6688799: Second fix for Guarantee failure "Unexpected dirty card found"
Summary: Expand cardtable without committing over existing regions.
Reviewed-by: apetrusenko
--- a/hotspot/src/share/vm/memory/cardTableModRefBS.cpp Mon Jun 09 07:18:59 2008 -0700
+++ b/hotspot/src/share/vm/memory/cardTableModRefBS.cpp Tue Jun 10 07:26:42 2008 -0700
@@ -196,6 +196,8 @@
assert(_whole_heap.contains(new_region),
"attempt to cover area not in reserved area");
debug_only(verify_guard();)
+ // collided is true if the expansion would push into another committed region
+ debug_only(bool collided = false;)
int const ind = find_covering_region_by_base(new_region.start());
MemRegion const old_region = _covered[ind];
assert(old_region.start() == new_region.start(), "just checking");
@@ -211,12 +213,36 @@
}
// Align the end up to a page size (starts are already aligned).
jbyte* const new_end = byte_after(new_region.last());
- HeapWord* const new_end_aligned =
+ HeapWord* new_end_aligned =
(HeapWord*) align_size_up((uintptr_t)new_end, _page_size);
assert(new_end_aligned >= (HeapWord*) new_end,
"align up, but less");
+ int ri = 0;
+ for (ri = 0; ri < _cur_covered_regions; ri++) {
+ if (ri != ind) {
+ if (_committed[ri].contains(new_end_aligned)) {
+ assert((new_end_aligned >= _committed[ri].start()) &&
+ (_committed[ri].start() > _committed[ind].start()),
+ "New end of committed region is inconsistent");
+ new_end_aligned = _committed[ri].start();
+ assert(new_end_aligned > _committed[ind].start(),
+ "New end of committed region is before start");
+ debug_only(collided = true;)
+ // Should only collide with 1 region
+ break;
+ }
+ }
+ }
+#ifdef ASSERT
+ for (++ri; ri < _cur_covered_regions; ri++) {
+ assert(!_committed[ri].contains(new_end_aligned),
+ "New end of committed region is in a second committed region");
+ }
+#endif
// The guard page is always committed and should not be committed over.
- HeapWord* const new_end_for_commit = MIN2(new_end_aligned, _guard_region.start());
+ HeapWord* const new_end_for_commit = MIN2(new_end_aligned,
+ _guard_region.start());
+
if (new_end_for_commit > cur_committed.end()) {
// Must commit new pages.
MemRegion const new_committed =
@@ -239,9 +265,11 @@
if (!uncommit_region.is_empty()) {
if (!os::uncommit_memory((char*)uncommit_region.start(),
uncommit_region.byte_size())) {
- // Do better than this for Merlin
- vm_exit_out_of_memory(uncommit_region.byte_size(),
- "card table contraction");
+ assert(false, "Card table contraction failed");
+ // The call failed so don't change the end of the
+ // committed region. This is better than taking the
+ // VM down.
+ new_end_aligned = _committed[ind].end();
}
}
}
@@ -257,8 +285,25 @@
}
assert(index_for(new_region.last()) < (int) _guard_index,
"The guard card will be overwritten");
- jbyte* const end = byte_after(new_region.last());
+ // This line commented out cleans the newly expanded region and
+ // not the aligned up expanded region.
+ // jbyte* const end = byte_after(new_region.last());
+ jbyte* const end = (jbyte*) new_end_for_commit;
+ assert((end >= byte_after(new_region.last())) || collided,
+ "Expect to be beyond new region unless impacting another region");
// do nothing if we resized downward.
+#ifdef ASSERT
+ for (int ri = 0; ri < _cur_covered_regions; ri++) {
+ if (ri != ind) {
+ // The end of the new committed region should not
+ // be in any existing region unless it matches
+ // the start of the next region.
+ assert(!_committed[ri].contains(end) ||
+ (_committed[ri].start() == (HeapWord*) end),
+ "Overlapping committed regions");
+ }
+ }
+#endif
if (entry < end) {
memset(entry, clean_card, pointer_delta(end, entry, sizeof(jbyte)));
}