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8007772: G1: assert(!hr->isHumongous() || mr.start() == hr->bottom()) failed: the start of HeapRegion and MemRegion should be consistent for humongous regions

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In do_marking_step(), we should always give up current region after scanning the object, if the region is humongous.

Reviewed-by: brutisso, jwilhelm, tamao
This commit is contained in:
John Cuthbertson 2013-02-11 15:24:48 -08:00
parent 4841066da4
commit 8316309c29
1 changed files with 26 additions and 17 deletions
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43
hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp
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@ -4062,27 +4062,36 @@ void CMTask::do_marking_step(double time_target_ms,
if (_cm->verbose_low()) {
gclog_or_tty->print_cr("[%u] we're scanning part "
"["PTR_FORMAT", "PTR_FORMAT") "
"of region "PTR_FORMAT,
_worker_id, _finger, _region_limit, _curr_region);
"of region "HR_FORMAT,
_worker_id, _finger, _region_limit,
HR_FORMAT_PARAMS(_curr_region));
}
HeapRegion* hr = _g1h->heap_region_containing(mr.start());
assert(!hr->isHumongous() || mr.start() == hr->bottom(),
"the start of HeapRegion and MemRegion should be consistent for humongous regions");
assert(!_curr_region->isHumongous() || mr.start() == _curr_region->bottom(),
"humongous regions should go around loop once only");
// The special case of the bitmap of a humongous region with its first
// bit NOT marked should be avoided from (wasteful) iterating.
// Note that the alternative case of the bitmap of a humongous region
// with its first bit marked is handled properly in the iterate() routine.
// Then, let's iterate over the bitmap of the part of the region that is
// left.
// Some special cases:
// If the memory region is empty, we can just give up the region.
// If the current region is humongous then we only need to check
// the bitmap for the bit associated with the start of the object,
// scan the object if it's live, and give up the region.
// Otherwise, let's iterate over the bitmap of the part of the region
// that is left.
// If the iteration is successful, give up the region.
// Also note that the case of the bitmap of a humongous region with its
// first bit NOT marked is considered "successful", leveraging the fact
// that the entire bitmap consists of all 0's in such case.
if (mr.is_empty() ||
(hr != NULL && hr->isHumongous() && !_nextMarkBitMap->isMarked(mr.start())) ||
_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
if (mr.is_empty()) {
giveup_current_region();
regular_clock_call();
} else if (_curr_region->isHumongous() && mr.start() == _curr_region->bottom()) {
if (_nextMarkBitMap->isMarked(mr.start())) {
// The object is marked - apply the closure
BitMap::idx_t offset = _nextMarkBitMap->heapWordToOffset(mr.start());
bitmap_closure.do_bit(offset);
}
// Even if this task aborted while scanning the humongous object
// we can (and should) give up the current region.
giveup_current_region();
regular_clock_call();
} else if (_nextMarkBitMap->iterate(&bitmap_closure, mr)) {
giveup_current_region();
regular_clock_call();
} else {