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7039089: G1: changeset for 7037276 broke heap verification, and related cleanups

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In G1 heap verification, we no longer scan perm to G1-collected heap refs as part of process_strong_roots() but rather in a separate explicit oop iteration over the perm gen. This preserves the original perm card-marks. Added a new assertion in younger_refs_iterate() to catch a simple subcase where the user may have forgotten a prior save_marks() call, as happened in the case of G1's attempt to iterate perm to G1 refs when verifying the heap before exit. The assert was deliberately weakened for ParNew+CMS and will be fixed for that combination in a future CR. Also made some (non-G1) cleanups related to code and comments obsoleted by the migration of Symbols to the native heap.

Reviewed-by: iveresov, jmasa, tonyp
This commit is contained in:
Y. Srinivas Ramakrishna 2011-04-26 21:17:24 -07:00
parent e3121a5a43
commit d86311b13c
8 changed files with 69 additions and 28 deletions
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13
hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.cpp
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@ -1963,10 +1963,21 @@ CompactibleFreeListSpace::gc_epilogue() {
// Iteration support, mostly delegated from a CMS generation
void CompactibleFreeListSpace::save_marks() {
// mark the "end" of the used space at the time of this call;
assert(Thread::current()->is_VM_thread(),
"Global variable should only be set when single-threaded");
// Mark the "end" of the used space at the time of this call;
// note, however, that promoted objects from this point
// on are tracked in the _promoInfo below.
set_saved_mark_word(unallocated_block());
#ifdef ASSERT
// Check the sanity of save_marks() etc.
MemRegion ur = used_region();
MemRegion urasm = used_region_at_save_marks();
assert(ur.contains(urasm),
err_msg(" Error at save_marks(): [" PTR_FORMAT "," PTR_FORMAT ")"
" should contain [" PTR_FORMAT "," PTR_FORMAT ")",
ur.start(), ur.end(), urasm.start(), urasm.end()));
#endif
// inform allocator that promotions should be tracked.
assert(_promoInfo.noPromotions(), "_promoInfo inconsistency");
_promoInfo.startTrackingPromotions();

5
hotspot/src/share/vm/gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.cpp
View file

@ -3189,10 +3189,9 @@ bool ConcurrentMarkSweepGeneration::is_too_full() const {
}
void CMSCollector::setup_cms_unloading_and_verification_state() {
const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC
const bool should_verify = VerifyBeforeGC || VerifyAfterGC || VerifyDuringGC
|| VerifyBeforeExit;
const int rso = SharedHeap::SO_Symbols | SharedHeap::SO_Strings
| SharedHeap::SO_CodeCache;
const int rso = SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
if (should_unload_classes()) { // Should unload classes this cycle
remove_root_scanning_option(rso); // Shrink the root set appropriately