Re: libperf: CPU map question

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Feb 14, 2022 at 06:54:38PM +0200, Tzvetomir Stoyanov wrote:
> Hello,
> I'm trying to use libperf as an interface to perf from an application,
> but I face some difficulties.  I cannot understand how perf_cpu_map_
> APIs should be used. My use case is:
>  I want to iterate over the CPUs from the map. I'm using
> perf_evsel__cpus() API to get the map and perf_cpu_map__for_each_cpu()
> macros to iterate over the map. However, using that logic I get a
> struct perf_cpu for each CPU from the map. That structure seems to be
> private and I cannot access the actual .cpu id. Am I missing something
> ?
> Will be glad for any help and clarification.

yea it's a bug ;-) there was a change recently that wrapped cpu
in struct perf_cpu to distinguish it from cpu indexes

  6d18804b963b perf cpumap: Give CPUs their own type

not sure there's workaround for that.. but I think change below should fix it

Ian, would this be ok? we need to add some test for this

jirka


---
diff --git a/tools/lib/perf/include/internal/cpumap.h b/tools/lib/perf/include/internal/cpumap.h
index 581f9ffb4237..1973a18c096b 100644
--- a/tools/lib/perf/include/internal/cpumap.h
+++ b/tools/lib/perf/include/internal/cpumap.h
@@ -3,11 +3,7 @@
 #define __LIBPERF_INTERNAL_CPUMAP_H
 
 #include <linux/refcount.h>
-
-/** A wrapper around a CPU to avoid confusion with the perf_cpu_map's map's indices. */
-struct perf_cpu {
-	int cpu;
-};
+#include <perf/cpumap.h>
 
 /**
  * A sized, reference counted, sorted array of integers representing CPU
diff --git a/tools/lib/perf/include/perf/cpumap.h b/tools/lib/perf/include/perf/cpumap.h
index 15b8faafd615..4a2edbdb5e2b 100644
--- a/tools/lib/perf/include/perf/cpumap.h
+++ b/tools/lib/perf/include/perf/cpumap.h
@@ -7,6 +7,11 @@
 #include <stdio.h>
 #include <stdbool.h>
 
+/** A wrapper around a CPU to avoid confusion with the perf_cpu_map's map's indices. */
+struct perf_cpu {
+	int cpu;
+};
+
 LIBPERF_API struct perf_cpu_map *perf_cpu_map__dummy_new(void);
 LIBPERF_API struct perf_cpu_map *perf_cpu_map__default_new(void);
 LIBPERF_API struct perf_cpu_map *perf_cpu_map__new(const char *cpu_list);