[PATCH] malloc: Use _int_free_chunk for remainders

[Wilco Dijkstra]

When splitting a chunk, release the tail part by calling _int_free_chunk.
This avoids inserting random blocks into tcache that were never requested
by the user.  Fragmentation will be worse if they are never used again.
Note if the tail is fairly small, we could avoid splitting it at all.
Also remove an oddly placed initialization of tcache in __libc_realloc.

Passes regress, OK for commit?

---

diff --git a/malloc/malloc.c b/malloc/malloc.c
index 55fb2ab0ecd5491591e0d04ae38a9bd1088af623..c71f5405e014ab27ef8aa42b8b39c9b9ae1ae152 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2646,7 +2646,7 @@ sysmalloc (INTERNAL_SIZE_T nb, mstate av)
 			CHUNK_HDR_SZ | PREV_INUSE);
               set_foot (chunk_at_offset (old_top, old_size), CHUNK_HDR_SZ);
               set_head (old_top, old_size | PREV_INUSE | NON_MAIN_ARENA);
-              _int_free (av, old_top, 1);
+              _int_free_chunk (av, old_top, chunksize (old_top), 1);
             }
           else
             {
@@ -2912,7 +2912,7 @@ sysmalloc (INTERNAL_SIZE_T nb, mstate av)
                       /* If possible, release the rest. */
                       if (old_size >= MINSIZE)
                         {
-                          _int_free (av, old_top, 1);
+                          _int_free_chunk (av, old_top, chunksize (old_top), 1);
                         }
                     }
                 }
@@ -3530,10 +3530,7 @@ __libc_realloc (void *oldmem, size_t bytes)
   if (chunk_is_mmapped (oldp))
     ar_ptr = NULL;
   else
-    {
-      MAYBE_INIT_TCACHE ();
-      ar_ptr = arena_for_chunk (oldp);
-    }
+    ar_ptr = arena_for_chunk (oldp);
 
   /* Little security check which won't hurt performance: the allocator
      never wraps around at the end of the address space.  Therefore
@@ -3608,7 +3605,7 @@ __libc_realloc (void *oldmem, size_t bytes)
 	  size_t sz = memsize (oldp);
 	  memcpy (newp, oldmem, sz);
 	  (void) tag_region (chunk2mem (oldp), sz);
-          _int_free (ar_ptr, oldp, 0);
+          _int_free_chunk (ar_ptr, oldp, chunksize (oldp), 0);
         }
     }
 
@@ -5057,7 +5054,7 @@ _int_realloc (mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
 	      (void) tag_region (oldmem, sz);
 	      newmem = tag_new_usable (newmem);
 	      memcpy (newmem, oldmem, sz);
-	      _int_free (av, oldp, 1);
+	      _int_free_chunk (av, oldp, chunksize (oldp), 1);
 	      check_inuse_chunk (av, newp);
 	      return newmem;
             }
@@ -5085,7 +5082,7 @@ _int_realloc (mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
                 (av != &main_arena ? NON_MAIN_ARENA : 0));
       /* Mark remainder as inuse so free() won't complain */
       set_inuse_bit_at_offset (remainder, remainder_size);
-      _int_free (av, remainder, 1);
+      _int_free_chunk (av, remainder, chunksize (remainder), 1);
     }
 
   check_inuse_chunk (av, newp);