6944166: G1: explicit GCs are not always handled correctly
Summary: G1 was not handling explicit GCs correctly in many ways. It does now. See the CR for the list of improvements contained in this changeset.
Reviewed-by: iveresov, ysr, johnc
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// VM_operations for the G1 collector.
// VM_GC_Operation:
// - VM_CGC_Operation
// - VM_G1CollectFull
// - VM_G1CollectForAllocation
// - VM_G1IncCollectionPause
// - VM_G1PopRegionCollectionPause
class VM_G1CollectFull: public VM_GC_Operation {
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 {
return "full garbage-first collection";
}
};
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() {}
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 {
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,
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;
}
virtual VMOp_Type type() const { return VMOp_G1IncCollectionPause; }
virtual void doit();
virtual void doit_epilogue();
virtual const char* name() const {
return "garbage-first incremental collection pause";
}
};
// Concurrent GC stop-the-world operations such as initial and final mark;
// consider sharing these with CMS's counterparts.
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() {}
virtual VMOp_Type type() const { return VMOp_CGC_Operation; }
virtual void doit();
virtual bool doit_prologue();
virtual void doit_epilogue();
virtual const char* name() const {
return "concurrent gc";
}
};