[RFC PATCH v1 10/37] perf evlist: add multithreading helper

[Riccardo Mancini]

This patch adds the function evlist__for_each_evsel_cpu, which executes
the given function on each evsel, for each cpu.

If perf_singlethreaded is unset, this function will use a workqueue to
execute the function.

This helper function will be used in the following patches.

Signed-off-by: Riccardo Mancini <rickyman7@xxxxxxxxx>
---
 tools/perf/util/evlist.c | 117 +++++++++++++++++++++++++++++++++++++++
 tools/perf/util/evlist.h |  14 +++++
 2 files changed, 131 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 3d55d9a53b9f4875..f9fdbd85a163ee97 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -27,6 +27,8 @@
 #include "util/perf_api_probe.h"
 #include "util/evsel_fprintf.h"
 #include "util/evlist-hybrid.h"
+#include "util/util.h"
+#include "util/workqueue/workqueue.h"
 #include <signal.h>
 #include <unistd.h>
 #include <sched.h>
@@ -41,6 +43,7 @@
 #include <sys/prctl.h>
 
 #include <linux/bitops.h>
+#include <linux/kernel.h>
 #include <linux/hash.h>
 #include <linux/log2.h>
 #include <linux/err.h>
@@ -369,6 +372,120 @@ static int evlist__is_enabled(struct evlist *evlist)
 	return false;
 }
 
+struct evlist_work {
+	struct work_struct work;
+	struct evlist *evlist;
+	int cpu;
+	evsel__cpu_func func;
+	void *args;
+	int ret;
+};
+
+static void evlist__for_each_evsel_cpu_thread_func(struct work_struct *_work)
+{
+	struct evlist_work *work = container_of(_work, struct evlist_work, work);
+	int cpu_idx, ret, err = 0;
+	struct evsel *pos;
+
+	work->ret = 0;
+	evlist__for_each_entry(work->evlist, pos) {
+		cpu_idx = evsel__find_cpu(pos, work->cpu);
+		if (cpu_idx < 0)
+			continue;
+		ret = work->func(work->evlist, pos, cpu_idx, work->args);
+		if (ret) {
+			work->ret = ret;
+			if (err < 0)		// error
+				return;
+		}
+	}
+}
+
+static int evlist__for_each_evsel_cpu_multithreaded(struct evlist *evlist,
+					evsel__cpu_func func, void *args)
+{
+	int i, cpu, ret;
+	struct evlist_work *works;
+	char errbuf[WORKQUEUE_STRERR_BUFSIZE];
+
+	works = calloc(perf_cpu_map__nr(evlist->core.all_cpus), sizeof(*works));
+	perf_cpu_map__for_each_cpu(cpu, i, evlist->core.all_cpus) {
+		init_work(&works[i].work);
+		works[i].evlist = evlist;
+		works[i].work.func = evlist__for_each_evsel_cpu_thread_func;
+		works[i].cpu = cpu;
+		works[i].func = func;
+		works[i].args = args;
+		works[i].ret = 0;
+
+		ret = schedule_work_on(cpu, &works[i].work);
+		if (ret) {
+			workqueue_strerror(global_wq, ret, errbuf, sizeof(errbuf));
+			pr_debug("schedule_work: %s\n", errbuf);
+			break;
+		}
+	}
+
+	ret = flush_scheduled_work();
+	if (ret) {
+		workqueue_strerror(global_wq, ret, errbuf, sizeof(errbuf));
+		pr_debug("flush_scheduled_work: %s\n", errbuf);
+		goto out;
+	}
+
+	perf_cpu_map__for_each_cpu(cpu, i, evlist->core.all_cpus) {
+		if (works[i].ret) {
+			ret = works[i].ret;
+			if (works[i].ret < 0)		// error
+				goto out;
+		}
+	}
+out:
+	free(works);
+
+	return ret;
+}
+
+static int evlist__for_each_evsel_cpu_singlethreaded(struct evlist *evlist,
+					evsel__cpu_func func, void *args)
+{
+	int ret, err = 0, i, cpu, cpu_idx;
+	struct affinity affinity;
+	struct evsel *pos;
+
+	if (affinity__setup(&affinity) < 0)
+		return -1;
+
+	evlist__for_each_cpu(evlist, i, cpu) {
+		affinity__set(&affinity, cpu);
+
+		evlist__for_each_entry(evlist, pos) {
+			cpu_idx = evsel__find_cpu(pos, cpu);
+			if (cpu_idx < 0)
+				continue;
+			ret = func(evlist, pos, cpu_idx, args);
+			if (ret) {
+				err = ret;
+				if (err < 0)		// error
+					goto out;
+			}
+		}
+	}
+
+out:
+	affinity__cleanup(&affinity);
+	return err;
+}
+
+int evlist__for_each_evsel_cpu(struct evlist *evlist, evsel__cpu_func func, void *args)
+{
+	if (perf_singlethreaded)
+		return evlist__for_each_evsel_cpu_singlethreaded(evlist, func, args);
+	else
+		return evlist__for_each_evsel_cpu_multithreaded(evlist, func, args);
+
+}
+
 static void __evlist__disable(struct evlist *evlist, char *evsel_name)
 {
 	struct evsel *pos;
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index fde893170c7ba6d2..5f24a45d4e3cf30a 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -363,4 +363,18 @@ struct evsel *evlist__find_evsel(struct evlist *evlist, int idx);
 
 int evlist__scnprintf_evsels(struct evlist *evlist, size_t size, char *bf);
 void evlist__check_mem_load_aux(struct evlist *evlist);
+
+/**
+ * evsel__cpu_func - function to run on each evsel for each cpu
+ * @evlist: the parent evlist
+ * @evsel: the processed evsel
+ * @cpu: index of the cpu in evsel->core.cpus
+ * @args: additional custom arguments
+ *
+ * Returns:
+ * A negative value is considered as an error.
+ * A positive value will be propagated to evlist__for_each_evsel_cpu.
+ */
+typedef int (*evsel__cpu_func)(struct evlist *evlist, struct evsel *evsel, int cpu, void *args);
+int evlist__for_each_evsel_cpu(struct evlist *evlist, evsel__cpu_func func, void *args);
 #endif /* __PERF_EVLIST_H */
-- 
2.31.1