Changeset 80f2885b in rtems

Timestamp:

05/20/05 19:15:41 (18 years ago)

Author:

Joel Sherrill <joel.sherrill@…>

Branches:

4.10, 4.11, 4.8, 4.9, 5, master

Children:

5c1af4c

Parents:

207a979

Message:

2005-05-14 Sergei Organov <osv@…>

PR 746/rtems
Optimize realloc(). The problem is that realloc() can neither grow
nor shrink efficiently the current memory region without support
from underlying heap/region modules. The patch introduces one new
routine for each of heap and region modules, _Heap_Resize_block(),
and rtems_region_resize_segment(), respectively, and uses the
latter to optimize realloc().

The implementation of _Heap_Resize_block() lead to changing of the
heap allocation strategy: now the heap manager, when splits larger
free block into used and new free parts, makes the first part of
the block used, not the last one as it was before. Due to this new
strategy, _Heap_Resize_block() never needs to change the user
pointer.

Caveat: unlike previous heap implementation, first few bytes of
the contents of the memory allocated from the heap are now almost
never all zero. This can trigger bugs in client code that have not
been visible before this patch.

• libcsupport/src/malloc.c (realloc): try to resize segment in place using new rtems_region_resize_segment() routine before falling back to the malloc()/free() method.
• score/src/heap.c: (_Heap_Initialize): change initial heap layout to reflect new allocation strategy of using of the lower part of a previously free block when splitting it for the purpose of allocation. (_Heap_Block_allocate): when split, make the lower part used, and leave the upper part free. Return type changed from Heap_Block* to uint32_t.
• score/include/rtems/score/heap.h: (Heap_Statistics): added 'resizes' field. (Heap_Resize_status): new enum. (_Heap_Resize_block): new routine. (_Heap_Block_allocate): return type changed from Heap_Block* to uint32_t.
• score/src/heapwalk.c: reflect new heap layout in checks.
• score/src/heapsizeofuserarea.c: more assertions added.
• score/src/heapresizeblock.c: new file. (_Heap_Resize_block): new routine.
• score/src/heapfree.c: reverse the checks _Heap_Is_block_in() and _Heap_Is_prev_used() on entry to be in this order.
• score/src/heapallocate.c, score/src/heapallocatealigned.c: ignore return value of _Heap_Block_allocate().
• score/Makefile.am (HEAP_C_FILES): added src/heapresizeblock.c.
• rtems/include/rtems/rtems/region.h: (rtems_region_resize_segment): new interface routine. (_Region_Process_queue): new internal routine called from rtems_region_resize_segment() and rtems_region_return_segment().
• rtems/src/regionreturnsegment.c: move queue management code into the new internal routine _Region_Process_queue() and call it.

• rtems/src/regionresizesegment.c: new file. (rtems_region_resize_segment): new interface routine.
• rtems/src/regionprocessqueue.c: new file. (_Region_Process_queue): new internal routine containing queue management code factored out from 'regionreturnsegment.c'.
• rtems/Makefile.am (REGION_C_FILES): Added src/regionresizesegment.c, and src/regionprocessqueue.c.
• ada/rtems.adb, ada/rtems.ads: Added Region_Resize_Segment.

Files:

• c/src/ada/rtems.adb (modified) (1 diff)
• c/src/ada/rtems.ads (modified) (1 diff)
• cpukit/ChangeLog (modified) (1 diff)
• cpukit/ada/rtems.adb (modified) (1 diff)
• cpukit/ada/rtems.ads (modified) (1 diff)
• cpukit/libcsupport/src/malloc.c (modified) (2 diffs)
• cpukit/rtems/Makefile.am (modified) (1 diff)
• cpukit/rtems/include/rtems/rtems/region.h (modified) (1 diff)
• cpukit/rtems/src/regionprocessqueue.c (added)
• cpukit/rtems/src/regionresizesegment.c (added)
• cpukit/rtems/src/regionreturnsegment.c (modified) (3 diffs)
• cpukit/score/Makefile.am (modified) (1 diff)
• cpukit/score/include/rtems/score/heap.h (modified) (5 diffs)
• cpukit/score/src/heap.c (modified) (11 diffs)
• cpukit/score/src/heapallocate.c (modified) (1 diff)
• cpukit/score/src/heapallocatealigned.c (modified) (1 diff)
• cpukit/score/src/heapfree.c (modified) (2 diffs)
• cpukit/score/src/heapresizeblock.c (added)
• cpukit/score/src/heapsizeofuserarea.c (modified) (2 diffs)
• cpukit/score/src/heapwalk.c (modified) (2 diffs)

c/src/ada/rtems.adb

@@ -1506 +1506 @@
          Size_Base'Unchecked_Access
       );
-      Size := SIZE_Base;
+      Size := Size_Base;
 
    end Region_Get_Segment_Size;
  
+   procedure Region_Resize_Segment (
+      ID         : in     RTEMS.ID;
+      Segment    : in     RTEMS.Address;
+      Size       : in     RTEMS.Unsigned32;
+      Old_Size   :    out RTEMS.Unsigned32;
+      Result     :    out RTEMS.Status_Codes
+   ) is
+      function Region_Resize_Segment_Base (
+         ID       : RTEMS.ID;
+         Segment  : RTEMS.Address;
+         Size     : RTEMS.Unsigned32;
+         Old_Size : access RTEMS.Unsigned32
+      )  return RTEMS.Status_Codes;
+      pragma Import (C, Region_Resize_Segment_Base,
+         "rtems_region_get_segment_size");
+      Old_Size_Base : aliased RTEMS.Unsigned32;
+   begin
+ 
+      Result := Region_Resize_Segment_Base (
+         ID,
+         Segment,
+         Size,
+         Size_Base'Unchecked_Access
+      );
+      Old_Size := Old_Size_Base;
+
+   end Region_Resize_Segment;
+
    procedure Region_Return_Segment (
       ID      : in     RTEMS.ID;

c/src/ada/rtems.ads

@@ -1300 +1300 @@
    );
 
+   procedure Region_Resize_Segment (
+      ID         : in     RTEMS.ID;
+      Segment    : in     RTEMS.Address;
+      Old_Size   : in     RTEMS.Unsigned32;
+      Size       :    out RTEMS.Unsigned32;
+      Result     :    out RTEMS.Status_Codes
+   );
+
    procedure Region_Return_Segment (
       ID      : in     RTEMS.ID;

cpukit/ChangeLog

@@ +1 @@
+2005-05-14  Sergei Organov  <osv@topconrd.ru>
+
+        PR 746/rtems
+        Optimize realloc(). The problem is that realloc() can neither grow
+        nor shrink efficiently the current memory region without support
+        from underlying heap/region modules. The patch introduces one new
+        routine for each of heap and region modules, _Heap_Resize_block(),
+        and rtems_region_resize_segment(), respectively, and uses the
+        latter to optimize realloc().
+
+        The implementation of _Heap_Resize_block() lead to changing of the
+        heap allocation strategy: now the heap manager, when splits larger
+        free block into used and new free parts, makes the first part of
+        the block used, not the last one as it was before. Due to this new
+        strategy, _Heap_Resize_block() never needs to change the user
+        pointer.
+
+        Caveat: unlike previous heap implementation, first few bytes of
+        the contents of the memory allocated from the heap are now almost
+        never all zero. This can trigger bugs in client code that have not
+        been visible before this patch.
+
+        * libcsupport/src/malloc.c (realloc): try to resize segment in
+        place using new rtems_region_resize_segment() routine before
+        falling back to the malloc()/free() method.
+        * score/src/heap.c:
+        (_Heap_Initialize): change initial heap layout to reflect new
+        allocation strategy of using of the lower part of a previously
+        free block when splitting it for the purpose of allocation.
+        (_Heap_Block_allocate): when split, make the lower part used, and
+        leave the upper part free. Return type changed from Heap_Block* to
+        uint32_t.
+        * score/include/rtems/score/heap.h:
+        (Heap_Statistics): added 'resizes' field.
+        (Heap_Resize_status): new enum.
+        (_Heap_Resize_block): new routine.
+        (_Heap_Block_allocate): return type changed from Heap_Block* to
+        uint32_t.
+        * score/src/heapwalk.c: reflect new heap layout in checks.
+        * score/src/heapsizeofuserarea.c: more assertions added.
+        * score/src/heapresizeblock.c: new file.
+        (_Heap_Resize_block): new routine.
+        * score/src/heapfree.c: reverse the checks _Heap_Is_block_in() and
+        _Heap_Is_prev_used() on entry to be in this order.
+        * score/src/heapallocate.c, score/src/heapallocatealigned.c:
+        ignore return value of _Heap_Block_allocate(). 
+        * score/Makefile.am (HEAP_C_FILES): added src/heapresizeblock.c.
+        * rtems/include/rtems/rtems/region.h:
+        (rtems_region_resize_segment): new interface routine.
+        (_Region_Process_queue): new internal routine called from
+        rtems_region_resize_segment() and rtems_region_return_segment().
+        * rtems/src/regionreturnsegment.c: move queue management code into
+        the new internal routine _Region_Process_queue() and call it.
+
+        * rtems/src/regionresizesegment.c: new file.
+        (rtems_region_resize_segment): new interface routine.
+        * rtems/src/regionprocessqueue.c: new file.
+        (_Region_Process_queue): new internal routine containing queue
+        management code factored out from 'regionreturnsegment.c'.
+        * rtems/Makefile.am (REGION_C_FILES): Added
+        src/regionresizesegment.c, and src/regionprocessqueue.c.
+        * ada/rtems.adb, ada/rtems.ads: Added Region_Resize_Segment.
+
 2005-05-20      Eric Norum <norume@aps.anl.gov>
 

cpukit/ada/rtems.adb

@@ -1506 +1506 @@
          Size_Base'Unchecked_Access
       );
-      Size := SIZE_Base;
+      Size := Size_Base;
 
    end Region_Get_Segment_Size;
  
+   procedure Region_Resize_Segment (
+      ID         : in     RTEMS.ID;
+      Segment    : in     RTEMS.Address;
+      Size       : in     RTEMS.Unsigned32;
+      Old_Size   :    out RTEMS.Unsigned32;
+      Result     :    out RTEMS.Status_Codes
+   ) is
+      function Region_Resize_Segment_Base (
+         ID       : RTEMS.ID;
+         Segment  : RTEMS.Address;
+         Size     : RTEMS.Unsigned32;
+         Old_Size : access RTEMS.Unsigned32
+      )  return RTEMS.Status_Codes;
+      pragma Import (C, Region_Resize_Segment_Base,
+         "rtems_region_get_segment_size");
+      Old_Size_Base : aliased RTEMS.Unsigned32;
+   begin
+ 
+      Result := Region_Resize_Segment_Base (
+         ID,
+         Segment,
+         Size,
+         Size_Base'Unchecked_Access
+      );
+      Old_Size := Old_Size_Base;
+
+   end Region_Resize_Segment;
+
    procedure Region_Return_Segment (
       ID      : in     RTEMS.ID;

cpukit/ada/rtems.ads

@@ -1300 +1300 @@
    );
 
+   procedure Region_Resize_Segment (
+      ID         : in     RTEMS.ID;
+      Segment    : in     RTEMS.Address;
+      Old_Size   : in     RTEMS.Unsigned32;
+      Size       :    out RTEMS.Unsigned32;
+      Result     :    out RTEMS.Status_Codes
+   );
+
    procedure Region_Return_Segment (
       ID      : in     RTEMS.ID;

cpukit/libcsupport/src/malloc.c

@@ -309 +309 @@
 
   /*
-   * Continue with calloc().
+   * Continue with realloc().
    */
   if ( !ptr )
@@ -316 +316 @@
   if ( !size ) {
     free( ptr );
+    return (void *) 0;
+  }
+
+  status =
+    rtems_region_resize_segment( RTEMS_Malloc_Heap, ptr, size, &old_size );
+
+  if( status == RTEMS_SUCCESSFUL ) {
+    return ptr;
+  }
+  else if ( status != RTEMS_UNSATISFIED ) {
+    errno = EINVAL;
     return (void *) 0;
   }

cpukit/rtems/Makefile.am

@@ -106 +106 @@
     src/regionextend.c src/regiongetsegment.c src/regiongetsegmentsize.c \
     src/regionident.c src/regionreturnsegment.c src/regiongetinfo.c \
-    src/regiongetfreeinfo.c
+    src/regiongetfreeinfo.c src/regionresizesegment.c \
+    src/regionprocessqueue.c
 
 PARTITION_C_FILES = src/part.c src/partcreate.c src/partdelete.c \

cpukit/rtems/include/rtems/rtems/region.h

@@ -233 +233 @@
 );
 
+/*
+ *  rtems_region_resize_segment
+ *
+ *  DESCRIPTION:
+ *
+ *  This routine implements the rtems_region_resize_segment directive.  It
+ *  tries to resize segment in the region associated with 'id' to the new size
+ *  'size' in place. The first 'size' or old size bytes of the segment
+ *  (whatever is less) are guaranteed to remain unmodified. The segment must
+ *  have been previously allocated from the same region.  If resizing the
+ *  segment results in enough memory being available to satisfy the
+ *  rtems_region_get_segment of the first blocked task, then that task and as
+ *  many subsequent tasks as possible will be unblocked with their requests
+ *  satisfied.
+ *  Returns:
+ *    RTEMS_SUCCESSFUL  - operation successful
+ *    RTEMS_UNSATISFIED - the segment can't be resized in place
+ *    any other code    - failure.
+ *  On RTEMS_SUCCESSFUL or RTEMS_UNSATISFIED exit it returns into the
+ *  'old_size' the old size in bytes of the user memory area of the specified
+ *  segment.
+ */
+
+rtems_status_code rtems_region_resize_segment(
+  Objects_Id  id,
+  void       *segment,
+  size_t      size,
+  size_t     *old_size
+);
+
 #ifndef __RTEMS_APPLICATION__
 #include <rtems/rtems/region.inl>
+extern void _Region_Process_queue(Region_Control *the_region);
 #endif
 #if defined(RTEMS_MULTIPROCESSING)

cpukit/rtems/src/regionreturnsegment.c

@@ -56 +56 @@
 {
   register Region_Control *the_region;
-  Thread_Control          *the_thread;
   Objects_Locations        location;
-  void                   **the_segment;
 #ifdef RTEMS_REGION_FREE_SHRED_PATTERN
   uint32_t                 size;
@@ -82 +80 @@
 #ifdef RTEMS_REGION_FREE_SHRED_PATTERN
       if ( _Heap_Size_of_user_area( &the_region->Memory, segment, &size ) ) {
-        memset(segment, (RTEMS_REGION_FREE_SHRED_PATTERN & 0xFF), size);
+        memset( segment, (RTEMS_REGION_FREE_SHRED_PATTERN & 0xFF), size );
       } else {
         _RTEMS_Unlock_allocator();
@@ -100 +98 @@
       the_region->number_of_used_blocks -= 1;
 
-      /*
-       *  Switch from using the memory allocation mutex to using a
-       *  dispatching disabled critical section.  We have to do this
-       *  because this thread may unblock one or more threads that were
-       *  waiting on memory.
-       *
-       *  NOTE: The following loop is O(n) where n is the number of
-       *        threads whose memory request is satisfied.
-       */
-      _RTEMS_Unlock_allocator();
-      _Thread_Disable_dispatch();
-
-      for ( ; ; ) {
-        the_thread = _Thread_queue_First( &the_region->Wait_queue );
-
-        if ( the_thread == NULL )
-           break;
-
-        the_segment = (void **) _Region_Allocate_segment(
-           the_region,
-           the_thread->Wait.count
-        );
-
-        if ( the_segment == NULL )
-           break;
-
-        *(void **)the_thread->Wait.return_argument = the_segment;
-        the_region->number_of_used_blocks += 1;
-        _Thread_queue_Extract( &the_region->Wait_queue, the_thread );
-        the_thread->Wait.return_code = RTEMS_SUCCESSFUL;
-      }
-      _Thread_Enable_dispatch();
+      _Region_Process_queue(the_region); /* unlocks allocator internally */
 
       return RTEMS_SUCCESSFUL;

cpukit/score/Makefile.am

@@ -99 +99 @@
 HEAP_C_FILES = src/heap.c src/heapallocate.c src/heapextend.c src/heapfree.c \
     src/heapsizeofuserarea.c src/heapwalk.c src/heapgetinfo.c \
-    src/heapgetfreeinfo.c src/heapallocatealigned.c
+    src/heapgetfreeinfo.c src/heapallocatealigned.c \
+    src/heapresizeblock.c
 
 OBJECT_C_FILES = src/object.c src/objectallocate.c \

cpukit/score/include/rtems/score/heap.h

@@ -166 +166 @@
   /** total number of suceessful calls to free */
   uint32_t frees;
+  /** total number of successful resizes */
+  uint32_t resizes;
 } Heap_Statistics;
 
@@ -191 +193 @@
 
 /**
- *  Status codes for heap_extend
+ *  Status codes for _Heap_Extend
  */
 
@@ -199 +201 @@
   HEAP_EXTEND_NOT_IMPLEMENTED
 } Heap_Extend_status;
+
+/**
+ *  Status codes for _Heap_Resize_block
+ */
+
+typedef enum {
+  HEAP_RESIZE_SUCCESSFUL,
+  HEAP_RESIZE_UNSATISFIED,
+  HEAP_RESIZE_FATAL_ERROR
+} Heap_Resize_status;
 
 /**
@@ -327 +339 @@
 );
 
+/*
+ *  This function tries to resize in place the block that is pointed to by the
+ *  @a starting_address to the new @a size.
+ *
+ *  @param the_heap (in) is the heap to operate upon
+ *  @param starting_address (in) is the starting address of the user block
+ *         to be resized
+ *  @param size (in) is the new size
+ *  @param old_mem_size (in) points to a user area to return the size of the
+ *         user memory area of the block before resizing.
+ *  @param avail_mem_size (in) points to a user area to return the size of
+ *         the user memory area of the free block that has been enlarged or
+ *         created due to resizing, 0 if none.
+ *  @return HEAP_RESIZE_SUCCESSFUL if successfully able to resize the block,
+ *          HEAP_RESIZE_UNSATISFIED if the block can't be resized in place,
+ *          HEAP_RESIZE_FATAL_ERROR if failure
+ *  @return *old_mem_size filled in with the size of the user memory area of
+ *          the block before resizing.
+ *  @return *avail_mem_size filled in with the size of the user memory area
+ *          of the free block that has been enlarged or created due to
+ *          resizing, 0 if none.
+ */
+Heap_Resize_status _Heap_Resize_block(
+  Heap_Control *the_heap,
+  void         *starting_address,
+  uint32_t     size,
+  uint32_t     *old_mem_size,
+  uint32_t     *avail_mem_size
+);
+
 /**
  *  This routine returns the block of memory which begins
@@ -405 +447 @@
   uint32_t min_size);
 
-extern Heap_Block* _Heap_Block_allocate(
+extern uint32_t _Heap_Block_allocate(
   Heap_Control* the_heap,
   Heap_Block* the_block,

cpukit/score/src/heap.c

@@ -45 +45 @@
  *            |       size < page_size         |
  *         0  +--------------------------------+ <- first block
- *            |  prev_size = 1 (arbitrary)     |
+ *            |  prev_size = page_size         |
  *         4  +--------------------------------+
  *            |  size = size0              | 1 |
@@ -60 +60 @@
  *            |  prev_size = size0             |
  *        +4  +--------------------------------+
- *            |  size = 0 (arbitrary)      | 0 | <- prev block is free
+ *            |  size = page_size          | 0 | <- prev block is free
  *        +8  +--------------------------------+ <- aligned on page_size
  *            |  unused space due to alignment |
@@ -75 +75 @@
  *            |  unused space due to alignment |
  *            |       size < page_size         |
- *         0  +--------------------------------+ <- first block
- *            |  prev_size = 1 (arbitrary)     |
+ *         0  +--------------------------------+ <- used block
+ *            |  prev_size = page_size         |
  *         4  +--------------------------------+
- *            |  size = S = size0 - BSIZE  | 1 |
- *         8  +---------------------+----------+ <- aligned on page_size
- *            |  next = HEAP_TAIL   |          |
- *        12  +---------------------+          |
- *            |  prev = HEAP_HEAD   |  memory  |
- *            +---------------------+          |
- *            |                     available  |
- *            |                                |
- *            |                for allocation  |
- *            |                                |
- *         S  +--------------------------------+ <- used block
- *            |  prev_size = size0 - BSIZE     |
- *        +4  +--------------------------------+
- *            |  size = BSIZE              | 0 | <- prev block is free
- *        +8  +--------------------------------+ <- aligned on page_size
+ *            |  size = BSIZE              | 1 | <- prev block is used
+ *         8  +--------------------------------+ <- aligned on page_size
  *            |              .                 | Pointer returned to the user
- *            |              .                 | is (S+8) for _Heap_Allocate()
+ *            |              .                 | is 8 for _Heap_Allocate()
  *            |              .                 | and is in range
- * S + 8 +    |         user-accessible        | [S+8,S+8+page_size) for
- *   page_size+- - -                      - - -+ _Heap_Allocate_aligned()
+ * 8 +        |         user-accessible        | [8,8+page_size) for
+ *  page_size +- - -                      - - -+ _Heap_Allocate_aligned()
  *            |             area               |
  *            |              .                 |
- * S + BSIZE  +- - - - -     .        - - - - -+ <- last dummy block
+ *     BSIZE  +- - - - -     .        - - - - -+ <- free block
  *            |              .                 |
- *        +4  +--------------------------------+
- *            |  size = 0 (arbitrary)      | 1 | <- prev block is used
- *        +8  +--------------------------------+ <- aligned on page_size
+ * BSIZE  +4  +--------------------------------+
+ *            |  size = S = size0 - BSIZE  | 1 | <- prev block is used
+ * BSIZE  +8  +-------------------+------------+ <- aligned on page_size
+ *            |  next = HEAP_TAIL |            |
+ * BSIZE +12  +-------------------+            |
+ *            |  prev = HEAP_HEAD |     memory |
+ *            +-------------------+            |
+ *            |                   .  available |
+ *            |                   .            |
+ *            |                   .        for |
+ *            |                   .            |
+ * BSIZE +S+0 +-------------------+ allocation + <- last dummy block
+ *            |  prev_size = S    |            |
+ *       +S+4 +-------------------+------------+
+ *            |  size = page_size          | 0 | <- prev block is free
+ *       +S+8 +--------------------------------+ <- aligned on page_size
  *            |  unused space due to alignment |
  *            |       size < page_size         |
@@ -161 +161 @@
   the_block = (Heap_Block *) aligned_start;
 
-  the_block->prev_size = HEAP_PREV_USED;
+  the_block->prev_size = page_size;
   the_block->size = the_size | HEAP_PREV_USED;
   the_block->next = _Heap_Tail( the_heap );
@@ -176 +176 @@
   the_heap->final = the_block;       /* Permanent final block of the heap */
   the_block->prev_size = the_size;   /* Previous block is free */
-  the_block->size = 0;  /* This is the only block with size=0  */
+  the_block->size = page_size;
 
   stats->size = size;
@@ -188 +188 @@
   stats->searches = 0;
   stats->frees = 0;
+  stats->resizes = 0;
   stats->instance = instance++;
 
@@ -214 +215 @@
   _Heap_Align_up(&block_size, page_size);
   if(block_size < min_size) block_size = min_size;
+  /* 'block_size' becomes <= 'size' if and only if overflow occured. */
   return (block_size > size) ? block_size : 0;
 }
@@ -219 +221 @@
 /*
  * Allocate block of size 'alloc_size' from 'the_block' belonging to
- * 'the_heap'. Either split 'the_block' or allocate it entirely.
- * Return the block allocated.
- */
-Heap_Block* _Heap_Block_allocate(
+ * 'the_heap'. Split 'the_block' if possible, otherwise allocate it entirely.
+ * When split, make the lower part used, and leave the upper part free.
+ * Return the size of allocated block.
+ */
+unsigned32 _Heap_Block_allocate(
   Heap_Control* the_heap,
   Heap_Block* the_block,
@@ -234 +237 @@
   _HAssert(_Heap_Is_aligned(alloc_size, the_heap->page_size));
   _HAssert(alloc_size <= block_size);
+  _HAssert(_Heap_Is_prev_used(the_block));
 
   if(the_rest >= the_heap->min_block_size) {
-    /* Split the block so that lower part is still free, and upper part
-       becomes used. */
-    the_block->size = the_rest | HEAP_PREV_USED;
-    the_block = _Heap_Block_at(the_block, the_rest);
-    the_block->prev_size = the_rest;
-    the_block->size = alloc_size;
+    /* Split the block so that upper part is still free, and lower part
+       becomes used. This is slightly less optimal than leaving lower part
+       free as it requires replacing block in the free blocks list, but it
+       makes it possible to reuse this code in the _Heap_Resize_block(). */
+    Heap_Block *next_block = _Heap_Block_at(the_block, alloc_size);
+    _Heap_Block_replace(the_block, next_block);
+    the_block->size = alloc_size | HEAP_PREV_USED;
+    next_block->size = the_rest | HEAP_PREV_USED;
+    _Heap_Block_at(next_block, the_rest)->prev_size = the_rest;
   }
   else {
@@ -249 +256 @@
     _Heap_Block_remove(the_block);
     alloc_size = block_size;
+    _Heap_Block_at(the_block, alloc_size)->size |= HEAP_PREV_USED;
     stats->free_blocks -= 1;
   }
-  /* Mark the block as used (in the next block). */
-  _Heap_Block_at(the_block, alloc_size)->size |= HEAP_PREV_USED;
   /* Update statistics */
   stats->free_size -= alloc_size;
@@ -258 +264 @@
     stats->min_free_size = stats->free_size;
   stats->used_blocks += 1;
-  return the_block;
+  return alloc_size;
 }

cpukit/score/src/heapallocate.c

@@ -63 +63 @@
        result of the comparison. */
     if(the_block->size >= the_size) {
-      the_block = _Heap_Block_allocate(the_heap, the_block, the_size );
+      (void)_Heap_Block_allocate(the_heap, the_block, the_size );
 
       ptr = _Heap_User_area(the_block);

cpukit/score/src/heapallocatealigned.c

@@ -173 +173 @@
           _HAssert(_Heap_Is_aligned_ptr((void*)aligned_user_addr, alignment));
 
-          the_block =
-            _Heap_Block_allocate(the_heap, the_block, alloc_size);
+          (void)_Heap_Block_allocate(the_heap, the_block, alloc_size);
 
           stats->searches += search_count + 1;

cpukit/score/src/heapfree.c

@@ -52 +52 @@
   if ( !_Heap_Is_block_in( the_heap, the_block ) ) {
     _HAssert(starting_address == NULL);
+    _HAssert(FALSE);
     return( FALSE );
   }
@@ -58 +59 @@
   next_block = _Heap_Block_at( the_block, the_size );
 
-  if ( !_Heap_Is_prev_used( next_block ) ) {
+  if ( !_Heap_Is_block_in( the_heap, next_block ) ) {
     _HAssert(FALSE);
     return( FALSE );
   }
 
-  if ( !_Heap_Is_block_in( the_heap, next_block ) ) {
+  if ( !_Heap_Is_prev_used( next_block ) ) {
     _HAssert(FALSE);
     return( FALSE );

cpukit/score/src/heapsizeofuserarea.c

@@ -56 +56 @@
   _Heap_Start_of_block( the_heap, starting_address, &the_block );
 
+  _HAssert(_Heap_Is_block_in( the_heap, the_block ));
   if ( !_Heap_Is_block_in( the_heap, the_block ) )
     return( FALSE );
@@ -62 +63 @@
   next_block = _Heap_Block_at( the_block, the_size );
 
+  _HAssert(_Heap_Is_block_in( the_heap, next_block ));
+  _HAssert(_Heap_Is_prev_used( next_block ));
   if (
     !_Heap_Is_block_in( the_heap, next_block ) ||

cpukit/score/src/heapwalk.c

@@ -88 +88 @@
   }
 
-  if (the_block->prev_size != HEAP_PREV_USED) {
-    printf("PASS: %d !prev_size of 1st block isn't HEAP_PREV_USED\n", source);
+  if (the_block->prev_size != the_heap->page_size) {
+    printf("PASS: %d !prev_size of 1st block isn't page_size\n", source);
     error = 1;
   }
@@ -163 +163 @@
   }
 
-  if (_Heap_Block_size(the_block) != 0) {
-    printf("PASS: %d !last block's size isn't 0\n", source);
+  if (_Heap_Block_size(the_block) != the_heap->page_size) {
+    printf("PASS: %d !last block's size isn't page_size\n", source);
     error = 1;
   }