1 files changed, 10 insertions, 0 deletions
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 2a61c8b..ef8c794 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -1100,6 +1100,8 @@ static void munmap_chunk(mchunkptr p);
 static mchunkptr mremap_chunk(mchunkptr p, size_t new_size);
 #endif
 
+static size_t musable (void *mem);
+
 /* ------------------ MMAP support ------------------  */
 
 
@@ -3396,6 +3398,14 @@ __libc_realloc (void *oldmem, size_t bytes)
   if (__glibc_unlikely (mtag_enabled))
     *(volatile char*) oldmem;
 
+  /* Return the chunk as is whenever possible, i.e. there's enough usable space
+     but not so much that we end up fragmenting the block.  We use the trim
+     threshold as the heuristic to decide the latter.  */
+  size_t usable = musable (oldmem);
+  if (bytes <= usable
+      && (unsigned long) (usable - bytes) <= mp_.trim_threshold)
+    return oldmem;
+
   /* chunk corresponding to oldmem */
   const mchunkptr oldp = mem2chunk (oldmem);
   /* its size */