37 static size_t bitmap_size(uint32_t size, size_t nsegments) {
38 // We need at least one bit per segment
39 return MAX2<size_t>(size, nsegments) * 2;
40 }
41
42 ZLiveMap::ZLiveMap(uint32_t size) :
43 _seqnum(0),
44 _live_objects(0),
45 _live_bytes(0),
46 _segment_live_bits(0),
47 _segment_claim_bits(0),
48 _bitmap(bitmap_size(size, nsegments)),
49 _segment_shift(exact_log2(segment_size())) {}
50
51 void ZLiveMap::reset(size_t index) {
52 const uint32_t seqnum_initializing = (uint32_t)-1;
53 bool contention = false;
54
55 // Multiple threads can enter here, make sure only one of them
56 // resets the marking information while the others busy wait.
57 for (uint32_t seqnum = _seqnum; seqnum != ZGlobalSeqNum; seqnum = _seqnum) {
58 if ((seqnum != seqnum_initializing) &&
59 (Atomic::cmpxchg(seqnum_initializing, &_seqnum, seqnum) == seqnum)) {
60 // Reset marking information
61 _live_bytes = 0;
62 _live_objects = 0;
63
64 // Clear segment claimed/live bits
65 segment_live_bits().clear();
66 segment_claim_bits().clear();
67
68 // Make sure the newly reset marking information is
69 // globally visible before updating the page seqnum.
70 OrderAccess::storestore();
71
72 // Update seqnum
73 assert(_seqnum == seqnum_initializing, "Invalid");
74 _seqnum = ZGlobalSeqNum;
75 break;
76 }
77
78 // Mark reset contention
79 if (!contention) {
80 // Count contention once
81 ZStatInc(ZCounterMarkSeqNumResetContention);
82 contention = true;
83
84 log_trace(gc)("Mark seqnum reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", bit: " SIZE_FORMAT,
85 ZThread::id(), ZThread::name(), p2i(this), index);
86 }
87 }
88 }
89
90 void ZLiveMap::reset_segment(BitMap::idx_t segment) {
91 bool contention = false;
92
93 if (!claim_segment(segment)) {
94 // Already claimed, wait for live bit to be set
96 // Busy wait. The loadload barrier is needed to make
97 // sure we re-read the live bit every time we loop.
98 OrderAccess::loadload();
99
100 // Mark reset contention
101 if (!contention) {
102 // Count contention once
103 ZStatInc(ZCounterMarkSegmentResetContention);
104 contention = true;
105
106 log_trace(gc)("Mark segment reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", segment: " SIZE_FORMAT,
107 ZThread::id(), ZThread::name(), p2i(this), segment);
108 }
109 }
110
111 // Segment is live
112 return;
113 }
114
115 // Segment claimed, clear it
116 const BitMap::idx_t start_index = segment_start(segment);
117 const BitMap::idx_t end_index = segment_end(segment);
118 if (segment_size() / BitsPerWord >= 32) {
119 _bitmap.clear_large_range(start_index, end_index);
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37 static size_t bitmap_size(uint32_t size, size_t nsegments) {
38 // We need at least one bit per segment
39 return MAX2<size_t>(size, nsegments) * 2;
40 }
41
42 ZLiveMap::ZLiveMap(uint32_t size) :
43 _seqnum(0),
44 _live_objects(0),
45 _live_bytes(0),
46 _segment_live_bits(0),
47 _segment_claim_bits(0),
48 _bitmap(bitmap_size(size, nsegments)),
49 _segment_shift(exact_log2(segment_size())) {}
50
51 void ZLiveMap::reset(size_t index) {
52 const uint32_t seqnum_initializing = (uint32_t)-1;
53 bool contention = false;
54
55 // Multiple threads can enter here, make sure only one of them
56 // resets the marking information while the others busy wait.
57 for (uint32_t seqnum = OrderAccess::load_acquire(&_seqnum);
58 seqnum != ZGlobalSeqNum;
59 seqnum = OrderAccess::load_acquire(&_seqnum)) {
60 if ((seqnum != seqnum_initializing) &&
61 (Atomic::cmpxchg(seqnum_initializing, &_seqnum, seqnum) == seqnum)) {
62 // Reset marking information
63 _live_bytes = 0;
64 _live_objects = 0;
65
66 // Clear segment claimed/live bits
67 segment_live_bits().clear();
68 segment_claim_bits().clear();
69
70 assert(_seqnum == seqnum_initializing, "Invalid");
71
72 // Make sure the newly reset marking information is ordered
73 // before the update of the page seqnum, such that when the
74 // up-to-date seqnum is load acquired, the bit maps will not
75 // contain stale information.
76 OrderAccess::release_store(&_seqnum, ZGlobalSeqNum);
77 break;
78 }
79
80 // Mark reset contention
81 if (!contention) {
82 // Count contention once
83 ZStatInc(ZCounterMarkSeqNumResetContention);
84 contention = true;
85
86 log_trace(gc)("Mark seqnum reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", bit: " SIZE_FORMAT,
87 ZThread::id(), ZThread::name(), p2i(this), index);
88 }
89 }
90 }
91
92 void ZLiveMap::reset_segment(BitMap::idx_t segment) {
93 bool contention = false;
94
95 if (!claim_segment(segment)) {
96 // Already claimed, wait for live bit to be set
98 // Mark reset contention
99 if (!contention) {
100 // Count contention once
101 ZStatInc(ZCounterMarkSegmentResetContention);
102 contention = true;
103
104 log_trace(gc)("Mark segment reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", segment: " SIZE_FORMAT,
105 ZThread::id(), ZThread::name(), p2i(this), segment);
106 }
107 }
108
109 // Segment is live
110 return;
111 }
112
113 // Segment claimed, clear it
114 const BitMap::idx_t start_index = segment_start(segment);
115 const BitMap::idx_t end_index = segment_end(segment);
116 if (segment_size() / BitsPerWord >= 32) {
117 _bitmap.clear_large_range(start_index, end_index);
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