Merge pull request ocaml#13299 from stedolan/remove-memprof-global-param

Simplify memprof internals by removing "global" param

runtime/caml/memprof.h

@@ -64,35 +64,23 @@ extern void caml_memprof_update_suspended(_Bool);
  * point to minor heaps (the `SCANNING_ONLY_YOUNG_VALUES` flag).
  *
  * If `weak` is false then only scan strong roots. If `weak`
- * is true then also scan weak roots.
- *
- * If `global` is false then only scan roots for `state`. If `global`
- * is true then also scan roots shared between all domains. */
+ * is true then also scan weak roots. */
 
 extern void caml_memprof_scan_roots(scanning_action f,
                                     scanning_action_flags fflags,
                                     void* fdata,
                                     caml_domain_state *state,
-                                    _Bool weak,
-                                    _Bool global);
+                                    _Bool weak);
 
 /* Update memprof data structures for the domain `state`, to reflect
- * survival and promotion, after a minor GC is completed.
- *
- * If `global` is false then only update structures for `state`. If
- * `global` is true then also update structures shared between all
- * domains. */
+ * survival and promotion, after a minor GC is completed. */
 
-extern void caml_memprof_after_minor_gc(caml_domain_state *state, _Bool global);
+extern void caml_memprof_after_minor_gc(caml_domain_state *state);
 
 /* Update memprof data structures for the domain `state`, to reflect
- * survival, after a minor GC is completed.
- *
- * If `global` is false then only update structures for `state`. If
- * `global` is true then also update structures shared between all
- * domains. */
+ * survival, after a minor GC is completed. */
 
-extern void caml_memprof_after_major_gc(caml_domain_state *state, _Bool global);
+extern void caml_memprof_after_major_gc(caml_domain_state *state);
 
 /* Freshly computes state->memprof_young_trigger. *Does not* set the
  * young limit. */

runtime/major_gc.c

@@ -1408,7 +1408,7 @@ static void stw_cycle_all_domains(
    * mysteriously put all domains back into mark/sweep.
    */
   CAML_EV_BEGIN(EV_MAJOR_MEMPROF_CLEAN);
-  caml_memprof_after_major_gc(domain, domain == participating[0]);
+  caml_memprof_after_major_gc(domain);
   CAML_EV_END(EV_MAJOR_MEMPROF_CLEAN);
 
   CAML_EV_BEGIN(EV_MAJOR_GC_CYCLE_DOMAINS);
@@ -1487,7 +1487,7 @@ static void stw_cycle_all_domains(
 
   CAML_EV_BEGIN(EV_MAJOR_MEMPROF_ROOTS);
   caml_memprof_scan_roots(caml_darken, darken_scanning_flags, domain,
-                          domain, false, participating[0] == Caml_state);
+                          domain, false);
   CAML_EV_END(EV_MAJOR_MEMPROF_ROOTS);
 
   if (domain->mark_stack->count == 0 &&

runtime/memprof.c

@@ -626,9 +626,12 @@ struct memprof_orphan_table_s {
 /* List of orphaned entry tables not yet adopted by any domain. */
 static memprof_orphan_table_t orphans = NULL;
 
-/* lock controlling access to `orphans` variable */
+/* lock controlling access to `orphans` and writes to `orphans_present` */
 static caml_plat_mutex orphans_lock = CAML_PLAT_MUTEX_INITIALIZER;
 
+/* Flag indicating non-NULL orphans. Only modified when holding orphans_lock. */
+static atomic_uintnat orphans_present;
+
 /**** Initializing and clearing entries tables ****/
 
 static void entries_init(entries_t es, size_t min_capacity, value config)
@@ -965,6 +968,7 @@ static void orphans_abandon(memprof_domain_t domain)
   caml_plat_lock_blocking(&orphans_lock);
   ot->next = orphans;
   orphans = domain->orphans;
+  atomic_store_release(&orphans_present, 1);
   caml_plat_unlock(&orphans_lock);
   domain->orphans = NULL;
 }
@@ -973,15 +977,21 @@ static void orphans_abandon(memprof_domain_t domain)
 
 static void orphans_adopt(memprof_domain_t domain)
 {
+  if (!atomic_load_acquire(&orphans_present))
+    return; /* No orphans to adopt */
+
   /* Find the end of the domain's orphans list */
   memprof_orphan_table_t *p = &domain->orphans;
   while(*p) {
     p = &(*p)->next;
   }
 
   caml_plat_lock_blocking(&orphans_lock);
-  *p = orphans;
-  orphans = NULL;
+  if (orphans) {
+    *p = orphans;
+    orphans = NULL;
+    atomic_store_release(&orphans_present, 0);
+  }
   caml_plat_unlock(&orphans_lock);
 }
 
@@ -1463,15 +1473,13 @@ void caml_memprof_scan_roots(scanning_action f,
                              scanning_action_flags fflags,
                              void* fdata,
                              caml_domain_state *state,
-                             bool weak,
-                             bool global)
+                             bool weak)
 {
   memprof_domain_t domain = state->memprof;
   CAMLassert(domain);
-  if (global) {
-    /* Adopt all global orphans into this domain. */
-    orphans_adopt(domain);
-  }
+
+  /* Adopt all global orphans into this domain. */
+  orphans_adopt(domain);
 
   bool young = (fflags & SCANNING_ONLY_YOUNG_VALUES);
   struct scan_closure closure = {f, fflags, fdata, weak};
@@ -1515,17 +1523,15 @@ static void entries_update_after_minor_gc(entries_t entries,
 }
 
 /* Update all memprof structures for a given domain, at the end of a
- * minor GC. If `global` is set, also ensure shared structures are
- * updated (we do this by adopting orphans into this domain). */
+ * minor GC. */
 
-void caml_memprof_after_minor_gc(caml_domain_state *state, bool global)
+void caml_memprof_after_minor_gc(caml_domain_state *state)
 {
   memprof_domain_t domain = state->memprof;
   CAMLassert(domain);
-  if (global) {
-    /* Adopt all global orphans into this domain. */
-    orphans_adopt(domain);
-  }
+
+  /* Adopt all global orphans into this domain. */
+  orphans_adopt(domain);
 
   domain_apply_actions(domain, true, entry_update_after_minor_gc,
                        NULL, entries_update_after_minor_gc);
@@ -1558,17 +1564,16 @@ static bool entry_update_after_major_gc(entry_t e, void *data)
  * is no "entries_update_after_major_gc" function. */
 
 /* Update all memprof structures for a given domain, at the end of a
- * major GC. If `global` is set, also update shared structures (we do
- * this by adopting orphans into this domain). */
+ * major GC. */
 
-void caml_memprof_after_major_gc(caml_domain_state *state, bool global)
+void caml_memprof_after_major_gc(caml_domain_state *state)
 {
   memprof_domain_t domain = state->memprof;
   CAMLassert(domain);
-  if (global) {
-    /* Adopt all global orphans into this domain. */
-    orphans_adopt(domain);
-  }
+
+  /* Adopt all global orphans into this domain. */
+  orphans_adopt(domain);
+
   domain_apply_actions(domain, false, entry_update_after_major_gc,
                        NULL, NULL);
   orphans_update_pending(domain);

runtime/minor_gc.c

@@ -596,7 +596,7 @@ void caml_empty_minor_heap_promote(caml_domain_state* domain,
 
   CAML_EV_BEGIN(EV_MINOR_MEMPROF_ROOTS);
   caml_memprof_scan_roots(&oldify_one, oldify_scanning_flags, &st,
-                          domain, false, participating[0] == domain);
+                          domain, false);
   CAML_EV_END(EV_MINOR_MEMPROF_ROOTS);
 
   CAML_EV_BEGIN(EV_MINOR_REMEMBERED_SET_PROMOTE);
@@ -633,7 +633,7 @@ void caml_empty_minor_heap_promote(caml_domain_state* domain,
   CAML_EV_END(EV_MINOR_LOCAL_ROOTS);
 
   CAML_EV_BEGIN(EV_MINOR_MEMPROF_CLEAN);
-  caml_memprof_after_minor_gc(domain, participating[0] == domain);
+  caml_memprof_after_minor_gc(domain);
   CAML_EV_END(EV_MINOR_MEMPROF_CLEAN);
 
   domain->young_ptr = domain->young_end;

runtime/shared_heap.c

@@ -1223,7 +1223,7 @@ void caml_compact_heap(caml_domain_state* domain_state,
 
   /* Memprof roots and "weak" pointers to tracked blocks */
   caml_memprof_scan_roots(&compact_update_value, 0, NULL,
-                          Caml_state, true, participants[0] == Caml_state);
+                          Caml_state, true);
 
   /* Next, one domain does the global roots */
   if (participants[0] == Caml_state) {