correctly track freed bytes in jl_genericmemory_to_string (#54331)

Master version of #54309.

Should fix #54275.

---------

Co-authored-by: Jameson Nash <vtjnash@gmail.com>
(cherry picked from commit 92ccc74)

src/gc.c

@@ -1139,6 +1139,12 @@ void jl_gc_count_allocd(size_t sz) JL_NOTSAFEPOINT
         jl_atomic_load_relaxed(&ptls->gc_num.allocd) + sz);
     jl_batch_accum_heap_size(ptls, sz);
 }
+
+void jl_gc_count_freed(size_t sz) JL_NOTSAFEPOINT
+{
+    jl_batch_accum_free_size(jl_current_task->ptls, sz);
+}
+
 // Only safe to update the heap inside the GC
 static void combine_thread_gc_counts(jl_gc_num_t *dest, int update_heap) JL_NOTSAFEPOINT
 {

src/gc.h

@@ -723,8 +723,6 @@ void gc_stats_big_obj(void);
 // For debugging
 void gc_count_pool(void);
 
-size_t jl_genericmemory_nbytes(jl_genericmemory_t *a) JL_NOTSAFEPOINT;
-
 JL_DLLEXPORT void jl_enable_gc_logging(int enable);
 JL_DLLEXPORT int jl_is_gc_logging_enabled(void);
 JL_DLLEXPORT uint32_t jl_get_num_stack_mappings(void);

src/genericmemory.c

@@ -161,9 +161,9 @@ JL_DLLEXPORT jl_genericmemory_t *jl_ptr_to_genericmemory(jl_value_t *mtype, void
     m = (jl_genericmemory_t*)jl_gc_alloc(ct->ptls, tsz, mtype);
     m->ptr = data;
     m->length = nel;
-    jl_genericmemory_data_owner_field(m) = NULL;
-    int isaligned = 0;  // TODO: allow passing memalign'd buffers
+    jl_genericmemory_data_owner_field(m) = own_buffer ? (jl_value_t*)m : NULL;
     if (own_buffer) {
+        int isaligned = 0;  // TODO: allow passing memalign'd buffers
         jl_gc_track_malloced_genericmemory(ct->ptls, m, isaligned);
         jl_gc_count_allocd(nel*elsz);
     }
@@ -208,8 +208,11 @@ JL_DLLEXPORT jl_value_t *jl_genericmemory_to_string(jl_genericmemory_t *m, size_
         JL_GC_PUSH1(&o);
         jl_value_t *str = jl_pchar_to_string((const char*)m->ptr, len);
         JL_GC_POP();
+        if (how == 1) // TODO: we might like to early-call jl_gc_free_memory here instead actually, but hopefully `m` will die soon
+            jl_gc_count_freed(mlength);
         return str;
     }
+    // n.b. how == 0 is always pool-allocated, so the freed bytes are computed from the pool not the object
     return jl_pchar_to_string((const char*)m->ptr, len);
 }
 

src/julia.h

@@ -1148,8 +1148,8 @@ STATIC_INLINE jl_value_t *jl_svecset(
 /*
   how - allocation style
   0 = data is inlined
-  1 = owns the gc-managed data, exclusively
-  2 = malloc-allocated pointer (may or may not own it)
+  1 = owns the gc-managed data, exclusively (will free it)
+  2 = malloc-allocated pointer (does not own it)
   3 = has a pointer to the object that owns the data pointer
 */
 STATIC_INLINE int jl_genericmemory_how(jl_genericmemory_t *m) JL_NOTSAFEPOINT

src/julia_internal.h

@@ -616,7 +616,9 @@ JL_DLLEXPORT int64_t jl_gc_diff_total_bytes(void) JL_NOTSAFEPOINT;
 JL_DLLEXPORT int64_t jl_gc_sync_total_bytes(int64_t offset) JL_NOTSAFEPOINT;
 void jl_gc_track_malloced_array(jl_ptls_t ptls, jl_array_t *a) JL_NOTSAFEPOINT;
 void jl_gc_track_malloced_genericmemory(jl_ptls_t ptls, jl_genericmemory_t *m, int isaligned) JL_NOTSAFEPOINT;
+size_t jl_genericmemory_nbytes(jl_genericmemory_t *a) JL_NOTSAFEPOINT;
 void jl_gc_count_allocd(size_t sz) JL_NOTSAFEPOINT;
+void jl_gc_count_freed(size_t sz) JL_NOTSAFEPOINT;
 void jl_gc_run_all_finalizers(jl_task_t *ct);
 void jl_release_task_stack(jl_ptls_t ptls, jl_task_t *task);
 void jl_gc_add_finalizer_(jl_ptls_t ptls, void *v, void *f) JL_NOTSAFEPOINT;