Allocating weak references, genericmemory and buffers into a non-moving space

Author: Luis Eduardo de Souza Amorim

src/gc-mmtk.c

@@ -240,6 +240,7 @@ JL_DLLEXPORT void jl_gc_collect(jl_gc_collection_t collection) {
         return;
     }
     mmtk_handle_user_collection_request(ptls, collection);
+    // print_fragmentation();
 }
 
 
@@ -330,6 +331,7 @@ JL_DLLEXPORT void jl_gc_prepare_to_collect(void)
     SetLastError(last_error);
 #endif
     errno = last_errno;
+    // print_fragmentation();
 }
 
 JL_DLLEXPORT unsigned char jl_gc_pin_object(void* obj) {
@@ -1064,9 +1066,8 @@ JL_DLLEXPORT size_t jl_gc_genericmemory_how(void *arg) JL_NOTSAFEPOINT
 
 JL_DLLEXPORT jl_weakref_t *jl_gc_new_weakref_th(jl_ptls_t ptls, jl_value_t *value)
 {
-    jl_weakref_t *wr = (jl_weakref_t*)jl_gc_alloc(ptls, sizeof(void*), jl_weakref_type);
+    jl_weakref_t *wr = (jl_weakref_t*)jl_gc_alloc_nonmoving(ptls, sizeof(void*), jl_weakref_type);
     wr->value = value;  // NOTE: wb not needed here
-    OBJ_PIN(wr)
     // Note: we are using MMTk's weak ref processing. If we switch to Julia's weak ref processing,
     // we need to make sure the value and the weak ref won't be moved (e.g. pin them)
     mmtk_add_weak_candidate(wr);

src/genericmemory.c

@@ -38,16 +38,13 @@ JL_DLLEXPORT jl_genericmemory_t *jl_alloc_genericmemory_unchecked(jl_ptls_t ptls
         data = (char*)jl_gc_managed_malloc(nbytes);
         tot = sizeof(jl_genericmemory_t) + sizeof(void*);
     }
-    m = (jl_genericmemory_t*)jl_gc_alloc(ptls, tot, mtype);
+    m = (jl_genericmemory_t*)jl_gc_alloc_nonmoving(ptls, tot, mtype);
     if (pooled) {
         data = (char*)m + JL_SMALL_BYTE_ALIGNMENT;
-        // Data is inlined and ptr is an internal pointer. We pin the object so the ptr will not be invalid.
-        OBJ_PIN(m);
     }
     else {
         int isaligned = 1; // jl_gc_managed_malloc is always aligned
         jl_gc_track_malloced_genericmemory(ptls, m, isaligned);
-        OBJ_PIN(m);
         jl_genericmemory_data_owner_field(m) = (jl_value_t*)m;
     }
     // length set by codegen
@@ -110,12 +107,11 @@ JL_DLLEXPORT jl_genericmemory_t *jl_string_to_genericmemory(jl_value_t *str)
         return (jl_genericmemory_t*)((jl_datatype_t*)jl_memory_uint8_type)->instance;
     jl_task_t *ct = jl_current_task;
     int tsz = sizeof(jl_genericmemory_t) + sizeof(void*);
-    jl_genericmemory_t *m = (jl_genericmemory_t*)jl_gc_alloc(ct->ptls, tsz, jl_memory_uint8_type);
+    jl_genericmemory_t *m = (jl_genericmemory_t*)jl_gc_alloc_nonmoving(ct->ptls, tsz, jl_memory_uint8_type);
     m->length = jl_string_len(str);
     m->ptr = jl_string_data(str);
     jl_genericmemory_data_owner_field(m) = str;
     OBJ_PIN(str);
-    OBJ_PIN(m); // FIXME: without this pin, make test-Tar fail with stress copying
     return m;
 }
 

src/julia_internal.h

@@ -585,10 +585,9 @@ JL_DLLEXPORT uintptr_t jl_get_buff_tag(void) JL_NOTSAFEPOINT;
 typedef void jl_gc_tracked_buffer_t; // For the benefit of the static analyzer
 STATIC_INLINE jl_gc_tracked_buffer_t *jl_gc_alloc_buf(jl_ptls_t ptls, size_t sz)
 {
-    jl_gc_tracked_buffer_t *buf = jl_gc_alloc(ptls, sz, (void*)jl_buff_tag);
+    jl_gc_tracked_buffer_t *buf = jl_gc_alloc_nonmoving(ptls, sz, (void*)jl_buff_tag);
     // FIXME: we might not need to pin buffers since the introduction of jl_genericmemory_t objects
     // but removing the pin below will currently fail an assertion in the binding
-    OBJ_PIN(buf);
     return buf;
 }