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 = ZUtils::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 ZThreadLocalData::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
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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 = ZUtils::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 ZThreadLocalData::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
|