1 /* -----------------------------------------------------------------------------
2 * $Id: Block.h,v 1.13 2003/03/28 15:13:52 sof Exp $
4 * (c) The GHC Team, 1998-1999
6 * Block structure for the storage manager
8 * ---------------------------------------------------------------------------*/
13 /* The actual block and megablock-size constants are defined in
14 * includes/Constants.h, all constants here are derived from these.
17 /* Block related constants (BLOCK_SHIFT is defined in Constants.h) */
19 #define BLOCK_SIZE (1<<BLOCK_SHIFT)
20 #define BLOCK_SIZE_W (BLOCK_SIZE/sizeof(W_))
21 #define BLOCK_MASK (BLOCK_SIZE-1)
23 #define BLOCK_ROUND_UP(p) ((void *) (((W_)(p)+BLOCK_SIZE-1) & ~BLOCK_MASK))
24 #define BLOCK_ROUND_DOWN(p) ((void *) ((W_)(p) & ~BLOCK_MASK))
26 /* Megablock related constants (MBLOCK_SHIFT is defined in Constants.h) */
28 #define MBLOCK_SIZE (1<<MBLOCK_SHIFT)
29 #define MBLOCK_SIZE_W (MBLOCK_SIZE/sizeof(W_))
30 #define MBLOCK_MASK (MBLOCK_SIZE-1)
32 #define MBLOCK_ROUND_UP(p) ((void *)(((W_)(p)+MBLOCK_SIZE-1) & ~MBLOCK_MASK))
33 #define MBLOCK_ROUND_DOWN(p) ((void *)((W_)(p) & ~MBLOCK_MASK ))
35 /* The largest size an object can be before we give it a block of its
36 * own and treat it as an immovable object during GC, expressed as a
37 * fraction of BLOCK_SIZE.
39 #define LARGE_OBJECT_THRESHOLD ((nat)(BLOCK_SIZE * 8 / 10))
41 /* -----------------------------------------------------------------------------
42 * Block descriptor. This structure *must* be the right length, so we
43 * can do pointer arithmetic on pointers to it.
46 /* The block descriptor is 64 bytes on a 64-bit machine, and 32-bytes
47 * on a 32-bit machine.
50 typedef struct _bdescr {
51 StgPtr start; /* start addr of memory */
52 StgPtr free; /* first free byte of memory */
53 struct _bdescr *link; /* used for chaining blocks together */
55 struct _bdescr *back; /* used (occasionally) for doubly-linked lists*/
58 unsigned int gen_no; /* generation */
59 struct _step *step; /* step */
60 StgWord32 blocks; /* no. of blocks (if grp head, 0 otherwise) */
61 StgWord32 flags; /* block is in to-space */
62 #if SIZEOF_VOID_P == 8
63 StgWord32 _padding[2];
65 StgWord32 _padding[0];
69 #if SIZEOF_VOID_P == 8
70 #define BDESCR_SIZE 0x40
71 #define BDESCR_MASK 0x3f
72 #define BDESCR_SHIFT 6
74 #define BDESCR_SIZE 0x20
75 #define BDESCR_MASK 0x1f
76 #define BDESCR_SHIFT 5
79 #define BF_EVACUATED 1
82 /* Finding the block descriptor for a given block -------------------------- */
84 static inline bdescr *Bdescr(StgPtr p)
87 ((((W_)p & MBLOCK_MASK & ~BLOCK_MASK) >> (BLOCK_SHIFT-BDESCR_SHIFT))
88 | ((W_)p & ~MBLOCK_MASK)
92 /* Useful Macros ------------------------------------------------------------ */
94 /* Offset of first real data block in a megablock */
96 #define FIRST_BLOCK_OFF \
97 ((W_)BLOCK_ROUND_UP(BDESCR_SIZE * (MBLOCK_SIZE / BLOCK_SIZE)))
99 /* First data block in a given megablock */
101 #define FIRST_BLOCK(m) ((void *)(FIRST_BLOCK_OFF + (W_)(m)))
103 /* Last data block in a given megablock */
105 #define LAST_BLOCK(m) ((void *)(MBLOCK_SIZE-BLOCK_SIZE + (W_)(m)))
107 /* First real block descriptor in a megablock */
109 #define FIRST_BDESCR(m) \
110 ((bdescr *)((FIRST_BLOCK_OFF>>(BLOCK_SHIFT-BDESCR_SHIFT)) + (W_)(m)))
112 /* Number of usable blocks in a megablock */
114 #define BLOCKS_PER_MBLOCK ((MBLOCK_SIZE - FIRST_BLOCK_OFF) / BLOCK_SIZE)
116 /* How many blocks in this megablock group */
118 #define MBLOCK_GROUP_BLOCKS(n) \
119 (BLOCKS_PER_MBLOCK + (n-1) * (MBLOCK_SIZE / BLOCK_SIZE))
121 /* Compute the required size of a megablock group */
123 #define BLOCKS_TO_MBLOCKS(n) \
124 (1 + (W_)MBLOCK_ROUND_UP((n-BLOCKS_PER_MBLOCK) * BLOCK_SIZE) / MBLOCK_SIZE)