Expose counts for each GC reason in GC.stat

This information is currently only available through debug counters
which makes it unpractical to use in production.

However this information is very useful to optimize GC in applications.

gc.c

@@ -798,7 +798,21 @@ typedef struct rb_objspace {
         double invoke_time;
 
         size_t minor_gc_count;
+        size_t minor_gc_newobj_count;
+        size_t minor_gc_malloc_count;
+        size_t minor_gc_method_count;
+        size_t minor_gc_capi_count;
+        size_t minor_gc_stress_count;
+
         size_t major_gc_count;
+        size_t major_gc_nofree_count;
+        size_t major_gc_oldgen_count;
+        size_t major_gc_shady_count;
+        size_t major_gc_force_count;
+#if RGENGC_ESTIMATE_OLDMALLOC
+        size_t major_gc_oldmalloc_count;
+#endif
+
         size_t compact_count;
         size_t read_barrier_faults;
 #if RGENGC_PROFILE > 0
@@ -9551,6 +9565,20 @@ gc_start(rb_objspace_t *objspace, unsigned int reason)
 #endif
 
     objspace->profile.count++;
+    if (reason & GPR_FLAG_MAJOR_BY_NOFREE) objspace->profile.major_gc_nofree_count++;
+    if (reason & GPR_FLAG_MAJOR_BY_OLDGEN) objspace->profile.major_gc_oldgen_count++;
+    if (reason & GPR_FLAG_MAJOR_BY_SHADY) objspace->profile.major_gc_shady_count++;
+    if (reason & GPR_FLAG_MAJOR_BY_FORCE) objspace->profile.major_gc_force_count++;
+#if RGENGC_ESTIMATE_OLDMALLOC
+    if (reason & GPR_FLAG_MAJOR_BY_OLDMALLOC) objspace->profile.major_gc_oldmalloc_count++;
+#endif
+
+    if (reason & GPR_FLAG_NEWOBJ) objspace->profile.minor_gc_newobj_count++;
+    if (reason & GPR_FLAG_MALLOC) objspace->profile.minor_gc_malloc_count++;
+    if (reason & GPR_FLAG_METHOD) objspace->profile.minor_gc_method_count++;
+    if (reason & GPR_FLAG_CAPI) objspace->profile.minor_gc_capi_count++;
+    if (reason & GPR_FLAG_STRESS) objspace->profile.minor_gc_stress_count++;
+
     objspace->profile.latest_gc_info = reason;
     objspace->profile.total_allocated_objects_at_gc_start = objspace->total_allocated_objects;
     objspace->profile.heap_used_at_gc_start = heap_allocated_pages;
@@ -11206,6 +11234,19 @@ enum gc_stat_sym {
     gc_stat_sym_malloc_increase_bytes_limit,
     gc_stat_sym_minor_gc_count,
     gc_stat_sym_major_gc_count,
+    gc_stat_sym_major_gc_nofree_count,
+    gc_stat_sym_major_gc_oldgen_count,
+    gc_stat_sym_major_gc_shady_count,
+    gc_stat_sym_major_gc_force_count,
+#if RGENGC_ESTIMATE_OLDMALLOC
+    gc_stat_sym_major_gc_oldmalloc_count,
+#endif
+    gc_stat_sym_minor_gc_newobj_count,
+    gc_stat_sym_minor_gc_malloc_count,
+    gc_stat_sym_minor_gc_method_count,
+    gc_stat_sym_minor_gc_capi_count,
+    gc_stat_sym_minor_gc_stress_count,
+
     gc_stat_sym_compact_count,
     gc_stat_sym_read_barrier_faults,
     gc_stat_sym_total_moved_objects,
@@ -11253,8 +11294,23 @@ setup_gc_stat_symbols(void)
         S(total_freed_objects);
         S(malloc_increase_bytes);
         S(malloc_increase_bytes_limit);
-        S(minor_gc_count);
+
         S(major_gc_count);
+        S(major_gc_nofree_count);
+        S(major_gc_oldgen_count);
+        S(major_gc_shady_count);
+        S(major_gc_force_count);
+#if RGENGC_ESTIMATE_OLDMALLOC
+        S(major_gc_oldmalloc_count);
+#endif
+
+        S(minor_gc_count);
+        S(minor_gc_newobj_count);
+        S(minor_gc_malloc_count);
+        S(minor_gc_method_count);
+        S(minor_gc_capi_count);
+        S(minor_gc_stress_count);
+
         S(compact_count);
         S(read_barrier_faults);
         S(total_moved_objects);
@@ -11322,8 +11378,25 @@ gc_stat_internal(VALUE hash_or_sym)
     SET(total_freed_objects, objspace->profile.total_freed_objects);
     SET(malloc_increase_bytes, malloc_increase);
     SET(malloc_increase_bytes_limit, malloc_limit);
-    SET(minor_gc_count, objspace->profile.minor_gc_count);
+
+    SET(major_gc_count, objspace->profile.major_gc_count);
     SET(major_gc_count, objspace->profile.major_gc_count);
+    SET(major_gc_nofree_count, objspace->profile.major_gc_nofree_count);
+    SET(major_gc_oldgen_count, objspace->profile.major_gc_oldgen_count);
+    SET(major_gc_shady_count, objspace->profile.major_gc_shady_count);
+    SET(major_gc_force_count, objspace->profile.major_gc_force_count);
+#if RGENGC_ESTIMATE_OLDMALLOC
+    SET(major_gc_oldmalloc_count, objspace->profile.major_gc_oldmalloc_count);
+#endif
+
+    SET(minor_gc_count, objspace->profile.minor_gc_count);
+    SET(minor_gc_count, objspace->profile.minor_gc_count);
+    SET(minor_gc_newobj_count, objspace->profile.minor_gc_newobj_count);
+    SET(minor_gc_malloc_count, objspace->profile.minor_gc_malloc_count);
+    SET(minor_gc_method_count, objspace->profile.minor_gc_method_count);
+    SET(minor_gc_capi_count, objspace->profile.minor_gc_capi_count);
+    SET(minor_gc_stress_count, objspace->profile.minor_gc_stress_count);
+
     SET(compact_count, objspace->profile.compact_count);
     SET(read_barrier_faults, objspace->profile.read_barrier_faults);
     SET(total_moved_objects, objspace->rcompactor.total_moved);