void do_MemRegion(MemRegion mr) {
// We start at the high end of "mr", walking backwards
// while accumulating a contiguous dirty range of cards in
// [start_of_non_clean, end_of_non_clean) which we then
// process en masse.
HeapWord* end_of_non_clean = mr.end();
HeapWord* start_of_non_clean = end_of_non_clean;
jbyte* entry = _ct->byte_for(mr.last());
const jbyte* first_entry = _ct->byte_for(mr.start());
while (entry >= first_entry) {
HeapWord* cur = _ct->addr_for(entry);
if (!clear_card(entry)) {
// We hit a clean card; process any non-empty
// dirty range accumulated so far.
if (start_of_non_clean < end_of_non_clean) {
MemRegion mr2(start_of_non_clean, end_of_non_clean);
_dirty_card_closure->do_MemRegion(mr2);
}
// Reset the dirty window while continuing to
// look for the next dirty window to process.
end_of_non_clean = cur;
start_of_non_clean = end_of_non_clean;
}
// Open the left end of the window one card to the left.
start_of_non_clean = cur;
// Note that "entry" leads "start_of_non_clean" in
// its leftward excursion after this point
// in the loop and, when we hit the left end of "mr",
// will point off of the left end of the card-table
// for "mr".
entry--;
}
// If the first card of "mr" was dirty, we will have
// been left with a dirty window, co-initial with "mr",
// which we now process.
if (start_of_non_clean < end_of_non_clean) {
MemRegion mr2(start_of_non_clean, end_of_non_clean);
_dirty_card_closure->do_MemRegion(mr2);
}
}
void do_MemRegion(MemRegion mr) {
HeapWord* end_of_non_clean = mr.end();
HeapWord* start_of_non_clean = end_of_non_clean;
jbyte* entry = _ct->byte_for(mr.last());
HeapWord* cur = _ct->addr_for(entry);
while (mr.contains(cur)) {
jbyte entry_val = *entry;
if (!clear_card(entry)) {
if (start_of_non_clean < end_of_non_clean) {
MemRegion mr2(start_of_non_clean, end_of_non_clean);
_dirty_card_closure->do_MemRegion(mr2);
}
end_of_non_clean = cur;
start_of_non_clean = end_of_non_clean;
}
entry--;
start_of_non_clean = cur;
cur = _ct->addr_for(entry);
}
if (start_of_non_clean < end_of_non_clean) {
MemRegion mr2(start_of_non_clean, end_of_non_clean);
_dirty_card_closure->do_MemRegion(mr2);
}
}
void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
// Some collectors need to do special things whenever their dirty
// cards are processed. For instance, CMS must remember mutator updates
// (i.e. dirty cards) so as to re-scan mutated objects.
// Such work can be piggy-backed here on dirty card scanning, so as to make
// it slightly more efficient than doing a complete non-detructive pre-scan
// of the card table.
MemRegionClosure* pCl = _sp->preconsumptionDirtyCardClosure();
if (pCl != NULL) {
pCl->do_MemRegion(mr);
}
HeapWord* bottom = mr.start();
HeapWord* last = mr.last();
HeapWord* top = mr.end();
HeapWord* bottom_obj;
HeapWord* top_obj;
assert(_precision == CardTableModRefBS::ObjHeadPreciseArray ||
_precision == CardTableModRefBS::Precise,
"Only ones we deal with for now.");
assert(_precision != CardTableModRefBS::ObjHeadPreciseArray ||
_cl->idempotent() || _last_bottom == NULL ||
top <= _last_bottom,
"Not decreasing");
NOT_PRODUCT(_last_bottom = mr.start());
bottom_obj = _sp->block_start(bottom);
top_obj = _sp->block_start(last);
assert(bottom_obj <= bottom, "just checking");
assert(top_obj <= top, "just checking");
// Given what we think is the top of the memory region and
// the start of the object at the top, get the actual
// value of the top.
top = get_actual_top(top, top_obj);
// If the previous call did some part of this region, don't redo.
if (_precision == CardTableModRefBS::ObjHeadPreciseArray &&
_min_done != NULL &&
_min_done < top) {
top = _min_done;
}
// Top may have been reset, and in fact may be below bottom,
// e.g. the dirty card region is entirely in a now free object
// -- something that could happen with a concurrent sweeper.
bottom = MIN2(bottom, top);
mr = MemRegion(bottom, top);
assert(bottom <= top &&
(_precision != CardTableModRefBS::ObjHeadPreciseArray ||
_min_done == NULL ||
top <= _min_done),
"overlap!");
// Walk the region if it is not empty; otherwise there is nothing to do.
if (!mr.is_empty()) {
walk_mem_region(mr, bottom_obj, top);
}
// An idempotent closure might be applied in any order, so we don't
// record a _min_done for it.
if (!_cl->idempotent()) {
_min_done = bottom;
} else {
assert(_min_done == _last_explicit_min_done,
"Don't update _min_done for idempotent cl");
}
}