46   }
47 
48   // A max segment size of 64K was chosen because microbenchmarking
49   // suggested that it offered a good trade-off between allocation
50   // time and time-to-safepoint
51   const size_t segment_max = XUtils::bytes_to_words(64 * K);
52   const BasicType element_type = ArrayKlass::cast(_klass)->element_type();
53   const size_t header = arrayOopDesc::header_size(element_type);
54   const size_t payload_size = _word_size - header;
55 
56   if (payload_size <= segment_max) {
57     // To small to use segmented clearing
58     return ObjArrayAllocator::initialize(mem);
59   }
60 
61   // Segmented clearing
62 
63   // The array is going to be exposed before it has been completely
64   // cleared, therefore we can't expose the header at the end of this
65   // function. Instead explicitly initialize it according to our needs.
66   arrayOopDesc::set_mark(mem, markWord::prototype());
67   arrayOopDesc::release_set_klass(mem, _klass);
68   assert(_length >= 0, "length should be non-negative");
69   arrayOopDesc::set_length(mem, _length);
70 
71   // Keep the array alive across safepoints through an invisible
72   // root. Invisible roots are not visited by the heap itarator
73   // and the marking logic will not attempt to follow its elements.
74   // Relocation knows how to dodge iterating over such objects.
75   XThreadLocalData::set_invisible_root(_thread, (oop*)&mem);
76 
77   for (size_t processed = 0; processed < payload_size; processed += segment_max) {
78     // Calculate segment
79     HeapWord* const start = (HeapWord*)(mem + header + processed);
80     const size_t remaining = payload_size - processed;
81     const size_t segment_size = MIN2(remaining, segment_max);
82 
83     // Clear segment
84     Copy::zero_to_words(start, segment_size);
85 
86     // Safepoint

46   }
47 
48   // A max segment size of 64K was chosen because microbenchmarking
49   // suggested that it offered a good trade-off between allocation
50   // time and time-to-safepoint
51   const size_t segment_max = XUtils::bytes_to_words(64 * K);
52   const BasicType element_type = ArrayKlass::cast(_klass)->element_type();
53   const size_t header = arrayOopDesc::header_size(element_type);
54   const size_t payload_size = _word_size - header;
55 
56   if (payload_size <= segment_max) {
57     // To small to use segmented clearing
58     return ObjArrayAllocator::initialize(mem);
59   }
60 
61   // Segmented clearing
62 
63   // The array is going to be exposed before it has been completely
64   // cleared, therefore we can't expose the header at the end of this
65   // function. Instead explicitly initialize it according to our needs.
66   arrayOopDesc::set_mark(mem, Klass::default_prototype_header(_klass));
67   arrayOopDesc::release_set_klass(mem, _klass);
68   assert(_length >= 0, "length should be non-negative");
69   arrayOopDesc::set_length(mem, _length);
70 
71   // Keep the array alive across safepoints through an invisible
72   // root. Invisible roots are not visited by the heap itarator
73   // and the marking logic will not attempt to follow its elements.
74   // Relocation knows how to dodge iterating over such objects.
75   XThreadLocalData::set_invisible_root(_thread, (oop*)&mem);
76 
77   for (size_t processed = 0; processed < payload_size; processed += segment_max) {
78     // Calculate segment
79     HeapWord* const start = (HeapWord*)(mem + header + processed);
80     const size_t remaining = payload_size - processed;
81     const size_t segment_size = MIN2(remaining, segment_max);
82 
83     // Clear segment
84     Copy::zero_to_words(start, segment_size);
85 
86     // Safepoint