1, getpid());
+        if (threads == NULL) {
+                pr_debug("thread_map__new\n");
+                return -1;
+        }
+
+        cpus = cpu_map__new(NULL);
+        if (threads == NULL) {
+                pr_debug("thread_map__new\n");
+                return -1;
+        }
+
+        cpu_set = CPU_ALLOC(cpus->nr);
+
+        if (cpu_set == NULL)
+                goto out_thread_map_delete;
+
+        cpu_set_size = CPU_ALLOC_SIZE(cpus->nr);
+        CPU_ZERO_S(cpu_set_size, cpu_set);
+
+        memset(&attr, 0, sizeof(attr));
+        attr.type = PERF_TYPE_TRACEPOINT;
+        attr.config = id;
+        evsel = perf_evsel__new(&attr, 0);
+        if (evsel == NULL) {
+                pr_debug("perf_evsel__new\n");
+                goto out_cpu_free;
+        }
+
+        if (perf_evsel__open(evsel, cpus, threads) < 0) {
+                pr_debug("failed to open counter: %s, "
+                         "tweak /proc/sys/kernel/perf_event_paranoid?\n",
+                         strerror(errno));
+                goto out_evsel_delete;
+        }
+
+        for (cpu = 0; cpu < cpus->nr; ++cpu) {
+                unsigned int ncalls = nr_open_calls + cpu;
+
+                CPU_SET(cpu, cpu_set);
+                sched_setaffinity(0, cpu_set_size, cpu_set);
+                for (i = 0; i < ncalls; ++i) {
+                        fd = open("/etc/passwd", O_RDONLY);
+                        close(fd);
+                }
+                CPU_CLR(cpu, cpu_set);
+        }
+
+        /*
+         * Here we need to explicitely preallocate the counts, as if
+         * we use the auto allocation it will allocate just for 1 cpu,
+         * as we start by cpu 0.
+         */
+        if (perf_evsel__alloc_counts(evsel, cpus->nr) < 0) {
+                pr_debug("perf_evsel__alloc_counts(ncpus=%d)\n", cpus->nr);
+                goto out_close_fd;
+        }
+
+        for (cpu = 0; cpu < cpus->nr; ++cpu) {
+                unsigned int expected;
+
+                if (perf_evsel__read_on_cpu(evsel, cpu, 0) < 0) {
+                        pr_debug("perf_evsel__open_read_on_cpu\n");
+                        goto out_close_fd;
+                }
+
+                expected = nr_open_calls + cpu;
+                if (evsel->counts->cpu[cpu].val != expected) {
+                        pr_debug("perf_evsel__read_on_cpu: expected to intercept %d calls on cpu %d, got %Ld\n",
+                                 expected, cpu, evsel->counts->cpu[cpu].val);
+                        goto out_close_fd;
+                }
+        }
+
+        err = 0;
+out_close_fd:
+        perf_evsel__close_fd(evsel, 1, threads->nr);
+out_evsel_delete:
+        perf_evsel__delete(evsel);
+out_cpu_free:
+        CPU_FREE(cpu_set);
+out_thread_map_delete:
+        thread_map__delete(threads);
+        return err;
+}
+
 static struct test {
         const char *desc;
         int (*func)(void);
@@ -334,6 +440,10 @@ static struct test {
                 .func = test__open_syscall_event,
         },
         {
+                .desc = "detect open syscall event on all cpus",
+                .func = test__open_syscall_event_on_all_cpus,
+        },
+        {
                 .func = NULL,
         },
 };
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 1a5591d7a24..f5cfed60af9 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -127,59 +127,75 @@ int __perf_evsel__read(struct perf_evsel *evsel,
         return 0;
 }
 
-int perf_evsel__open_per_cpu(struct perf_evsel *evsel, struct cpu_map *cpus)
+static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
+                              struct thread_map *threads)
 {
-        int cpu;
+        int cpu, thread;
 
-        if (evsel->fd == NULL && perf_evsel__alloc_fd(evsel, cpus->nr, 1) < 0)
+        if (evsel->fd == NULL &&
+            perf_evsel__alloc_fd(evsel, cpus->nr, threads->nr) < 0)
                 return -1;
 
         for (cpu = 0; cpu < cpus->nr; cpu++) {
-                FD(evsel, cpu, 0) = sys_perf_event_open(&evsel->attr, -1,
-                                                        cpus->map[cpu], -1, 0);
-                if (FD(evsel, cpu, 0) < 0)
-                        goto out_close;
+                for (thread = 0; thread < threads->nr; thread++) {
+                        FD(evsel, cpu, thread) = sys_perf_event_open(&evsel->attr,
+                                                                     threads->map[thread],
+                                                                     cpus->map[cpu], -1, 0);
+                        if (FD(evsel, cpu, thread) < 0)
+                                goto out_close;
+                }
         }
 
         return 0;
 
 out_close:
-        while (--cpu >= 0) {
-                close(FD(evsel, cpu, 0));
-                FD(evsel, cpu, 0) = -1;
-        }
+        do {
+                while (--thread >= 0) {
+                        close(FD(evsel, cpu, thread));
+                        FD(evsel, cpu, thread) = -1;
+                }
+                thread = threads->nr;
+        } while (--cpu >= 0);
         return -1;
 }
 
-int perf_evsel__open_per_thread(struct perf_evsel *evsel, struct thread_map *threads)
+static struct {
+        struct cpu_map map;
+        int cpus[1];
+} empty_cpu_map = {
+        .map.nr = 1,
+        .cpus   = { -1, },
+};
+
+static struct {
+        struct thread_map map;
+        int threads[1];
+} empty_thread_map = {
+        .map.nr  = 1,
+        .threads = { -1, },
+};
+
+int perf_evsel__open(struct perf_evsel *evsel,
+                     struct cpu_map *cpus, struct thread_map *threads)
 {
-        int thread;
-
-        if (evsel->fd == NULL && perf_evsel__alloc_fd(evsel, 1, threads->nr))
-                return -1;
 
-        for (thread = 0; thread < threads->nr; thread++) {
-                FD(evsel, 0, thread) = sys_perf_event_open(&evsel->attr,
-                                                           threads->map[thread], -1, -1, 0);
-                if (FD(evsel, 0, thread) < 0)
-                        goto out_close;
+        if (cpus == NULL) {
+                /* Work around old compiler warnings about strict aliasing */
+                cpus = &empty_cpu_map.map;
         }
 
-        return 0;
+        if (threads == NULL)
+                threads = &empty_thread_map.map;
 
-out_close:
-        while (--thread >= 0) {
-                close(FD(evsel, 0, thread));
-                FD(evsel, 0, thread) = -1;
-        }
-        return -1;
+        return __perf_evsel__open(evsel, cpus, threads);
 }
 
-int perf_evsel__open(struct perf_evsel *evsel, 
-                     struct cpu_map *cpus, struct thread_map *threads)
+int perf_evsel__open_per_cpu(struct perf_evsel *evsel, struct cpu_map *cpus)
 {
-        if (threads == NULL)
-                return perf_evsel__open_per_cpu(evsel, cpus);
+        return __perf_evsel__open(evsel, cpus, &empty_thread_map.map);
+}
 
-        return perf_evsel__open_per_thread(evsel, threads);
+int perf_evsel__open_per_thread(struct perf_evsel *evsel, struct thread_map *threads)
+{
+        return __perf_evsel__open(evsel, &empty_cpu_map.map, threads);
 }