Initial import

third_party/dlmalloc/malloc_trim.c

@@ -0,0 +1,31 @@
+#include "libc/mem/mem.h"
+#include "third_party/dlmalloc/dlmalloc.h"
+
+/**
+ * If possible, gives memory back to the system (via negative arguments
+ * to sbrk) if there is unused memory at the `high' end of the malloc
+ * pool or in unused MMAP segments. You can call this after freeing
+ * large blocks of memory to potentially reduce the system-level memory
+ * requirements of a program. However, it cannot guarantee to reduce
+ * memory. Under some allocation patterns, some large free blocks of
+ * memory will be locked between two used chunks, so they cannot be
+ * given back to the system.
+ *
+ * The `pad' argument to malloc_trim represents the amount of free
+ * trailing space to leave untrimmed. If this argument is zero, only the
+ * minimum amount of memory to maintain internal data structures will be
+ * left. Non-zero arguments can be supplied to maintain enough trailing
+ * space to service future expected allocations without having to
+ * re-obtain memory from the system.
+ *
+ * @return 1 if it actually released any memory, else 0
+ */
+int malloc_trim(size_t pad) {
+  int result = 0;
+  ensure_initialization();
+  if (!PREACTION(gm)) {
+    result = dlmalloc_sys_trim(gm, pad);
+    POSTACTION(gm);
+  }
+  return result;
+}