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This commit is contained in:
Coleen Phillimore 2010-12-06 15:37:00 -05:00
commit faf320aede
10 changed files with 1060 additions and 403 deletions
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10
hotspot/src/share/vm/gc_implementation/g1/concurrentMark.cpp
View file

@ -1051,6 +1051,7 @@ public:
void work(int worker_i) {
assert(Thread::current()->is_ConcurrentGC_thread(),
"this should only be done by a conc GC thread");
ResourceMark rm;
double start_vtime = os::elapsedVTime();
@ -1888,6 +1889,9 @@ void ConcurrentMark::weakRefsWork(bool clear_all_soft_refs) {
G1CollectedHeap* g1h = G1CollectedHeap::heap();
ReferenceProcessor* rp = g1h->ref_processor();
// See the comment in G1CollectedHeap::ref_processing_init()
// about how reference processing currently works in G1.
// Process weak references.
rp->setup_policy(clear_all_soft_refs);
assert(_markStack.isEmpty(), "mark stack should be empty");
@ -2918,7 +2922,11 @@ public:
CMOopClosure(G1CollectedHeap* g1h,
ConcurrentMark* cm,
CMTask* task)
: _g1h(g1h), _cm(cm), _task(task) { }
: _g1h(g1h), _cm(cm), _task(task)
{
_ref_processor = g1h->ref_processor();
assert(_ref_processor != NULL, "should not be NULL");
}
};
void CMTask::setup_for_region(HeapRegion* hr) {

749
hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
View file

@ -58,10 +58,11 @@ size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
// INVARIANTS/NOTES
//
// All allocation activity covered by the G1CollectedHeap interface is
// serialized by acquiring the HeapLock. This happens in
// mem_allocate_work, which all such allocation functions call.
// (Note that this does not apply to TLAB allocation, which is not part
// of this interface: it is done by clients of this interface.)
// serialized by acquiring the HeapLock. This happens in mem_allocate
// and allocate_new_tlab, which are the "entry" points to the
// allocation code from the rest of the JVM. (Note that this does not
// apply to TLAB allocation, which is not part of this interface: it
// is done by clients of this interface.)
// Local to this file.
@ -536,15 +537,17 @@ HeapRegion* G1CollectedHeap::newAllocRegionWithExpansion(int purpose,
// If could fit into free regions w/o expansion, try.
// Otherwise, if can expand, do so.
// Otherwise, if using ex regions might help, try with ex given back.
HeapWord* G1CollectedHeap::humongousObjAllocate(size_t word_size) {
HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
assert_heap_locked_or_at_safepoint();
assert(regions_accounted_for(), "Region leakage!");
// We can't allocate H regions while cleanupComplete is running, since
// some of the regions we find to be empty might not yet be added to the
// unclean list. (If we're already at a safepoint, this call is
// unnecessary, not to mention wrong.)
if (!SafepointSynchronize::is_at_safepoint())
// We can't allocate humongous regions while cleanupComplete is
// running, since some of the regions we find to be empty might not
// yet be added to the unclean list. If we're already at a
// safepoint, this call is unnecessary, not to mention wrong.
if (!SafepointSynchronize::is_at_safepoint()) {
wait_for_cleanup_complete();
}
size_t num_regions =
round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
@ -598,106 +601,391 @@ HeapWord* G1CollectedHeap::humongousObjAllocate(size_t word_size) {
return res;
}
void
G1CollectedHeap::retire_cur_alloc_region(HeapRegion* cur_alloc_region) {
// The cleanup operation might update _summary_bytes_used
// concurrently with this method. So, right now, if we don't wait
// for it to complete, updates to _summary_bytes_used might get
// lost. This will be resolved in the near future when the operation
// of the free region list is revamped as part of CR 6977804.
wait_for_cleanup_complete();
retire_cur_alloc_region_common(cur_alloc_region);
assert(_cur_alloc_region == NULL, "post-condition");
}
// See the comment in the .hpp file about the locking protocol and
// assumptions of this method (and other related ones).
HeapWord*
G1CollectedHeap::attempt_allocation_slow(size_t word_size,
bool permit_collection_pause) {
HeapWord* res = NULL;
HeapRegion* allocated_young_region = NULL;
G1CollectedHeap::replace_cur_alloc_region_and_allocate(size_t word_size,
bool at_safepoint,
bool do_dirtying) {
assert_heap_locked_or_at_safepoint();
assert(_cur_alloc_region == NULL,
"replace_cur_alloc_region_and_allocate() should only be called "
"after retiring the previous current alloc region");
assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
"at_safepoint and is_at_safepoint() should be a tautology");
assert( SafepointSynchronize::is_at_safepoint() ||
Heap_lock->owned_by_self(), "pre condition of the call" );
if (isHumongous(word_size)) {
// Allocation of a humongous object can, in a sense, complete a
// partial region, if the previous alloc was also humongous, and
// caused the test below to succeed.
if (permit_collection_pause)
do_collection_pause_if_appropriate(word_size);
res = humongousObjAllocate(word_size);
assert(_cur_alloc_region == NULL
|| !_cur_alloc_region->isHumongous(),
"Prevent a regression of this bug.");
} else {
// We may have concurrent cleanup working at the time. Wait for it
// to complete. In the future we would probably want to make the
// concurrent cleanup truly concurrent by decoupling it from the
// allocation.
if (!SafepointSynchronize::is_at_safepoint())
if (!g1_policy()->is_young_list_full()) {
if (!at_safepoint) {
// The cleanup operation might update _summary_bytes_used
// concurrently with this method. So, right now, if we don't
// wait for it to complete, updates to _summary_bytes_used might
// get lost. This will be resolved in the near future when the
// operation of the free region list is revamped as part of
// CR 6977804. If we're already at a safepoint, this call is
// unnecessary, not to mention wrong.
wait_for_cleanup_complete();
// If we do a collection pause, this will be reset to a non-NULL
// value. If we don't, nulling here ensures that we allocate a new
// region below.
if (_cur_alloc_region != NULL) {
// We're finished with the _cur_alloc_region.
// As we're builing (at least the young portion) of the collection
// set incrementally we'll add the current allocation region to
// the collection set here.
if (_cur_alloc_region->is_young()) {
g1_policy()->add_region_to_incremental_cset_lhs(_cur_alloc_region);
}
_summary_bytes_used += _cur_alloc_region->used();
_cur_alloc_region = NULL;
}
assert(_cur_alloc_region == NULL, "Invariant.");
// Completion of a heap region is perhaps a good point at which to do
// a collection pause.
if (permit_collection_pause)
do_collection_pause_if_appropriate(word_size);
// Make sure we have an allocation region available.
if (_cur_alloc_region == NULL) {
if (!SafepointSynchronize::is_at_safepoint())
wait_for_cleanup_complete();
bool next_is_young = should_set_young_locked();
// If the next region is not young, make sure it's zero-filled.
_cur_alloc_region = newAllocRegion(word_size, !next_is_young);
if (_cur_alloc_region != NULL) {
_summary_bytes_used -= _cur_alloc_region->used();
if (next_is_young) {
set_region_short_lived_locked(_cur_alloc_region);
allocated_young_region = _cur_alloc_region;
}
}
}
assert(_cur_alloc_region == NULL || !_cur_alloc_region->isHumongous(),
"Prevent a regression of this bug.");
// Now retry the allocation.
if (_cur_alloc_region != NULL) {
if (allocated_young_region != NULL) {
// We need to ensure that the store to top does not
// float above the setting of the young type.
HeapRegion* new_cur_alloc_region = newAllocRegion(word_size,
false /* zero_filled */);
if (new_cur_alloc_region != NULL) {
assert(new_cur_alloc_region->is_empty(),
"the newly-allocated region should be empty, "
"as right now we only allocate new regions out of the free list");
g1_policy()->update_region_num(true /* next_is_young */);
_summary_bytes_used -= new_cur_alloc_region->used();
set_region_short_lived_locked(new_cur_alloc_region);
assert(!new_cur_alloc_region->isHumongous(),
"Catch a regression of this bug.");
// We need to ensure that the stores to _cur_alloc_region and,
// subsequently, to top do not float above the setting of the
// young type.
OrderAccess::storestore();
}
res = _cur_alloc_region->allocate(word_size);
}
}
// NOTE: fails frequently in PRT
assert(regions_accounted_for(), "Region leakage!");
// Now allocate out of the new current alloc region. We could
// have re-used allocate_from_cur_alloc_region() but its
// operation is slightly different to what we need here. First,
// allocate_from_cur_alloc_region() is only called outside a
// safepoint and will always unlock the Heap_lock if it returns
// a non-NULL result. Second, it assumes that the current alloc
// region is what's already assigned in _cur_alloc_region. What
// we want here is to actually do the allocation first before we
// assign the new region to _cur_alloc_region. This ordering is
// not currently important, but it will be essential when we
// change the code to support CAS allocation in the future (see
// CR 6994297).
//
// This allocate method does BOT updates and we don't need them in
// the young generation. This will be fixed in the near future by
// CR 6994297.
HeapWord* result = new_cur_alloc_region->allocate(word_size);
assert(result != NULL, "we just allocate out of an empty region "
"so allocation should have been successful");
assert(is_in(result), "result should be in the heap");
if (res != NULL) {
if (!SafepointSynchronize::is_at_safepoint()) {
assert( permit_collection_pause, "invariant" );
assert( Heap_lock->owned_by_self(), "invariant" );
_cur_alloc_region = new_cur_alloc_region;
if (!at_safepoint) {
Heap_lock->unlock();
}
if (allocated_young_region != NULL) {
HeapRegion* hr = allocated_young_region;
HeapWord* bottom = hr->bottom();
HeapWord* end = hr->end();
MemRegion mr(bottom, end);
((CardTableModRefBS*)_g1h->barrier_set())->dirty(mr);
// do the dirtying, if necessary, after we release the Heap_lock
if (do_dirtying) {
dirty_young_block(result, word_size);
}
return result;
}
}
assert( SafepointSynchronize::is_at_safepoint() ||
(res == NULL && Heap_lock->owned_by_self()) ||
(res != NULL && !Heap_lock->owned_by_self()),
"post condition of the call" );
assert(_cur_alloc_region == NULL, "we failed to allocate a new current "
"alloc region, it should still be NULL");
assert_heap_locked_or_at_safepoint();
return NULL;
}
return res;
// See the comment in the .hpp file about the locking protocol and
// assumptions of this method (and other related ones).
HeapWord*
G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
assert_heap_locked_and_not_at_safepoint();
assert(!isHumongous(word_size), "attempt_allocation_slow() should not be "
"used for humongous allocations");
// We will loop while succeeded is false, which means that we tried
// to do a collection, but the VM op did not succeed. So, when we
// exit the loop, either one of the allocation attempts was
// successful, or we succeeded in doing the VM op but which was
// unable to allocate after the collection.
for (int try_count = 1; /* we'll return or break */; try_count += 1) {
bool succeeded = true;
{
// We may have concurrent cleanup working at the time. Wait for
// it to complete. In the future we would probably want to make
// the concurrent cleanup truly concurrent by decoupling it from
// the allocation. This will happen in the near future as part
// of CR 6977804 which will revamp the operation of the free
// region list. The fact that wait_for_cleanup_complete() will
// do a wait() means that we'll give up the Heap_lock. So, it's
// possible that when we exit wait_for_cleanup_complete() we
// might be able to allocate successfully (since somebody else
// might have done a collection meanwhile). So, we'll attempt to
// allocate again, just in case. When we make cleanup truly
// concurrent with allocation, we should remove this allocation
// attempt as it's redundant (we only reach here after an
// allocation attempt has been unsuccessful).
wait_for_cleanup_complete();
HeapWord* result = attempt_allocation(word_size);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
}
if (GC_locker::is_active_and_needs_gc()) {
// We are locked out of GC because of the GC locker. Right now,
// we'll just stall until the GC locker-induced GC
// completes. This will be fixed in the near future by extending
// the eden while waiting for the GC locker to schedule the GC
// (see CR 6994056).
// If this thread is not in a jni critical section, we stall
// the requestor until the critical section has cleared and
// GC allowed. When the critical section clears, a GC is
// initiated by the last thread exiting the critical section; so
// we retry the allocation sequence from the beginning of the loop,
// rather than causing more, now probably unnecessary, GC attempts.
JavaThread* jthr = JavaThread::current();
assert(jthr != NULL, "sanity");
if (!jthr->in_critical()) {
MutexUnlocker mul(Heap_lock);
GC_locker::stall_until_clear();
// We'll then fall off the end of the ("if GC locker active")
// if-statement and retry the allocation further down in the
// loop.
} else {
if (CheckJNICalls) {
fatal("Possible deadlock due to allocating while"
" in jni critical section");
}
return NULL;
}
} else {
// We are not locked out. So, let's try to do a GC. The VM op
// will retry the allocation before it completes.
// Read the GC count while holding the Heap_lock
unsigned int gc_count_before = SharedHeap::heap()->total_collections();
Heap_lock->unlock();
HeapWord* result =
do_collection_pause(word_size, gc_count_before, &succeeded);
assert_heap_not_locked();
if (result != NULL) {
assert(succeeded, "the VM op should have succeeded");
// Allocations that take place on VM operations do not do any
// card dirtying and we have to do it here.
dirty_young_block(result, word_size);
return result;
}
Heap_lock->lock();
}
assert_heap_locked();
// We can reach here when we were unsuccessful in doing a GC,
// because another thread beat us to it, or because we were locked
// out of GC due to the GC locker. In either case a new alloc
// region might be available so we will retry the allocation.
HeapWord* result = attempt_allocation(word_size);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
// So far our attempts to allocate failed. The only time we'll go
// around the loop and try again is if we tried to do a GC and the
// VM op that we tried to schedule was not successful because
// another thread beat us to it. If that happened it's possible
// that by the time we grabbed the Heap_lock again and tried to
// allocate other threads filled up the young generation, which
// means that the allocation attempt after the GC also failed. So,
// it's worth trying to schedule another GC pause.
if (succeeded) {
break;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("G1CollectedHeap::attempt_allocation_slow() "
"retries %d times", try_count);
}
}
assert_heap_locked();
return NULL;
}
// See the comment in the .hpp file about the locking protocol and
// assumptions of this method (and other related ones).
HeapWord*
G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
bool at_safepoint) {
// This is the method that will allocate a humongous object. All
// allocation paths that attempt to allocate a humongous object
// should eventually reach here. Currently, the only paths are from
// mem_allocate() and attempt_allocation_at_safepoint().
assert_heap_locked_or_at_safepoint();
assert(isHumongous(word_size), "attempt_allocation_humongous() "
"should only be used for humongous allocations");
assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
"at_safepoint and is_at_safepoint() should be a tautology");
HeapWord* result = NULL;
// We will loop while succeeded is false, which means that we tried
// to do a collection, but the VM op did not succeed. So, when we
// exit the loop, either one of the allocation attempts was
// successful, or we succeeded in doing the VM op but which was
// unable to allocate after the collection.
for (int try_count = 1; /* we'll return or break */; try_count += 1) {
bool succeeded = true;
// Given that humongous objects are not allocated in young
// regions, we'll first try to do the allocation without doing a
// collection hoping that there's enough space in the heap.
result = humongous_obj_allocate(word_size);
assert(_cur_alloc_region == NULL || !_cur_alloc_region->isHumongous(),
"catch a regression of this bug.");
if (result != NULL) {
if (!at_safepoint) {
// If we're not at a safepoint, unlock the Heap_lock.
Heap_lock->unlock();
}
return result;
}
// If we failed to allocate the humongous object, we should try to
// do a collection pause (if we're allowed) in case it reclaims
// enough space for the allocation to succeed after the pause.
if (!at_safepoint) {
// Read the GC count while holding the Heap_lock
unsigned int gc_count_before = SharedHeap::heap()->total_collections();
// If we're allowed to do a collection we're not at a
// safepoint, so it is safe to unlock the Heap_lock.
Heap_lock->unlock();
result = do_collection_pause(word_size, gc_count_before, &succeeded);
assert_heap_not_locked();
if (result != NULL) {
assert(succeeded, "the VM op should have succeeded");
return result;
}
// If we get here, the VM operation either did not succeed
// (i.e., another thread beat us to it) or it succeeded but
// failed to allocate the object.
// If we're allowed to do a collection we're not at a
// safepoint, so it is safe to lock the Heap_lock.
Heap_lock->lock();
}
assert(result == NULL, "otherwise we should have exited the loop earlier");
// So far our attempts to allocate failed. The only time we'll go
// around the loop and try again is if we tried to do a GC and the
// VM op that we tried to schedule was not successful because
// another thread beat us to it. That way it's possible that some
// space was freed up by the thread that successfully scheduled a
// GC. So it's worth trying to allocate again.
if (succeeded) {
break;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("G1CollectedHeap::attempt_allocation_humongous "
"retries %d times", try_count);
}
}
assert_heap_locked_or_at_safepoint();
return NULL;
}
HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
bool expect_null_cur_alloc_region) {
assert_at_safepoint();
assert(_cur_alloc_region == NULL || !expect_null_cur_alloc_region,
err_msg("the current alloc region was unexpectedly found "
"to be non-NULL, cur alloc region: "PTR_FORMAT" "
"expect_null_cur_alloc_region: %d word_size: "SIZE_FORMAT,
_cur_alloc_region, expect_null_cur_alloc_region, word_size));
if (!isHumongous(word_size)) {
if (!expect_null_cur_alloc_region) {
HeapRegion* cur_alloc_region = _cur_alloc_region;
if (cur_alloc_region != NULL) {
// This allocate method does BOT updates and we don't need them in
// the young generation. This will be fixed in the near future by
// CR 6994297.
HeapWord* result = cur_alloc_region->allocate(word_size);
if (result != NULL) {
assert(is_in(result), "result should be in the heap");
// We will not do any dirtying here. This is guaranteed to be
// called during a safepoint and the thread that scheduled the
// pause will do the dirtying if we return a non-NULL result.
return result;
}
retire_cur_alloc_region_common(cur_alloc_region);
}
}
assert(_cur_alloc_region == NULL,
"at this point we should have no cur alloc region");
return replace_cur_alloc_region_and_allocate(word_size,
true, /* at_safepoint */
false /* do_dirtying */);
} else {
return attempt_allocation_humongous(word_size,
true /* at_safepoint */);
}
ShouldNotReachHere();
}
HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
assert_heap_not_locked_and_not_at_safepoint();
assert(!isHumongous(word_size), "we do not allow TLABs of humongous size");
Heap_lock->lock();
// First attempt: try allocating out of the current alloc region or
// after replacing the current alloc region.
HeapWord* result = attempt_allocation(word_size);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
assert_heap_locked();
// Second attempt: go into the even slower path where we might
// try to schedule a collection.
result = attempt_allocation_slow(word_size);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
assert_heap_locked();
Heap_lock->unlock();
return NULL;
}
HeapWord*
@ -705,46 +993,82 @@ G1CollectedHeap::mem_allocate(size_t word_size,
bool is_noref,
bool is_tlab,
bool* gc_overhead_limit_was_exceeded) {
debug_only(check_for_valid_allocation_state());
assert(no_gc_in_progress(), "Allocation during gc not allowed");
HeapWord* result = NULL;
assert_heap_not_locked_and_not_at_safepoint();
assert(!is_tlab, "mem_allocate() this should not be called directly "
"to allocate TLABs");
// Loop until the allocation is satisified,
// or unsatisfied after GC.
for (int try_count = 1; /* return or throw */; try_count += 1) {
int gc_count_before;
for (int try_count = 1; /* we'll return */; try_count += 1) {
unsigned int gc_count_before;
{
Heap_lock->lock();
result = attempt_allocation(word_size);
if (!isHumongous(word_size)) {
// First attempt: try allocating out of the current alloc
// region or after replacing the current alloc region.
HeapWord* result = attempt_allocation(word_size);
if (result != NULL) {
// attempt_allocation should have unlocked the heap lock
assert(is_in(result), "result not in heap");
assert_heap_not_locked();
return result;
}
assert_heap_locked();
// Second attempt: go into the even slower path where we might
// try to schedule a collection.
result = attempt_allocation_slow(word_size);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
} else {
HeapWord* result = attempt_allocation_humongous(word_size,
false /* at_safepoint */);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
}
assert_heap_locked();
// Read the gc count while the heap lock is held.
gc_count_before = SharedHeap::heap()->total_collections();
// We cannot be at a safepoint, so it is safe to unlock the Heap_lock
Heap_lock->unlock();
}
// Create the garbage collection operation...
VM_G1CollectForAllocation op(word_size,
gc_count_before);
VM_G1CollectForAllocation op(gc_count_before, word_size);
// ...and get the VM thread to execute it.
VMThread::execute(&op);
if (op.prologue_succeeded()) {
result = op.result();
assert(result == NULL || is_in(result), "result not in heap");
assert_heap_not_locked();
if (op.prologue_succeeded() && op.pause_succeeded()) {
// If the operation was successful we'll return the result even
// if it is NULL. If the allocation attempt failed immediately
// after a Full GC, it's unlikely we'll be able to allocate now.
HeapWord* result = op.result();
if (result != NULL && !isHumongous(word_size)) {
// Allocations that take place on VM operations do not do any
// card dirtying and we have to do it here. We only have to do
// this for non-humongous allocations, though.
dirty_young_block(result, word_size);
}
return result;
} else {
assert(op.result() == NULL,
"the result should be NULL if the VM op did not succeed");
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("G1CollectedHeap::mem_allocate_work retries %d times",
try_count);
warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
}
}
ShouldNotReachHere();
}
void G1CollectedHeap::abandon_cur_alloc_region() {
@ -841,11 +1165,11 @@ public:
}
};
void G1CollectedHeap::do_collection(bool explicit_gc,
bool G1CollectedHeap::do_collection(bool explicit_gc,
bool clear_all_soft_refs,
size_t word_size) {
if (GC_locker::check_active_before_gc()) {
return; // GC is disabled (e.g. JNI GetXXXCritical operation)
return false;
}
ResourceMark rm;
@ -929,6 +1253,9 @@ void G1CollectedHeap::do_collection(bool explicit_gc,
g1_policy()->set_full_young_gcs(true);
}
// See the comment in G1CollectedHeap::ref_processing_init() about
// how reference processing currently works in G1.
// Temporarily make reference _discovery_ single threaded (non-MT).
ReferenceProcessorMTMutator rp_disc_ser(ref_processor(), false);
@ -1047,10 +1374,17 @@ void G1CollectedHeap::do_collection(bool explicit_gc,
if (PrintHeapAtGC) {
Universe::print_heap_after_gc();
}
return true;
}
void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
do_collection(true, /* explicit_gc */
// do_collection() will return whether it succeeded in performing
// the GC. Currently, there is no facility on the
// do_full_collection() API to notify the caller than the collection
// did not succeed (e.g., because it was locked out by the GC
// locker). So, right now, we'll ignore the return value.
bool dummy = do_collection(true, /* explicit_gc */
clear_all_soft_refs,
0 /* word_size */);
}
@ -1175,36 +1509,63 @@ resize_if_necessary_after_full_collection(size_t word_size) {
HeapWord*
G1CollectedHeap::satisfy_failed_allocation(size_t word_size) {
HeapWord* result = NULL;
G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
bool* succeeded) {
assert(SafepointSynchronize::is_at_safepoint(),
"satisfy_failed_allocation() should only be called at a safepoint");
assert(Thread::current()->is_VM_thread(),
"satisfy_failed_allocation() should only be called by the VM thread");
*succeeded = true;
// Let's attempt the allocation first.
HeapWord* result = attempt_allocation_at_safepoint(word_size,
false /* expect_null_cur_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
}
// In a G1 heap, we're supposed to keep allocation from failing by
// incremental pauses. Therefore, at least for now, we'll favor
// expansion over collection. (This might change in the future if we can
// do something smarter than full collection to satisfy a failed alloc.)
result = expand_and_allocate(word_size);
if (result != NULL) {
assert(is_in(result), "result not in heap");
assert(*succeeded, "sanity");
return result;
}
// OK, I guess we have to try collection.
do_collection(false, false, word_size);
result = attempt_allocation(word_size, /*permit_collection_pause*/false);
// Expansion didn't work, we'll try to do a Full GC.
bool gc_succeeded = do_collection(false, /* explicit_gc */
false, /* clear_all_soft_refs */
word_size);
if (!gc_succeeded) {
*succeeded = false;
return NULL;
}
// Retry the allocation
result = attempt_allocation_at_safepoint(word_size,
true /* expect_null_cur_alloc_region */);
if (result != NULL) {
assert(is_in(result), "result not in heap");
assert(*succeeded, "sanity");
return result;
}
// Try collecting soft references.
do_collection(false, true, word_size);
result = attempt_allocation(word_size, /*permit_collection_pause*/false);
// Then, try a Full GC that will collect all soft references.
gc_succeeded = do_collection(false, /* explicit_gc */
true, /* clear_all_soft_refs */
word_size);
if (!gc_succeeded) {
*succeeded = false;
return NULL;
}
// Retry the allocation once more
result = attempt_allocation_at_safepoint(word_size,
true /* expect_null_cur_alloc_region */);
if (result != NULL) {
assert(is_in(result), "result not in heap");
assert(*succeeded, "sanity");
return result;
}
@ -1215,6 +1576,7 @@ G1CollectedHeap::satisfy_failed_allocation(size_t word_size) {
// space available is large enough for the allocation, then a more
// complete compaction phase than we've tried so far might be
// appropriate.
assert(*succeeded, "sanity");
return NULL;
}
@ -1224,14 +1586,20 @@ G1CollectedHeap::satisfy_failed_allocation(size_t word_size) {
// allocated block, or else "NULL".
HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
assert(SafepointSynchronize::is_at_safepoint(),
"expand_and_allocate() should only be called at a safepoint");
assert(Thread::current()->is_VM_thread(),
"expand_and_allocate() should only be called by the VM thread");
size_t expand_bytes = word_size * HeapWordSize;
if (expand_bytes < MinHeapDeltaBytes) {
expand_bytes = MinHeapDeltaBytes;
}
expand(expand_bytes);
assert(regions_accounted_for(), "Region leakage!");
HeapWord* result = attempt_allocation(word_size, false /* permit_collection_pause */);
return result;
return attempt_allocation_at_safepoint(word_size,
false /* expect_null_cur_alloc_region */);
}
size_t G1CollectedHeap::free_region_if_totally_empty(HeapRegion* hr) {
@ -1649,6 +2017,24 @@ jint G1CollectedHeap::initialize() {
}
void G1CollectedHeap::ref_processing_init() {
// Reference processing in G1 currently works as follows:
//
// * There is only one reference processor instance that
// 'spans' the entire heap. It is created by the code
// below.
// * Reference discovery is not enabled during an incremental
// pause (see 6484982).
// * Discoverered refs are not enqueued nor are they processed
// during an incremental pause (see 6484982).
// * Reference discovery is enabled at initial marking.
// * Reference discovery is disabled and the discovered
// references processed etc during remarking.
// * Reference discovery is MT (see below).
// * Reference discovery requires a barrier (see below).
// * Reference processing is currently not MT (see 6608385).
// * A full GC enables (non-MT) reference discovery and
// processes any discovered references.
SharedHeap::ref_processing_init();
MemRegion mr = reserved_region();
_ref_processor = ReferenceProcessor::create_ref_processor(
@ -1842,20 +2228,24 @@ void G1CollectedHeap::collect(GCCause::Cause cause) {
unsigned int full_gc_count_before;
{
MutexLocker ml(Heap_lock);
// Don't want to do a GC until cleanup is completed. This
// limitation will be removed in the near future when the
// operation of the free region list is revamped as part of
// CR 6977804.
wait_for_cleanup_complete();
// Read the GC count while holding the Heap_lock
gc_count_before = SharedHeap::heap()->total_collections();
full_gc_count_before = SharedHeap::heap()->total_full_collections();
// Don't want to do a GC until cleanup is completed.
wait_for_cleanup_complete();
// We give up heap lock; VMThread::execute gets it back below
}
if (should_do_concurrent_full_gc(cause)) {
// Schedule an initial-mark evacuation pause that will start a
// concurrent cycle.
// concurrent cycle. We're setting word_size to 0 which means that
// we are not requesting a post-GC allocation.
VM_G1IncCollectionPause op(gc_count_before,
0, /* word_size */
true, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
cause);
@ -1864,8 +2254,10 @@ void G1CollectedHeap::collect(GCCause::Cause cause) {
if (cause == GCCause::_gc_locker
DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
// Schedule a standard evacuation pause.
// Schedule a standard evacuation pause. We're setting word_size
// to 0 which means that we are not requesting a post-GC allocation.
VM_G1IncCollectionPause op(gc_count_before,
0, /* word_size */
false, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
cause);
@ -2221,14 +2613,6 @@ size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
}
}
HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
assert(!isHumongous(word_size),
err_msg("a TLAB should not be of humongous size, "
"word_size = "SIZE_FORMAT, word_size));
bool dummy;
return G1CollectedHeap::mem_allocate(word_size, false, true, &dummy);
}
bool G1CollectedHeap::allocs_are_zero_filled() {
return false;
}
@ -2633,27 +3017,26 @@ void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
// always_do_update_barrier = true;
}
void G1CollectedHeap::do_collection_pause() {
assert(Heap_lock->owned_by_self(), "we assume we'reholding the Heap_lock");
// Read the GC count while holding the Heap_lock
// we need to do this _before_ wait_for_cleanup_complete(), to
// ensure that we do not give up the heap lock and potentially
// pick up the wrong count
unsigned int gc_count_before = SharedHeap::heap()->total_collections();
// Don't want to do a GC pause while cleanup is being completed!
wait_for_cleanup_complete();
HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
unsigned int gc_count_before,
bool* succeeded) {
assert_heap_not_locked_and_not_at_safepoint();
g1_policy()->record_stop_world_start();
{
MutexUnlocker mu(Heap_lock); // give up heap lock, execute gets it back
VM_G1IncCollectionPause op(gc_count_before,
word_size,
false, /* should_initiate_conc_mark */
g1_policy()->max_pause_time_ms(),
GCCause::_g1_inc_collection_pause);
VMThread::execute(&op);
}
HeapWord* result = op.result();
bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
assert(result == NULL || ret_succeeded,
"the result should be NULL if the VM did not succeed");
*succeeded = ret_succeeded;
assert_heap_not_locked();
return result;
}
void
@ -2797,10 +3180,10 @@ void G1CollectedHeap::reset_taskqueue_stats() {
}
#endif // TASKQUEUE_STATS
void
bool
G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
if (GC_locker::check_active_before_gc()) {
return; // GC is disabled (e.g. JNI GetXXXCritical operation)
return false;
}
if (PrintHeapAtGC) {
@ -2871,6 +3254,9 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
COMPILER2_PRESENT(DerivedPointerTable::clear());
// Please see comment in G1CollectedHeap::ref_processing_init()
// to see how reference processing currently works in G1.
//
// We want to turn off ref discovery, if necessary, and turn it back on
// on again later if we do. XXX Dubious: why is discovery disabled?
bool was_enabled = ref_processor()->discovery_enabled();
@ -3068,6 +3454,8 @@ G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
(total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
g1_rem_set()->print_summary_info();
}
return true;
}
size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
@ -3298,6 +3686,7 @@ void G1CollectedHeap::release_gc_alloc_regions(bool totally) {
// untag the GC alloc regions and tear down the GC alloc region
// list. It's desirable that no regions are tagged as GC alloc
// outside GCs.
forget_alloc_region_list();
// The current alloc regions contain objs that have survived
@ -3361,19 +3750,6 @@ void G1CollectedHeap::finalize_for_evac_failure() {
// *** Sequential G1 Evacuation
HeapWord* G1CollectedHeap::allocate_during_gc(GCAllocPurpose purpose, size_t word_size) {
HeapRegion* alloc_region = _gc_alloc_regions[purpose];
// let the caller handle alloc failure
if (alloc_region == NULL) return NULL;
assert(isHumongous(word_size) || !alloc_region->isHumongous(),
"Either the object is humongous or the region isn't");
HeapWord* block = alloc_region->allocate(word_size);
if (block == NULL) {
block = allocate_during_gc_slow(purpose, alloc_region, false, word_size);
}
return block;
}
class G1IsAliveClosure: public BoolObjectClosure {
G1CollectedHeap* _g1;
public:
@ -4316,6 +4692,10 @@ g1_process_strong_roots(bool collecting_perm_gen,
}
// Finish with the ref_processor roots.
if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
// We need to treat the discovered reference lists as roots and
// keep entries (which are added by the marking threads) on them
// live until they can be processed at the end of marking.
ref_processor()->weak_oops_do(scan_non_heap_roots);
ref_processor()->oops_do(scan_non_heap_roots);
}
g1_policy()->record_collection_pause_end_G1_strong_roots();
@ -4381,6 +4761,11 @@ void G1CollectedHeap::evacuate_collection_set() {
// on individual heap regions when we allocate from
// them in parallel, so this seems like the correct place for this.
retire_all_alloc_regions();
// Weak root processing.
// Note: when JSR 292 is enabled and code blobs can contain
// non-perm oops then we will need to process the code blobs
// here too.
{
G1IsAliveClosure is_alive(this);
G1KeepAliveClosure keep_alive(this);
@ -4625,12 +5010,6 @@ void G1CollectedHeap::cleanUpCardTable() {
#endif
}
void G1CollectedHeap::do_collection_pause_if_appropriate(size_t word_size) {
if (g1_policy()->should_do_collection_pause(word_size)) {
do_collection_pause();
}
}
void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
double young_time_ms = 0.0;
double non_young_time_ms = 0.0;
@ -4789,6 +5168,7 @@ void G1CollectedHeap::set_unclean_regions_coming_locked(bool b) {
}
void G1CollectedHeap::wait_for_cleanup_complete() {
assert_not_at_safepoint();
MutexLockerEx x(Cleanup_mon);
wait_for_cleanup_complete_locked();
}
@ -5093,13 +5473,6 @@ size_t G1CollectedHeap::count_free_regions_list() {
return n + m;
}
bool G1CollectedHeap::should_set_young_locked() {
assert(heap_lock_held_for_gc(),
"the heap lock should already be held by or for this thread");
return (g1_policy()->in_young_gc_mode() &&
g1_policy()->should_add_next_region_to_young_list());
}
void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
assert(heap_lock_held_for_gc(),
"the heap lock should already be held by or for this thread");

273
hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp
View file

@ -290,6 +290,63 @@ private:
// started is maintained in _total_full_collections in CollectedHeap.
volatile unsigned int _full_collections_completed;
// These are macros so that, if the assert fires, we get the correct
// line number, file, etc.
#define heap_locking_asserts_err_msg(__extra_message) \
err_msg("%s : Heap_lock %slocked, %sat a safepoint", \
(__extra_message), \
(!Heap_lock->owned_by_self()) ? "NOT " : "", \
(!SafepointSynchronize::is_at_safepoint()) ? "NOT " : "")
#define assert_heap_locked() \
do { \
assert(Heap_lock->owned_by_self(), \
heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
} while (0)
#define assert_heap_locked_or_at_safepoint() \
do { \
assert(Heap_lock->owned_by_self() || \
SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
"should be at a safepoint")); \
} while (0)
#define assert_heap_locked_and_not_at_safepoint() \
do { \
assert(Heap_lock->owned_by_self() && \
!SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
"should not be at a safepoint")); \
} while (0)
#define assert_heap_not_locked() \
do { \
assert(!Heap_lock->owned_by_self(), \
heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
} while (0)
#define assert_heap_not_locked_and_not_at_safepoint() \
do { \
assert(!Heap_lock->owned_by_self() && \
!SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
"should not be at a safepoint")); \
} while (0)
#define assert_at_safepoint() \
do { \
assert(SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should be at a safepoint")); \
} while (0)
#define assert_not_at_safepoint() \
do { \
assert(!SafepointSynchronize::is_at_safepoint(), \
heap_locking_asserts_err_msg("should not be at a safepoint")); \
} while (0)
protected:
// Returns "true" iff none of the gc alloc regions have any allocations
@ -329,31 +386,162 @@ protected:
// Attempt to allocate an object of the given (very large) "word_size".
// Returns "NULL" on failure.
virtual HeapWord* humongousObjAllocate(size_t word_size);
virtual HeapWord* humongous_obj_allocate(size_t word_size);
// If possible, allocate a block of the given word_size, else return "NULL".
// Returning NULL will trigger GC or heap expansion.
// These two methods have rather awkward pre- and
// post-conditions. If they are called outside a safepoint, then
// they assume that the caller is holding the heap lock. Upon return
// they release the heap lock, if they are returning a non-NULL
// value. attempt_allocation_slow() also dirties the cards of a
// newly-allocated young region after it releases the heap
// lock. This change in interface was the neatest way to achieve
// this card dirtying without affecting mem_allocate(), which is a
// more frequently called method. We tried two or three different
// approaches, but they were even more hacky.
HeapWord* attempt_allocation(size_t word_size,
bool permit_collection_pause = true);
// The following two methods, allocate_new_tlab() and
// mem_allocate(), are the two main entry points from the runtime
// into the G1's allocation routines. They have the following
// assumptions:
//
// * They should both be called outside safepoints.
//
// * They should both be called without holding the Heap_lock.
//
// * All allocation requests for new TLABs should go to
// allocate_new_tlab().
//
// * All non-TLAB allocation requests should go to mem_allocate()
// and mem_allocate() should never be called with is_tlab == true.
//
// * If the GC locker is active we currently stall until we can
// allocate a new young region. This will be changed in the
// near future (see CR 6994056).
//
// * If either call cannot satisfy the allocation request using the
// current allocating region, they will try to get a new one. If
// this fails, they will attempt to do an evacuation pause and
// retry the allocation.
//
// * If all allocation attempts fail, even after trying to schedule
// an evacuation pause, allocate_new_tlab() will return NULL,
// whereas mem_allocate() will attempt a heap expansion and/or
// schedule a Full GC.
//
// * We do not allow humongous-sized TLABs. So, allocate_new_tlab
// should never be called with word_size being humongous. All
// humongous allocation requests should go to mem_allocate() which
// will satisfy them with a special path.
HeapWord* attempt_allocation_slow(size_t word_size,
bool permit_collection_pause = true);
virtual HeapWord* allocate_new_tlab(size_t word_size);
virtual HeapWord* mem_allocate(size_t word_size,
bool is_noref,
bool is_tlab, /* expected to be false */
bool* gc_overhead_limit_was_exceeded);
// The following methods, allocate_from_cur_allocation_region(),
// attempt_allocation(), replace_cur_alloc_region_and_allocate(),
// attempt_allocation_slow(), and attempt_allocation_humongous()
// have very awkward pre- and post-conditions with respect to
// locking:
//
// If they are called outside a safepoint they assume the caller
// holds the Heap_lock when it calls them. However, on exit they
// will release the Heap_lock if they return a non-NULL result, but
// keep holding the Heap_lock if they return a NULL result. The
// reason for this is that we need to dirty the cards that span
// allocated blocks on young regions to avoid having to take the
// slow path of the write barrier (for performance reasons we don't
// update RSets for references whose source is a young region, so we
// don't need to look at dirty cards on young regions). But, doing
// this card dirtying while holding the Heap_lock can be a
// scalability bottleneck, especially given that some allocation
// requests might be of non-trivial size (and the larger the region
// size is, the fewer allocations requests will be considered
// humongous, as the humongous size limit is a fraction of the
// region size). So, when one of these calls succeeds in allocating
// a block it does the card dirtying after it releases the Heap_lock
// which is why it will return without holding it.
//
// The above assymetry is the reason why locking / unlocking is done
// explicitly (i.e., with Heap_lock->lock() and
// Heap_lock->unlocked()) instead of using MutexLocker and
// MutexUnlocker objects. The latter would ensure that the lock is
// unlocked / re-locked at every possible exit out of the basic
// block. However, we only want that action to happen in selected
// places.
//
// Further, if the above methods are called during a safepoint, then
// naturally there's no assumption about the Heap_lock being held or
// there's no attempt to unlock it. The parameter at_safepoint
// indicates whether the call is made during a safepoint or not (as
// an optimization, to avoid reading the global flag with
// SafepointSynchronize::is_at_safepoint()).
//
// The methods share these parameters:
//
// * word_size : the size of the allocation request in words
// * at_safepoint : whether the call is done at a safepoint; this
// also determines whether a GC is permitted
// (at_safepoint == false) or not (at_safepoint == true)
// * do_dirtying : whether the method should dirty the allocated
// block before returning
//
// They all return either the address of the block, if they
// successfully manage to allocate it, or NULL.
// It tries to satisfy an allocation request out of the current
// allocating region, which is passed as a parameter. It assumes
// that the caller has checked that the current allocating region is
// not NULL. Given that the caller has to check the current
// allocating region for at least NULL, it might as well pass it as
// the first parameter so that the method doesn't have to read it
// from the _cur_alloc_region field again.
inline HeapWord* allocate_from_cur_alloc_region(HeapRegion* cur_alloc_region,
size_t word_size);
// It attempts to allocate out of the current alloc region. If that
// fails, it retires the current alloc region (if there is one),
// tries to get a new one and retries the allocation.
inline HeapWord* attempt_allocation(size_t word_size);
// It assumes that the current alloc region has been retired and
// tries to allocate a new one. If it's successful, it performs
// the allocation out of the new current alloc region and updates
// _cur_alloc_region.
HeapWord* replace_cur_alloc_region_and_allocate(size_t word_size,
bool at_safepoint,
bool do_dirtying);
// The slow path when we are unable to allocate a new current alloc
// region to satisfy an allocation request (i.e., when
// attempt_allocation() fails). It will try to do an evacuation
// pause, which might stall due to the GC locker, and retry the
// allocation attempt when appropriate.
HeapWord* attempt_allocation_slow(size_t word_size);
// The method that tries to satisfy a humongous allocation
// request. If it cannot satisfy it it will try to do an evacuation
// pause to perhaps reclaim enough space to be able to satisfy the
// allocation request afterwards.
HeapWord* attempt_allocation_humongous(size_t word_size,
bool at_safepoint);
// It does the common work when we are retiring the current alloc region.
inline void retire_cur_alloc_region_common(HeapRegion* cur_alloc_region);
// It retires the current alloc region, which is passed as a
// parameter (since, typically, the caller is already holding on to
// it). It sets _cur_alloc_region to NULL.
void retire_cur_alloc_region(HeapRegion* cur_alloc_region);
// It attempts to do an allocation immediately before or after an
// evacuation pause and can only be called by the VM thread. It has
// slightly different assumptions that the ones before (i.e.,
// assumes that the current alloc region has been retired).
HeapWord* attempt_allocation_at_safepoint(size_t word_size,
bool expect_null_cur_alloc_region);
// It dirties the cards that cover the block so that so that the post
// write barrier never queues anything when updating objects on this
// block. It is assumed (and in fact we assert) that the block
// belongs to a young region.
inline void dirty_young_block(HeapWord* start, size_t word_size);
// Allocate blocks during garbage collection. Will ensure an
// allocation region, either by picking one or expanding the
// heap, and then allocate a block of the given size. The block
// may not be a humongous - it must fit into a single heap region.
HeapWord* allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
@ -371,11 +559,13 @@ protected:
// - if explicit_gc is true, the GC is for a System.gc() or a heap
// inspection request and should collect the entire heap
// - if clear_all_soft_refs is true, all soft references are cleared
// during the GC
// - if clear_all_soft_refs is true, all soft references should be
// cleared during the GC
// - if explicit_gc is false, word_size describes the allocation that
// the GC should attempt (at least) to satisfy
void do_collection(bool explicit_gc,
// - it returns false if it is unable to do the collection due to the
// GC locker being active, true otherwise
bool do_collection(bool explicit_gc,
bool clear_all_soft_refs,
size_t word_size);
@ -391,13 +581,13 @@ protected:
// Callback from VM_G1CollectForAllocation operation.
// This function does everything necessary/possible to satisfy a
// failed allocation request (including collection, expansion, etc.)
HeapWord* satisfy_failed_allocation(size_t word_size);
HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
// Attempting to expand the heap sufficiently
// to support an allocation of the given "word_size". If
// successful, perform the allocation and return the address of the
// allocated block, or else "NULL".
virtual HeapWord* expand_and_allocate(size_t word_size);
HeapWord* expand_and_allocate(size_t word_size);
public:
// Expand the garbage-first heap by at least the given size (in bytes!).
@ -478,21 +668,27 @@ protected:
void reset_taskqueue_stats();
#endif // TASKQUEUE_STATS
// Do an incremental collection: identify a collection set, and evacuate
// its live objects elsewhere.
virtual void do_collection_pause();
// Schedule the VM operation that will do an evacuation pause to
// satisfy an allocation request of word_size. *succeeded will
// return whether the VM operation was successful (it did do an
// evacuation pause) or not (another thread beat us to it or the GC
// locker was active). Given that we should not be holding the
// Heap_lock when we enter this method, we will pass the
// gc_count_before (i.e., total_collections()) as a parameter since
// it has to be read while holding the Heap_lock. Currently, both
// methods that call do_collection_pause() release the Heap_lock
// before the call, so it's easy to read gc_count_before just before.
HeapWord* do_collection_pause(size_t word_size,
unsigned int gc_count_before,
bool* succeeded);
// The guts of the incremental collection pause, executed by the vm
// thread.
virtual void do_collection_pause_at_safepoint(double target_pause_time_ms);
// thread. It returns false if it is unable to do the collection due
// to the GC locker being active, true otherwise
bool do_collection_pause_at_safepoint(double target_pause_time_ms);
// Actually do the work of evacuating the collection set.
virtual void evacuate_collection_set();
// If this is an appropriate right time, do a collection pause.
// The "word_size" argument, if non-zero, indicates the size of an
// allocation request that is prompting this query.
void do_collection_pause_if_appropriate(size_t word_size);
void evacuate_collection_set();
// The g1 remembered set of the heap.
G1RemSet* _g1_rem_set;
@ -762,11 +958,6 @@ public:
#endif // PRODUCT
// These virtual functions do the actual allocation.
virtual HeapWord* mem_allocate(size_t word_size,
bool is_noref,
bool is_tlab,
bool* gc_overhead_limit_was_exceeded);
// Some heaps may offer a contiguous region for shared non-blocking
// allocation, via inlined code (by exporting the address of the top and
// end fields defining the extent of the contiguous allocation region.)
@ -1046,7 +1237,6 @@ public:
virtual bool supports_tlab_allocation() const;
virtual size_t tlab_capacity(Thread* thr) const;
virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
virtual HeapWord* allocate_new_tlab(size_t word_size);
// Can a compiler initialize a new object without store barriers?
// This permission only extends from the creation of a new object
@ -1186,7 +1376,6 @@ public:
static G1CollectedHeap* heap();
void empty_young_list();
bool should_set_young_locked();
void set_region_short_lived_locked(HeapRegion* hr);
// add appropriate methods for any other surv rate groups
@ -1339,8 +1528,6 @@ public:
protected:
size_t _max_heap_capacity;
// debug_only(static void check_for_valid_allocation_state();)
public:
// Temporary: call to mark things unimplemented for the G1 heap (e.g.,
// MemoryService). In productization, we can make this assert false

130
hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.inline.hpp
View file

@ -27,6 +27,7 @@
#include "gc_implementation/g1/concurrentMark.hpp"
#include "gc_implementation/g1/g1CollectedHeap.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/heapRegionSeq.hpp"
#include "utilities/taskqueue.hpp"
@ -58,37 +59,114 @@ inline bool G1CollectedHeap::obj_in_cs(oop obj) {
return r != NULL && r->in_collection_set();
}
inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
bool permit_collection_pause) {
HeapWord* res = NULL;
// See the comment in the .hpp file about the locking protocol and
// assumptions of this method (and other related ones).
inline HeapWord*
G1CollectedHeap::allocate_from_cur_alloc_region(HeapRegion* cur_alloc_region,
size_t word_size) {
assert_heap_locked_and_not_at_safepoint();
assert(cur_alloc_region != NULL, "pre-condition of the method");
assert(cur_alloc_region == _cur_alloc_region, "pre-condition of the method");
assert(cur_alloc_region->is_young(),
"we only support young current alloc regions");
assert(!isHumongous(word_size), "allocate_from_cur_alloc_region() "
"should not be used for humongous allocations");
assert(!cur_alloc_region->isHumongous(), "Catch a regression of this bug.");
assert( SafepointSynchronize::is_at_safepoint() ||
Heap_lock->owned_by_self(), "pre-condition of the call" );
// All humongous allocation requests should go through the slow path in
// attempt_allocation_slow().
if (!isHumongous(word_size) && _cur_alloc_region != NULL) {
// If this allocation causes a region to become non empty,
// then we need to update our free_regions count.
if (_cur_alloc_region->is_empty()) {
res = _cur_alloc_region->allocate(word_size);
if (res != NULL)
_free_regions--;
} else {
res = _cur_alloc_region->allocate(word_size);
}
if (res != NULL) {
if (!SafepointSynchronize::is_at_safepoint()) {
assert( Heap_lock->owned_by_self(), "invariant" );
assert(!cur_alloc_region->is_empty(),
err_msg("region ["PTR_FORMAT","PTR_FORMAT"] should not be empty",
cur_alloc_region->bottom(), cur_alloc_region->end()));
// This allocate method does BOT updates and we don't need them in
// the young generation. This will be fixed in the near future by
// CR 6994297.
HeapWord* result = cur_alloc_region->allocate(word_size);
if (result != NULL) {
assert(is_in(result), "result should be in the heap");
Heap_lock->unlock();
// Do the dirtying after we release the Heap_lock.
dirty_young_block(result, word_size);
return result;
}
return res;
assert_heap_locked();
return NULL;
}
// See the comment in the .hpp file about the locking protocol and
// assumptions of this method (and other related ones).
inline HeapWord*
G1CollectedHeap::attempt_allocation(size_t word_size) {
assert_heap_locked_and_not_at_safepoint();
assert(!isHumongous(word_size), "attempt_allocation() should not be called "
"for humongous allocation requests");
HeapRegion* cur_alloc_region = _cur_alloc_region;
if (cur_alloc_region != NULL) {
HeapWord* result = allocate_from_cur_alloc_region(cur_alloc_region,
word_size);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
assert_heap_locked();
// Since we couldn't successfully allocate into it, retire the
// current alloc region.
retire_cur_alloc_region(cur_alloc_region);
}
// attempt_allocation_slow will also unlock the heap lock when appropriate.
return attempt_allocation_slow(word_size, permit_collection_pause);
// Try to get a new region and allocate out of it
HeapWord* result = replace_cur_alloc_region_and_allocate(word_size,
false, /* at safepoint */
true /* do_dirtying */);
if (result != NULL) {
assert_heap_not_locked();
return result;
}
assert_heap_locked();
return NULL;
}
inline void
G1CollectedHeap::retire_cur_alloc_region_common(HeapRegion* cur_alloc_region) {
assert_heap_locked_or_at_safepoint();
assert(cur_alloc_region != NULL && cur_alloc_region == _cur_alloc_region,
"pre-condition of the call");
assert(cur_alloc_region->is_young(),
"we only support young current alloc regions");
// The region is guaranteed to be young
g1_policy()->add_region_to_incremental_cset_lhs(cur_alloc_region);
_summary_bytes_used += cur_alloc_region->used();
_cur_alloc_region = NULL;
}
// It dirties the cards that cover the block so that so that the post
// write barrier never queues anything when updating objects on this
// block. It is assumed (and in fact we assert) that the block
// belongs to a young region.
inline void
G1CollectedHeap::dirty_young_block(HeapWord* start, size_t word_size) {
assert_heap_not_locked();
// Assign the containing region to containing_hr so that we don't
// have to keep calling heap_region_containing_raw() in the
// asserts below.
DEBUG_ONLY(HeapRegion* containing_hr = heap_region_containing_raw(start);)
assert(containing_hr != NULL && start != NULL && word_size > 0,
"pre-condition");
assert(containing_hr->is_in(start), "it should contain start");
assert(containing_hr->is_young(), "it should be young");
assert(!containing_hr->isHumongous(), "it should not be humongous");
HeapWord* end = start + word_size;
assert(containing_hr->is_in(end - 1), "it should also contain end - 1");
MemRegion mr(start, end);
((CardTableModRefBS*)_g1h->barrier_set())->dirty(mr);
}
inline RefToScanQueue* G1CollectedHeap::task_queue(int i) const {

67
hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp
View file

@ -458,8 +458,8 @@ void G1CollectorPolicy::calculate_young_list_min_length() {
double now_sec = os::elapsedTime();
double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
double alloc_rate_ms = predict_alloc_rate_ms();
int min_regions = (int) ceil(alloc_rate_ms * when_ms);
int current_region_num = (int) _g1->young_list()->length();
size_t min_regions = (size_t) ceil(alloc_rate_ms * when_ms);
size_t current_region_num = _g1->young_list()->length();
_young_list_min_length = min_regions + current_region_num;
}
}
@ -473,9 +473,12 @@ void G1CollectorPolicy::calculate_young_list_target_length() {
_young_list_target_length = _young_list_fixed_length;
else
_young_list_target_length = _young_list_fixed_length / 2;
_young_list_target_length = MAX2(_young_list_target_length, (size_t)1);
}
// Make sure we allow the application to allocate at least one
// region before we need to do a collection again.
size_t min_length = _g1->young_list()->length() + 1;
_young_list_target_length = MAX2(_young_list_target_length, min_length);
calculate_survivors_policy();
}
@ -568,7 +571,7 @@ void G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths) {
// we should have at least one region in the target young length
_young_list_target_length =
MAX2((size_t) 1, final_young_length + _recorded_survivor_regions);
final_young_length + _recorded_survivor_regions;
// let's keep an eye of how long we spend on this calculation
// right now, I assume that we'll print it when we need it; we
@ -617,8 +620,7 @@ void G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths) {
_young_list_min_length);
#endif // TRACE_CALC_YOUNG_LENGTH
// we'll do the pause as soon as possible by choosing the minimum
_young_list_target_length =
MAX2(_young_list_min_length, (size_t) 1);
_young_list_target_length = _young_list_min_length;
}
_rs_lengths_prediction = rs_lengths;
@ -801,7 +803,7 @@ void G1CollectorPolicy::record_full_collection_end() {
_survivor_surv_rate_group->reset();
calculate_young_list_min_length();
calculate_young_list_target_length();
}
}
void G1CollectorPolicy::record_before_bytes(size_t bytes) {
_bytes_in_to_space_before_gc += bytes;
@ -824,9 +826,9 @@ void G1CollectorPolicy::record_collection_pause_start(double start_time_sec,
gclog_or_tty->print(" (%s)", full_young_gcs() ? "young" : "partial");
}
assert(_g1->used_regions() == _g1->recalculate_used_regions(),
"sanity");
assert(_g1->used() == _g1->recalculate_used(), "sanity");
assert(_g1->used() == _g1->recalculate_used(),
err_msg("sanity, used: "SIZE_FORMAT" recalculate_used: "SIZE_FORMAT,
_g1->used(), _g1->recalculate_used()));
double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0;
_all_stop_world_times_ms->add(s_w_t_ms);
@ -2266,24 +2268,13 @@ void G1CollectorPolicy::print_yg_surv_rate_info() const {
#endif // PRODUCT
}
bool
G1CollectorPolicy::should_add_next_region_to_young_list() {
assert(in_young_gc_mode(), "should be in young GC mode");
bool ret;
size_t young_list_length = _g1->young_list()->length();
size_t young_list_max_length = _young_list_target_length;
if (G1FixedEdenSize) {
young_list_max_length -= _max_survivor_regions;
}
if (young_list_length < young_list_max_length) {
ret = true;
void
G1CollectorPolicy::update_region_num(bool young) {
if (young) {
++_region_num_young;
} else {
ret = false;
++_region_num_tenured;
}
return ret;
}
#ifndef PRODUCT
@ -2327,32 +2318,6 @@ void G1CollectorPolicy::calculate_survivors_policy()
}
}
bool
G1CollectorPolicy_BestRegionsFirst::should_do_collection_pause(size_t
word_size) {
assert(_g1->regions_accounted_for(), "Region leakage!");
double max_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
size_t young_list_length = _g1->young_list()->length();
size_t young_list_max_length = _young_list_target_length;
if (G1FixedEdenSize) {
young_list_max_length -= _max_survivor_regions;
}
bool reached_target_length = young_list_length >= young_list_max_length;
if (in_young_gc_mode()) {
if (reached_target_length) {
assert( young_list_length > 0 && _g1->young_list()->length() > 0,
"invariant" );
return true;
}
} else {
guarantee( false, "should not reach here" );
}
return false;
}
#ifndef PRODUCT
class HRSortIndexIsOKClosure: public HeapRegionClosure {
CollectionSetChooser* _chooser;

17
hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.hpp
View file

@ -993,11 +993,6 @@ public:
void record_before_bytes(size_t bytes);
void record_after_bytes(size_t bytes);
// Returns "true" if this is a good time to do a collection pause.
// The "word_size" argument, if non-zero, indicates the size of an
// allocation request that is prompting this query.
virtual bool should_do_collection_pause(size_t word_size) = 0;
// Choose a new collection set. Marks the chosen regions as being
// "in_collection_set", and links them together. The head and number of
// the collection set are available via access methods.
@ -1116,7 +1111,16 @@ public:
// do that for any other surv rate groups
}
bool should_add_next_region_to_young_list();
bool is_young_list_full() {
size_t young_list_length = _g1->young_list()->length();
size_t young_list_max_length = _young_list_target_length;
if (G1FixedEdenSize) {
young_list_max_length -= _max_survivor_regions;
}
return young_list_length >= young_list_max_length;
}
void update_region_num(bool young);
bool in_young_gc_mode() {
return _in_young_gc_mode;
@ -1270,7 +1274,6 @@ public:
_collectionSetChooser = new CollectionSetChooser();
}
void record_collection_pause_end();
bool should_do_collection_pause(size_t word_size);
// This is not needed any more, after the CSet choosing code was
// changed to use the pause prediction work. But let's leave the
// hook in just in case.

53
hotspot/src/share/vm/gc_implementation/g1/vm_operations_g1.cpp
View file

@ -27,13 +27,22 @@
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/vm_operations_g1.hpp"
#include "gc_implementation/shared/isGCActiveMark.hpp"
#include "gc_implementation/g1/vm_operations_g1.hpp"
#include "runtime/interfaceSupport.hpp"
VM_G1CollectForAllocation::VM_G1CollectForAllocation(
unsigned int gc_count_before,
size_t word_size)
: VM_G1OperationWithAllocRequest(gc_count_before, word_size) {
guarantee(word_size > 0, "an allocation should always be requested");
}
void VM_G1CollectForAllocation::doit() {
JvmtiGCForAllocationMarker jgcm;
G1CollectedHeap* g1h = G1CollectedHeap::heap();
_res = g1h->satisfy_failed_allocation(_size);
assert(g1h->is_in_or_null(_res), "result not in heap");
_result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);
assert(_result == NULL || _pause_succeeded,
"if we get back a result, the pause should have succeeded");
}
void VM_G1CollectFull::doit() {
@ -43,6 +52,25 @@ void VM_G1CollectFull::doit() {
g1h->do_full_collection(false /* clear_all_soft_refs */);
}
VM_G1IncCollectionPause::VM_G1IncCollectionPause(
unsigned int gc_count_before,
size_t word_size,
bool should_initiate_conc_mark,
double target_pause_time_ms,
GCCause::Cause gc_cause)
: VM_G1OperationWithAllocRequest(gc_count_before, word_size),
_should_initiate_conc_mark(should_initiate_conc_mark),
_target_pause_time_ms(target_pause_time_ms),
_full_collections_completed_before(0) {
guarantee(target_pause_time_ms > 0.0,
err_msg("target_pause_time_ms = %1.6lf should be positive",
target_pause_time_ms));
guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,
"we can only request an allocation if the GC cause is for "
"an incremental GC pause");
_gc_cause = gc_cause;
}
void VM_G1IncCollectionPause::doit() {
JvmtiGCForAllocationMarker jgcm;
G1CollectedHeap* g1h = G1CollectedHeap::heap();
@ -51,6 +79,18 @@ void VM_G1IncCollectionPause::doit() {
(_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)),
"only a GC locker or a System.gc() induced GC should start a cycle");
if (_word_size > 0) {
// An allocation has been requested. So, try to do that first.
_result = g1h->attempt_allocation_at_safepoint(_word_size,
false /* expect_null_cur_alloc_region */);
if (_result != NULL) {
// If we can successfully allocate before we actually do the
// pause then we will consider this pause successful.
_pause_succeeded = true;
return;
}
}
GCCauseSetter x(g1h, _gc_cause);
if (_should_initiate_conc_mark) {
// It's safer to read full_collections_completed() here, given
@ -63,7 +103,16 @@ void VM_G1IncCollectionPause::doit() {
// will do so if one is not already in progress.
bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle();
}
_pause_succeeded =
g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
if (_pause_succeeded && _word_size > 0) {
// An allocation had been requested.
_result = g1h->attempt_allocation_at_safepoint(_word_size,
true /* expect_null_cur_alloc_region */);
} else {
assert(_result == NULL, "invariant");
}
}
void VM_G1IncCollectionPause::doit_epilogue() {

62
hotspot/src/share/vm/gc_implementation/g1/vm_operations_g1.hpp
View file

@ -31,19 +31,33 @@
// VM_GC_Operation:
// - VM_CGC_Operation
// - VM_G1CollectFull
// - VM_G1OperationWithAllocRequest
// - VM_G1CollectForAllocation
// - VM_G1IncCollectionPause
// - VM_G1PopRegionCollectionPause
class VM_G1OperationWithAllocRequest: public VM_GC_Operation {
protected:
size_t _word_size;
HeapWord* _result;
bool _pause_succeeded;
public:
VM_G1OperationWithAllocRequest(unsigned int gc_count_before,
size_t word_size)
: VM_GC_Operation(gc_count_before),
_word_size(word_size), _result(NULL), _pause_succeeded(false) { }
HeapWord* result() { return _result; }
bool pause_succeeded() { return _pause_succeeded; }
};
class VM_G1CollectFull: public VM_GC_Operation {
public:
public:
VM_G1CollectFull(unsigned int gc_count_before,
unsigned int full_gc_count_before,
GCCause::Cause cause)
: VM_GC_Operation(gc_count_before, full_gc_count_before) {
_gc_cause = cause;
}
~VM_G1CollectFull() {}
virtual VMOp_Type type() const { return VMOp_G1CollectFull; }
virtual void doit();
virtual const char* name() const {
@ -51,45 +65,28 @@ class VM_G1CollectFull: public VM_GC_Operation {
}
};
class VM_G1CollectForAllocation: public VM_GC_Operation {
private:
HeapWord* _res;
size_t _size; // size of object to be allocated
public:
VM_G1CollectForAllocation(size_t size, int gc_count_before)
: VM_GC_Operation(gc_count_before) {
_size = size;
_res = NULL;
}
~VM_G1CollectForAllocation() {}
class VM_G1CollectForAllocation: public VM_G1OperationWithAllocRequest {
public:
VM_G1CollectForAllocation(unsigned int gc_count_before,
size_t word_size);
virtual VMOp_Type type() const { return VMOp_G1CollectForAllocation; }
virtual void doit();
virtual const char* name() const {
return "garbage-first collection to satisfy allocation";
}
HeapWord* result() { return _res; }
};
class VM_G1IncCollectionPause: public VM_GC_Operation {
class VM_G1IncCollectionPause: public VM_G1OperationWithAllocRequest {
private:
bool _should_initiate_conc_mark;
double _target_pause_time_ms;
unsigned int _full_collections_completed_before;
public:
VM_G1IncCollectionPause(unsigned int gc_count_before,
size_t word_size,
bool should_initiate_conc_mark,
double target_pause_time_ms,
GCCause::Cause cause)
: VM_GC_Operation(gc_count_before),
_full_collections_completed_before(0),
_should_initiate_conc_mark(should_initiate_conc_mark),
_target_pause_time_ms(target_pause_time_ms) {
guarantee(target_pause_time_ms > 0.0,
err_msg("target_pause_time_ms = %1.6lf should be positive",
target_pause_time_ms));
_gc_cause = cause;
}
GCCause::Cause gc_cause);
virtual VMOp_Type type() const { return VMOp_G1IncCollectionPause; }
virtual void doit();
virtual void doit_epilogue();
@ -103,14 +100,9 @@ public:
class VM_CGC_Operation: public VM_Operation {
VoidClosure* _cl;
const char* _printGCMessage;
public:
VM_CGC_Operation(VoidClosure* cl, const char *printGCMsg) :
_cl(cl),
_printGCMessage(printGCMsg)
{}
~VM_CGC_Operation() {}
public:
VM_CGC_Operation(VoidClosure* cl, const char *printGCMsg)
: _cl(cl), _printGCMessage(printGCMsg) { }
virtual VMOp_Type type() const { return VMOp_CGC_Operation; }
virtual void doit();
virtual bool doit_prologue();

33
hotspot/src/share/vm/memory/referenceProcessor.cpp
View file

@ -770,8 +770,7 @@ void ReferenceProcessor::abandon_partial_discovery() {
// loop over the lists
for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) {
if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) {
gclog_or_tty->print_cr(
"\nAbandoning %s discovered list",
gclog_or_tty->print_cr("\nAbandoning %s discovered list",
list_name(i));
}
abandon_partial_discovered_list(_discoveredSoftRefs[i]);
@ -1059,9 +1058,7 @@ inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt)
// During a multi-threaded discovery phase,
// each thread saves to its "own" list.
Thread* thr = Thread::current();
assert(thr->is_GC_task_thread(),
"Dubious cast from Thread* to WorkerThread*?");
id = ((WorkerThread*)thr)->id();
id = thr->as_Worker_thread()->id();
} else {
// single-threaded discovery, we save in round-robin
// fashion to each of the lists.
@ -1095,8 +1092,7 @@ inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt)
ShouldNotReachHere();
}
if (TraceReferenceGC && PrintGCDetails) {
gclog_or_tty->print_cr("Thread %d gets list " INTPTR_FORMAT,
id, list);
gclog_or_tty->print_cr("Thread %d gets list " INTPTR_FORMAT, id, list);
}
return list;
}
@ -1135,6 +1131,11 @@ ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list,
if (_discovered_list_needs_barrier) {
_bs->write_ref_field((void*)discovered_addr, current_head);
}
if (TraceReferenceGC) {
gclog_or_tty->print_cr("Enqueued reference (mt) (" INTPTR_FORMAT ": %s)",
obj, obj->blueprint()->internal_name());
}
} else {
// If retest was non NULL, another thread beat us to it:
// The reference has already been discovered...
@ -1239,8 +1240,8 @@ bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) {
// Check assumption that an object is not potentially
// discovered twice except by concurrent collectors that potentially
// trace the same Reference object twice.
assert(UseConcMarkSweepGC,
"Only possible with an incremental-update concurrent collector");
assert(UseConcMarkSweepGC || UseG1GC,
"Only possible with a concurrent marking collector");
return true;
}
}
@ -1293,26 +1294,14 @@ bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) {
}
list->set_head(obj);
list->inc_length(1);
}
// In the MT discovery case, it is currently possible to see
// the following message multiple times if several threads
// discover a reference about the same time. Only one will
// however have actually added it to the disocvered queue.
// One could let add_to_discovered_list_mt() return an
// indication for success in queueing (by 1 thread) or
// failure (by all other threads), but I decided the extra
// code was not worth the effort for something that is
// only used for debugging support.
if (TraceReferenceGC) {
oop referent = java_lang_ref_Reference::referent(obj);
if (PrintGCDetails) {
gclog_or_tty->print_cr("Enqueued reference (" INTPTR_FORMAT ": %s)",
obj, obj->blueprint()->internal_name());
}
assert(referent->is_oop(), "Enqueued a bad referent");
}
assert(obj->is_oop(), "Enqueued a bad reference");
assert(java_lang_ref_Reference::referent(obj)->is_oop(), "Enqueued a bad referent");
return true;
}

13
hotspot/src/share/vm/runtime/thread.hpp
View file

@ -78,6 +78,8 @@ class GCTaskQueue;
class ThreadClosure;
class IdealGraphPrinter;
class WorkerThread;
// Class hierarchy
// - Thread
// - NamedThread
@ -289,6 +291,10 @@ class Thread: public ThreadShadow {
virtual bool is_Watcher_thread() const { return false; }
virtual bool is_ConcurrentGC_thread() const { return false; }
virtual bool is_Named_thread() const { return false; }
virtual bool is_Worker_thread() const { return false; }
// Casts
virtual WorkerThread* as_Worker_thread() const { return NULL; }
virtual char* name() const { return (char*)"Unknown thread"; }
@ -629,6 +635,13 @@ private:
uint _id;
public:
WorkerThread() : _id(0) { }
virtual bool is_Worker_thread() const { return true; }
virtual WorkerThread* as_Worker_thread() const {
assert(is_Worker_thread(), "Dubious cast to WorkerThread*?");
return (WorkerThread*) this;
}
void set_id(uint work_id) { _id = work_id; }
uint id() const { return _id; }
};