#include "Storage.h"
#include "RtsUtils.h"
#include "BlockAlloc.h"
+#include "OSMem.h"
#include <string.h>
static void initMBlock(void *mblock);
-// The free_list is kept sorted by size, smallest first.
-// In THREADED_RTS mode, the free list is protected by sm_mutex.
-
/* -----------------------------------------------------------------------------
Implementation notes
The following fields are not used by the allocator:
bd->flags
bd->gen_no
- bd->step
+ bd->gen
+ bd->dest
Exceptions: we don't maintain invariants for all the blocks within a
group on the free list, because it is expensive to modify every
~~~~~~~~~~
Preliminaries:
- - most allocations are for small blocks
+ - most allocations are for a small number of blocks
- sometimes the OS gives us new memory backwards in the address
space, sometimes forwards, so we should not be biased towards
any particular layout in the address space
--------------------------------------------------------------------------- */
+/* ---------------------------------------------------------------------------
+ WATCH OUT FOR OVERFLOW
+
+ Be very careful with integer overflow here. If you have an
+ expression like (n_blocks * BLOCK_SIZE), and n_blocks is an int or
+ a nat, then it will very likely overflow on a 64-bit platform.
+ Always cast to StgWord (or W_ for short) first: ((W_)n_blocks * BLOCK_SIZE).
+
+ --------------------------------------------------------------------------- */
+
#define MAX_FREE_LIST 9
+// In THREADED_RTS mode, the free list is protected by sm_mutex.
+
static bdescr *free_list[MAX_FREE_LIST];
static bdescr *free_mblock_list;
if (best)
{
// we take our chunk off the end here.
- nat best_mblocks = BLOCKS_TO_MBLOCKS(best->blocks);
+ StgWord best_mblocks = BLOCKS_TO_MBLOCKS(best->blocks);
bd = FIRST_BDESCR((StgWord8*)MBLOCK_ROUND_DOWN(best) +
(best_mblocks-mblocks)*MBLOCK_SIZE);
// only the bdescrs of the first MB are required to be initialised
initGroup(bd);
+ IF_DEBUG(sanity,memset(bd->start, 0xaa, bd->blocks * BLOCK_SIZE));
IF_DEBUG(sanity, checkFreeListSanity());
return bd;
}
if (ln == MAX_FREE_LIST) {
#if 0
- if ((mblocks_allocated * MBLOCK_SIZE_W - n_alloc_blocks * BLOCK_SIZE_W) > (1024*1024)/sizeof(W_)) {
+ if (((W_)mblocks_allocated * MBLOCK_SIZE_W - (W_)n_alloc_blocks * BLOCK_SIZE_W) > (1024*1024)/sizeof(W_)) {
debugBelch("Fragmentation, wanted %d blocks:", n);
RtsFlags.DebugFlags.block_alloc = 1;
checkFreeListSanity();
barf("allocGroup: free list corrupted");
}
initGroup(bd); // initialise it
+ IF_DEBUG(sanity,memset(bd->start, 0xaa, bd->blocks * BLOCK_SIZE));
IF_DEBUG(sanity, checkFreeListSanity());
ASSERT(bd->blocks == n);
return bd;
ASSERT(p->free != (P_)-1);
p->free = (void *)-1; /* indicates that this block is free */
- p->step = NULL;
+ p->gen = NULL;
p->gen_no = 0;
/* fill the block group with garbage if sanity checking is on */
- IF_DEBUG(sanity,memset(p->start, 0xaa, p->blocks * BLOCK_SIZE));
+ IF_DEBUG(sanity,memset(p->start, 0xaa, (W_)p->blocks * BLOCK_SIZE));
if (p->blocks == 0) barf("freeGroup: block size is zero");
low_mblocks = 1 + (blocks - BLOCKS_PER_MBLOCK) / (MBLOCK_SIZE / BLOCK_SIZE);
high_mblocks = (bd->blocks - blocks) / (MBLOCK_SIZE / BLOCK_SIZE);
- new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + low_mblocks * MBLOCK_SIZE_W);
+ new_mblock = (void *) ((P_)MBLOCK_ROUND_DOWN(bd) + (W_)low_mblocks * MBLOCK_SIZE_W);
initMBlock(new_mblock);
new_bd = FIRST_BDESCR(new_mblock);
new_bd->blocks = MBLOCK_GROUP_BLOCKS(high_mblocks);
}
/* -----------------------------------------------------------------------------
+ Stats / metrics
+ -------------------------------------------------------------------------- */
+
+nat
+countBlocks(bdescr *bd)
+{
+ nat n;
+ for (n=0; bd != NULL; bd=bd->link) {
+ n += bd->blocks;
+ }
+ return n;
+}
+
+// (*1) Just like countBlocks, except that we adjust the count for a
+// megablock group so that it doesn't include the extra few blocks
+// that would be taken up by block descriptors in the second and
+// subsequent megablock. This is so we can tally the count with the
+// number of blocks allocated in the system, for memInventory().
+nat
+countAllocdBlocks(bdescr *bd)
+{
+ nat n;
+ for (n=0; bd != NULL; bd=bd->link) {
+ n += bd->blocks;
+ // hack for megablock groups: see (*1) above
+ if (bd->blocks > BLOCKS_PER_MBLOCK) {
+ n -= (MBLOCK_SIZE / BLOCK_SIZE - BLOCKS_PER_MBLOCK)
+ * (bd->blocks/(MBLOCK_SIZE/BLOCK_SIZE));
+ }
+ }
+ return n;
+}
+
+void returnMemoryToOS(nat n /* megablocks */)
+{
+ static bdescr *bd;
+ nat size;
+
+ bd = free_mblock_list;
+ while ((n > 0) && (bd != NULL)) {
+ size = BLOCKS_TO_MBLOCKS(bd->blocks);
+ if (size > n) {
+ nat newSize = size - n;
+ char *freeAddr = MBLOCK_ROUND_DOWN(bd->start);
+ freeAddr += newSize * MBLOCK_SIZE;
+ bd->blocks = MBLOCK_GROUP_BLOCKS(newSize);
+ freeMBlocks(freeAddr, n);
+ n = 0;
+ }
+ else {
+ char *freeAddr = MBLOCK_ROUND_DOWN(bd->start);
+ n -= size;
+ bd = bd->link;
+ freeMBlocks(freeAddr, size);
+ }
+ }
+ free_mblock_list = bd;
+
+ osReleaseFreeMemory();
+
+ IF_DEBUG(gc,
+ if (n != 0) {
+ debugBelch("Wanted to free %d more MBlocks than are freeable\n",
+ n);
+ }
+ );
+}
+
+/* -----------------------------------------------------------------------------
Debugging
-------------------------------------------------------------------------- */
projects / ghc-hetmet.git / blobdiff