/* MVFFAddToFreeList -- Add given range to free list
*
* Updates MVFF counters for additional free space. Returns maximally
* coalesced range containing given range. Does not attempt to free
* segments (see MVFFFreeSegs).
*/
static Res MVFFAddToFreeList(Addr *baseIO, Addr *limitIO, MVFF mvff) {
Res res;
RangeStruct range, newRange;
AVER(baseIO != NULL);
AVER(limitIO != NULL);
AVERT(MVFF, mvff);
RangeInit(&range, *baseIO, *limitIO);
res = CBSInsert(&newRange, CBSOfMVFF(mvff), &range);
if (ResIsAllocFailure(res)) {
/* CBS ran out of memory for splay nodes: add range to emergency
* free list instead. */
res = FreelistInsert(&newRange, FreelistOfMVFF(mvff), &range);
}
if (res == ResOK) {
mvff->free += RangeSize(&range);
*baseIO = RangeBase(&newRange);
*limitIO = RangeLimit(&newRange);
}
return res;
}
static void shieldQueue(Arena arena, Seg seg)
{
Shield shield;
/* <design/trace/#fix.noaver> */
AVERT_CRITICAL(Arena, arena);
shield = ArenaShield(arena);
SHIELD_AVERT_CRITICAL(Seg, seg);
if (SegIsSynced(seg) || seg->queued)
return;
if (SegIsExposed(seg)) {
/* This can occur if the mutator isn't suspended, we expose a
segment, then raise the shield on it. In this case, the
mutator isn't allowed to see the segment, but we don't need to
queue it until its covered. */
shieldSuspend(arena);
return;
}
/* Allocate or extend the shield queue if necessary. */
if (shield->next >= shield->length) {
void *p;
Res res;
Count length;
AVER(shield->next == shield->length);
if (shield->length == 0)
length = ShieldQueueLENGTH;
else
length = shield->length * 2;
res = ControlAlloc(&p, arena, length * sizeof shield->queue[0]);
if (res != ResOK) {
AVER(ResIsAllocFailure(res));
/* Carry on with the existing queue. */
} else {
if (shield->length > 0) {
Size oldSize = shield->length * sizeof shield->queue[0];
AVER(shield->queue != NULL);
mps_lib_memcpy(p, shield->queue, oldSize);
ControlFree(arena, shield->queue, oldSize);
}
shield->queue = p;
shield->length = length;
}
}
/* Queue unavailable, so synchronize now. Or if the mutator is not
yet suspended and the code raises the shield on a covered
segment, protect it now, because that's probably better than
suspending the mutator. */
if (shield->length == 0 || !shield->suspended) {
shieldSync(shield, seg);
return;
}
AVER_CRITICAL(shield->limit <= shield->length);
AVER_CRITICAL(shield->next <= shield->limit);
/* If we failed to extend the shield queue array, degrade to an LRU
circular buffer. */
if (shield->next >= shield->length)
shield->next = 0;
AVER_CRITICAL(shield->next < shield->length);
AVER_CRITICAL(shield->length > 0);
/* If the limit is less than the length, then the queue array has
yet to be filled, and next is an uninitialized entry.
Otherwise it's the tail end from last time around, and needs to
be flushed. */
if (shield->limit >= shield->length) {
AVER_CRITICAL(shield->limit == shield->length);
shieldFlushEntry(shield, shield->next);
}
shield->queue[shield->next] = seg;
++shield->next;
seg->queued = TRUE;
if (shield->next >= shield->limit)
shield->limit = shield->next;
}
/* MVFFFreeSegs -- Free segments from given range
*
* Given a free range, attempts to find entire segments within
* it, and returns them to the arena, updating total size counter.
*
* This is usually called immediately after MVFFAddToFreeList.
* It is not combined with MVFFAddToFreeList because the latter
* is also called when new segments are added under MVFFAlloc.
*/
static void MVFFFreeSegs(MVFF mvff, Addr base, Addr limit)
{
Seg seg = NULL; /* suppress "may be used uninitialized" */
Arena arena;
Bool b;
Addr segLimit; /* limit of the current segment when iterating */
Addr segBase; /* base of the current segment when iterating */
Res res;
AVERT(MVFF, mvff);
AVER(base < limit);
/* Could profitably AVER that the given range is free, */
/* but the CBS doesn't provide that facility. */
if (AddrOffset(base, limit) < mvff->minSegSize)
return; /* not large enough for entire segments */
arena = PoolArena(MVFF2Pool(mvff));
b = SegOfAddr(&seg, arena, base);
AVER(b);
segBase = SegBase(seg);
segLimit = SegLimit(seg);
while(segLimit <= limit) { /* segment ends in range */
if (segBase >= base) { /* segment starts in range */
RangeStruct range, oldRange;
RangeInit(&range, segBase, segLimit);
res = CBSDelete(&oldRange, CBSOfMVFF(mvff), &range);
if (res == ResOK) {
mvff->free -= RangeSize(&range);
} else if (ResIsAllocFailure(res)) {
/* CBS ran out of memory for splay nodes, which must mean that
* there were fragments on both sides: see
* <design/cbs/#function.cbs.delete.fail>. Handle this by
* deleting the whole of oldRange (which requires no
* allocation) and re-inserting the fragments. */
RangeStruct oldRange2;
res = CBSDelete(&oldRange2, CBSOfMVFF(mvff), &oldRange);
AVER(res == ResOK);
AVER(RangesEqual(&oldRange2, &oldRange));
mvff->free -= RangeSize(&oldRange);
AVER(RangeBase(&oldRange) != segBase);
{
Addr leftBase = RangeBase(&oldRange);
Addr leftLimit = segBase;
res = MVFFAddToFreeList(&leftBase, &leftLimit, mvff);
}
AVER(RangeLimit(&oldRange) != segLimit);
{
Addr rightBase = segLimit;
Addr rightLimit = RangeLimit(&oldRange);
res = MVFFAddToFreeList(&rightBase, &rightLimit, mvff);
}
} else if (res == ResFAIL) {
/* Not found in the CBS: must be found in the Freelist. */
res = FreelistDelete(&oldRange, FreelistOfMVFF(mvff), &range);
AVER(res == ResOK);
mvff->free -= RangeSize(&range);
}
AVER(res == ResOK);
AVER(RangesNest(&oldRange, &range));
/* Can't free the segment earlier, because if it was on the
* Freelist rather than the CBS then it likely contains data
* that needs to be read in order to update the Freelist. */
SegFree(seg);
mvff->total -= RangeSize(&range);
}
/* Avoid calling SegNext if the next segment would fail */
/* the loop test, mainly because there might not be a */
/* next segment. */
if (segLimit == limit) /* segment ends at end of range */
break;
b = SegFindAboveAddr(&seg, arena, segBase);
AVER(b);
segBase = SegBase(seg);
segLimit = SegLimit(seg);
}
return;
}
