AP_HAL_Linux: Perf: make lttng use internal fields

Instead of creating a new object Perf_Lttng copying the necessaries
fields, just make a tighter integration with the internal perf counters
and re-use the same fields.

libraries/AP_HAL_Linux/Perf.cpp

@@ -86,9 +86,7 @@ void Perf::begin(Util::perf_counter_t pc)
 
     perf.start = now_nsec();
 
-#ifdef HAVE_LTTNG_UST
-    perf.lttng.begin();
-#endif
+    perf.lttng.begin(perf.name);
 }
 
 void Perf::end(Util::perf_counter_t pc)
@@ -137,9 +135,7 @@ void Perf::end(Util::perf_counter_t pc)
     perf.m2 += (delta_intvl * (elapsed - perf.mean));
     perf.start = 0;
 
-#ifdef HAVE_LTTNG_UST
-    perf.lttng.end();
-#endif
+    perf.lttng.end(perf.name);
 }
 
 void Perf::count(Util::perf_counter_t pc)
@@ -161,10 +157,7 @@ void Perf::count(Util::perf_counter_t pc)
     _update_count++;
     perf.count++;
 
-#ifdef HAVE_LTTNG_UST
-    perf.lttng.count();
-#endif
-
+    perf.lttng.count(perf.name, perf.count);
 }
 
 Util::perf_counter_t Perf::add(Util::perf_counter_type type, const char *name)

libraries/AP_HAL_Linux/Perf.h

@@ -37,17 +37,12 @@ public:
     Perf_Counter(perf_counter_type type_, const char *name_)
         : name{name_}
         , type{type_}
-#ifdef HAVE_LTTNG_UST
-        , lttng{name_}
-#endif
         , least{ULONG_MAX}
     {
     }
 
     const char *name;
-#ifdef HAVE_LTTNG_UST
     Perf_Lttng lttng;
-#endif
 
     perf_counter_type type;
 

libraries/AP_HAL_Linux/Perf_Lttng.cpp

@@ -19,32 +19,35 @@
 
 #include <string.h>
 
-#include <AP_HAL/AP_HAL.h>
-
 #include "AP_HAL_Linux.h"
 #include "Perf_Lttng_TracePoints.h"
 #include "Perf_Lttng.h"
 
 using namespace Linux;
 
-Perf_Lttng::Perf_Lttng(const char *name)
+void Perf_Lttng::begin(const char *name)
 {
-    strncpy(_name, name, MAX_TRACEPOINT_NAME_LEN);
+    tracepoint(ardupilot, begin, name);
 }
 
-void Perf_Lttng::begin()
+void Perf_Lttng::end(const char *name)
 {
-    tracepoint(ardupilot, begin, _name);
+    tracepoint(ardupilot, end, name);
 }
 
-void Perf_Lttng::end()
+void Perf_Lttng::count(const char *name, uint64_t val)
 {
-    tracepoint(ardupilot, end, _name);
+    tracepoint(ardupilot, count, name, val);
 }
 
-void Perf_Lttng::count()
-{
-    tracepoint(ardupilot, count, _name, ++_count);
-}
+#else
+
+#include "Perf_Lttng.h"
+
+using namespace Linux;
+
+void Perf_Lttng::begin(const char *name) { }
+void Perf_Lttng::end(const char *name) { }
+void Perf_Lttng::count(const char *name, uint64_t val) { }
 
 #endif

libraries/AP_HAL_Linux/Perf_Lttng.h

@@ -14,23 +14,17 @@
  */
 #pragma once
 
-#include <AP_HAL/Util.h>
+#include <inttypes.h>
 
 #include "AP_HAL_Linux.h"
 
-#define MAX_TRACEPOINT_NAME_LEN 128
-
 namespace Linux {
 
 class Perf_Lttng {
 public:
-    Perf_Lttng(const char *name);
-    void begin();
-    void end();
-    void count();
-private:
-    char _name[MAX_TRACEPOINT_NAME_LEN];
-    uint64_t _count;
+    void begin(const char *name);
+    void end(const char *name);
+    void count(const char *name, uint64_t val);
 };
 
 }

libraries/AP_HAL_Linux/Perf_Lttng_TracePoints.h

@@ -28,7 +28,7 @@ TRACEPOINT_EVENT(
     ardupilot,
     begin,
     TP_ARGS(
-        char*, name_arg
+        const char*, name_arg
     ),
     TP_FIELDS(
         ctf_string(name_field, name_arg)
@@ -39,7 +39,7 @@ TRACEPOINT_EVENT(
     ardupilot,
     end,
     TP_ARGS(
-        char*, name_arg
+        const char*, name_arg
     ),
     TP_FIELDS(
         ctf_string(name_field, name_arg)
@@ -50,7 +50,7 @@ TRACEPOINT_EVENT(
     ardupilot,
     count,
     TP_ARGS(
-        char*, name_arg,
+        const char*, name_arg,
         int, count_arg
     ),
     TP_FIELDS(