Mon, 02 Aug 2010 12:51:43 -0700
6814437: G1: remove the _new_refs array
Summary: The per-worker _new_refs array is used to hold references that point into the collection set. It is populated during RSet updating and subsequently processed. In the event of an evacuation failure it processed again to recreate the RSets of regions in the collection set. Remove the per-worker _new_refs array by processing the references directly. Use a DirtyCardQueue to hold the cards containing the references so that the RSets of regions in the collection set can be recreated when handling an evacuation failure.
Reviewed-by: iveresov, jmasa, tonyp
1 /*
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25 // Keeps track of the GC work and decides when it is OK to do GC work
26 // and for how long so that the MMU invariants are maintained.
28 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
30 // this is the "interface"
31 class G1MMUTracker: public CHeapObj {
32 protected:
33 double _time_slice;
34 double _max_gc_time; // this is per time slice
36 public:
37 G1MMUTracker(double time_slice, double max_gc_time);
39 virtual void add_pause(double start, double end, bool gc_thread) = 0;
40 virtual double longest_pause(double current_time) = 0;
41 virtual double when_sec(double current_time, double pause_time) = 0;
43 double max_gc_time() {
44 return _max_gc_time;
45 }
47 inline bool now_max_gc(double current_time) {
48 return when_sec(current_time, max_gc_time()) < 0.00001;
49 }
51 inline double when_max_gc_sec(double current_time) {
52 return when_sec(current_time, max_gc_time());
53 }
55 inline jlong when_max_gc_ms(double current_time) {
56 double when = when_max_gc_sec(current_time);
57 return (jlong) (when * 1000.0);
58 }
60 inline jlong when_ms(double current_time, double pause_time) {
61 double when = when_sec(current_time, pause_time);
62 return (jlong) (when * 1000.0);
63 }
64 };
66 class G1MMUTrackerQueueElem VALUE_OBJ_CLASS_SPEC {
67 private:
68 double _start_time;
69 double _end_time;
71 public:
72 inline double start_time() { return _start_time; }
73 inline double end_time() { return _end_time; }
74 inline double duration() { return _end_time - _start_time; }
76 G1MMUTrackerQueueElem() {
77 _start_time = 0.0;
78 _end_time = 0.0;
79 }
81 G1MMUTrackerQueueElem(double start_time, double end_time) {
82 _start_time = start_time;
83 _end_time = end_time;
84 }
85 };
87 // this is an implementation of the MMUTracker using a (fixed-size) queue
88 // that keeps track of all the recent pause times
89 class G1MMUTrackerQueue: public G1MMUTracker {
90 private:
91 enum PrivateConstants {
92 QueueLength = 64
93 };
95 // The array keeps track of all the pauses that fall within a time
96 // slice (the last time slice during which pauses took place).
97 // The data structure implemented is a circular queue.
98 // Head "points" to the most recent addition, tail to the oldest one.
99 // The array is of fixed size and I don't think we'll need more than
100 // two or three entries with the current behaviour of G1 pauses.
101 // If the array is full, an easy fix is to look for the pauses with
102 // the shortest gap between them and consolidate them.
103 // For now, we have taken the expedient alternative of forgetting
104 // the oldest entry in the event that +G1UseFixedWindowMMUTracker, thus
105 // potentially violating MMU specs for some time thereafter.
107 G1MMUTrackerQueueElem _array[QueueLength];
108 int _head_index;
109 int _tail_index;
110 int _no_entries;
112 inline int trim_index(int index) {
113 return (index + QueueLength) % QueueLength;
114 }
116 void remove_expired_entries(double current_time);
117 double calculate_gc_time(double current_time);
119 double longest_pause_internal(double current_time);
120 double when_internal(double current_time, double pause_time);
122 public:
123 G1MMUTrackerQueue(double time_slice, double max_gc_time);
125 virtual void add_pause(double start, double end, bool gc_thread);
127 virtual double longest_pause(double current_time);
128 virtual double when_sec(double current_time, double pause_time);
129 };