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7001033: assert(gch->gc_cause() == GCCause::_scavenge_alot || !gch->incremental_collection_failed())

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7002546: regression on SpecJbb2005 on 7b118 comparing to 7b117 on small heaps

Relaxed assertion checking related to incremental_collection_failed flag to allow for ExplicitGCInvokesConcurrent behaviour where we do not want a failing scavenge to bail to a stop-world collection. Parameterized incremental_collection_will_fail() so we can selectively use, or not use, as appropriate, the statistical prediction at specific use sites. This essentially reverts the scavenge bail-out logic to what it was prior to some recent changes that had inadvertently started using the statistical prediction which can be noisy in the presence of bursty loads. Added some associated verbose non-product debugging messages.

Reviewed-by: johnc, tonyp
This commit is contained in:
Y. Srinivas Ramakrishna 2010-12-07 21:55:53 -08:00
parent 4aaa89ea60
commit 544b475fc5
6 changed files with 54 additions and 23 deletions
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48
hotspot/src/share/vm/memory/defNewGeneration.cpp
View file

@ -483,16 +483,17 @@ void DefNewGeneration::space_iterate(SpaceClosure* blk,
// so we try to allocate the from-space, too.
HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
HeapWord* result = NULL;
if (PrintGC && Verbose) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
" will_fail: %s"
" heap_lock: %s"
" free: " SIZE_FORMAT,
size,
GenCollectedHeap::heap()->incremental_collection_will_fail() ? "true" : "false",
Heap_lock->is_locked() ? "locked" : "unlocked",
from()->free());
}
" will_fail: %s"
" heap_lock: %s"
" free: " SIZE_FORMAT,
size,
GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
"true" : "false",
Heap_lock->is_locked() ? "locked" : "unlocked",
from()->free());
}
if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
if (Heap_lock->owned_by_self() ||
(SafepointSynchronize::is_at_safepoint() &&
@ -534,6 +535,9 @@ void DefNewGeneration::collect(bool full,
// from this generation, pass on collection; let the next generation
// do it.
if (!collection_attempt_is_safe()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print(" :: Collection attempt not safe :: ");
}
gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
return;
}
@ -821,6 +825,9 @@ void DefNewGeneration::reset_scratch() {
bool DefNewGeneration::collection_attempt_is_safe() {
if (!to()->is_empty()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print(" :: to is not empty :: ");
}
return false;
}
if (_next_gen == NULL) {
@ -843,10 +850,18 @@ void DefNewGeneration::gc_epilogue(bool full) {
GenCollectedHeap* gch = GenCollectedHeap::heap();
if (full) {
DEBUG_ONLY(seen_incremental_collection_failed = false;)
if (!collection_attempt_is_safe()) {
if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
GCCause::to_string(gch->gc_cause()));
}
gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
set_should_allocate_from_space(); // we seem to be running out of space
} else {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
GCCause::to_string(gch->gc_cause()));
}
gch->clear_incremental_collection_failed(); // We just did a full collection
clear_should_allocate_from_space(); // if set
}
@ -860,11 +875,20 @@ void DefNewGeneration::gc_epilogue(bool full) {
// a full collection in between.
if (!seen_incremental_collection_failed &&
gch->incremental_collection_failed()) {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
GCCause::to_string(gch->gc_cause()));
}
seen_incremental_collection_failed = true;
} else if (seen_incremental_collection_failed) {
assert(gch->gc_cause() == GCCause::_scavenge_alot || !gch->incremental_collection_failed(),
if (Verbose && PrintGCDetails) {
gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
GCCause::to_string(gch->gc_cause()));
}
assert(gch->gc_cause() == GCCause::_scavenge_alot ||
(gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
!gch->incremental_collection_failed(),
"Twice in a row");
seen_incremental_collection_failed = false;
}
#endif // ASSERT