[PATCH] libtracecmd: Optimize what cpus to check in tracecmd_iterate_events()

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

Currently, tracecmd_iterate_events() will look at all possible CPUs to
find the next event to print, even if the CPUs to look at are filtered.
Instead, create a list of all the CPUs to look at and iterate that, such
that only the CPUs that are needed are looked at instead of all of them,
including those that are filtered out.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 lib/trace-cmd/trace-input.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/lib/trace-cmd/trace-input.c b/lib/trace-cmd/trace-input.c
index ce4ecf43..2d12ac33 100644
--- a/lib/trace-cmd/trace-input.c
+++ b/lib/trace-cmd/trace-input.c
@@ -2813,9 +2813,12 @@ int tracecmd_iterate_events(struct tracecmd_input *handle,
 	struct tep_record *record;
 	unsigned long long *timestamps;
 	unsigned long long ts, last_timestamp = 0;
+	int *cpu_list;
+	int cpu_count = 0;
 	int next_cpu;
 	int cpu;
 	int ret = 0;
+	int i;
 
 	if (!callback && !handle->nr_followers) {
 		errno = EINVAL;
@@ -2826,17 +2829,28 @@ int tracecmd_iterate_events(struct tracecmd_input *handle,
 	if (!timestamps)
 		return -1;
 
+	cpu_list = calloc(handle->cpus, sizeof(*cpu_list));
+	if (!cpu_list) {
+		free(timestamps);
+		return -1;
+	}
+
 	for (cpu = 0; cpu < handle->cpus; cpu++) {
 		if (cpus && !CPU_ISSET_S(cpu, cpu_size, cpus))
 			continue;
+		cpu_list[cpu_count++] = cpu;
+	}
 
+	for (i = 0; i < cpu_count; i++) {
+		cpu = cpu_list[i];
 		record = tracecmd_peek_data(handle, cpu);
 		timestamps[cpu] = record ? record->ts : -1ULL;
 	}
 
 	do {
 		next_cpu = -1;
-		for (cpu = 0; cpu < handle->cpus; cpu++) {
+		for (i = 0; i < cpu_count; i++) {
+			cpu = cpu_list[i];
 			ts = timestamps[cpu];
 			if (ts == -1ULL)
 				continue;
@@ -2869,6 +2883,7 @@ int tracecmd_iterate_events(struct tracecmd_input *handle,
 	} while (next_cpu >= 0 && ret == 0);
 
 	free(timestamps);
+	free(cpu_list);
 
 	return ret;
 }
-- 
2.43.0