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8346920: Serial: Support allocation in old generation before GC #22899

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8346920: Serial: Support allocation in old generation before GC #22899

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ee6300d
s1-gc-time-ratio
albertnetymk Nov 27, 2024
453dcc3
Merge branch 'master' into s1-gc-time-ratio
albertnetymk Jan 6, 2025
52aa4ce
review
albertnetymk Jan 6, 2025
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1 change: 1 addition & 0 deletions src/hotspot/share/gc/serial/defNewGeneration.hpp
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Expand Up @@ -179,6 +179,7 @@ class DefNewGeneration: public Generation {
// Return true if the expansion was successful.
bool expand(size_t bytes);

STWGCTimer* gc_timer() const { return _gc_timer; }

// Iteration
void object_iterate(ObjectClosure* blk);
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26 changes: 23 additions & 3 deletions src/hotspot/share/gc/serial/serialHeap.cpp
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Expand Up @@ -329,9 +329,9 @@ HeapWord* SerialHeap::mem_allocate_work(size_t size,
{
MutexLocker ml(Heap_lock);
log_trace(gc, alloc)("SerialHeap::mem_allocate_work: attempting locked slow path allocation");
// Note that only large objects get a shot at being
// allocated in later generations.
bool first_only = !should_try_older_generation_allocation(size);

bool first_only = !should_try_older_generation_allocation(size)
&& is_long_enough_from_prev_gc_pause_end();
Comment on lines -332 to +334
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Is the first_only actually young_only? It means that the allocation is only attempted in young generation?

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That's true. I believe Serial used to support >2 generations, so some generic names are left as is. Fixing it requires updating in multiple places, such as the method name older_generation, arg in attempt_allocation, etc. How about we do that invasive but pure refactoring in its own PR?

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Yes, such refactoring should be finished in other issues.


result = attempt_allocation(size, is_tlab, first_only);
if (result != nullptr) {
Expand Down Expand Up @@ -634,6 +634,26 @@ void SerialHeap::scan_evacuated_objs(YoungGenScanClosure* young_cl,
guarantee(young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
}

bool SerialHeap::is_long_enough_from_prev_gc_pause_end() const {
Ticks young_gc_pause_end = _young_gen->gc_timer()->gc_end();
Ticks full_gc_pause_end = SerialFullGC::gc_timer()->gc_end();

Ticks prev_gc_pause_end;
Tickspan gc_pause;
if (full_gc_pause_end < young_gc_pause_end) {
// Previous is young-gc
prev_gc_pause_end = young_gc_pause_end;
gc_pause = young_gc_pause_end - _young_gen->gc_timer()->gc_start();
} else {
// Previous is full-gc
prev_gc_pause_end = full_gc_pause_end;
gc_pause = full_gc_pause_end - SerialFullGC::gc_timer()->gc_start();
}
Tickspan since_end_gc_pause = Ticks::now() - prev_gc_pause_end;

return since_end_gc_pause.seconds() * 100 >= gc_pause.seconds() * GCTimeRatio;
}

void SerialHeap::try_collect_at_safepoint(bool full) {
assert(SafepointSynchronize::is_at_safepoint(), "precondition");
if (GCLocker::check_active_before_gc()) {
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2 changes: 2 additions & 0 deletions src/hotspot/share/gc/serial/serialHeap.hpp
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Expand Up @@ -120,6 +120,8 @@ class SerialHeap : public CollectedHeap {

bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }

bool is_long_enough_from_prev_gc_pause_end() const;

// Performance Counter support
GCPolicyCounters* counters() { return _gc_policy_counters; }

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