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7045330: G1: Simplify/fix the HeapRegionSeq class 7042285: G1: native memory leak during humongous object allocation 6804436: G1: heap region indices should be size_t Summary: A series of fixes and improvements to the HeapRegionSeq class: a) replace the _regions growable array with a standard C array, b) avoid de-allocating / re-allocating HeapRegion instances when the heap shrinks / grows (fix for 7042285), c) introduce fast method to map address to HeapRegion via a "biased" array pointer, d) embed the _hrs object in G1CollectedHeap, instead of pointing to it via an indirection, e) assume that all the regions added to the HeapRegionSeq instance are contiguous, f) replace int's with size_t's for indexes (and expand that to HeapRegion as part of 6804436), g) remove unnecessary / unused methods, h) rename a couple of fields (_alloc_search_start and _seq_bottom), i) fix iterate_from() not to always start from index 0 irrespective of the region passed to it, j) add a verification method to check the HeapRegionSeq assumptions, k) always call the wrappers for _hrs.iterate(), _hrs_length(), and _hrs.at() from G1CollectedHeap, not those methods directly, and l) unify the code that expands the sequence (by either re-using or creating a new HeapRegion) and make it robust wrt to a HeapRegion allocation failing. Reviewed-by: stefank, johnc, brutisso
author tonyp
date Fri, 10 Jun 2011 13:16:40 -0400
parents 1216415d8e35
children 4f93f0d00802
comparison
equal deleted inserted replaced
3765:ae5b2f1dcf12 3766:c3f1170908be
23 */ 23 */
24 24
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP 25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
27 27
28 #include "gc_implementation/g1/heapRegion.hpp"
29 #include "utilities/growableArray.hpp"
30
31 class HeapRegion; 28 class HeapRegion;
32 class HeapRegionClosure; 29 class HeapRegionClosure;
30 class FreeRegionList;
31
32 #define G1_NULL_HRS_INDEX ((size_t) -1)
33
34 // This class keeps track of the region metadata (i.e., HeapRegion
35 // instances). They are kept in the _regions array in address
36 // order. A region's index in the array corresponds to its index in
37 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is
38 // the one after it, etc.). Two regions that are consecutive in the
39 // array should also be adjacent in the address space (i.e.,
40 // region(i).end() == region(i+1).bottom().
41 //
42 // We create a HeapRegion when we commit the region's address space
43 // for the first time. When we uncommit the address space of a
44 // region we retain the HeapRegion to be able to re-use it in the
45 // future (in case we recommit it).
46 //
47 // We keep track of three lengths:
48 //
49 // * _length (returned by length()) is the number of currently
50 // committed regions.
51 // * _allocated_length (not exposed outside this class) is the
52 // number of regions for which we have HeapRegions.
53 // * _max_length (returned by max_length()) is the maximum number of
54 // regions the heap can have.
55 //
56 // and maintain that: _length <= _allocated_length <= _max_length
33 57
34 class HeapRegionSeq: public CHeapObj { 58 class HeapRegionSeq: public CHeapObj {
35 59
36 // _regions is kept sorted by start address order, and no two regions are 60 // The array that holds the HeapRegions.
37 // overlapping. 61 HeapRegion** _regions;
38 GrowableArray<HeapRegion*> _regions;
39 62
40 // The index in "_regions" at which to start the next allocation search. 63 // Version of _regions biased to address 0
41 // (For efficiency only; private to obj_allocate after initialization.) 64 HeapRegion** _regions_biased;
42 int _alloc_search_start;
43 65
44 // Finds a contiguous set of empty regions of length num, starting 66 // The number of regions committed in the heap.
45 // from a given index. 67 size_t _length;
46 int find_contiguous_from(int from, size_t num);
47 68
48 // Currently, we're choosing collection sets in a round-robin fashion, 69 // The address of the first reserved word in the heap.
49 // starting here. 70 HeapWord* _heap_bottom;
50 int _next_rr_candidate;
51 71
52 // The bottom address of the bottom-most region, or else NULL if there 72 // The address of the last reserved word in the heap - 1.
53 // are no regions in the sequence. 73 HeapWord* _heap_end;
54 char* _seq_bottom; 74
75 // The log of the region byte size.
76 size_t _region_shift;
77
78 // A hint for which index to start searching from for humongous
79 // allocations.
80 size_t _next_search_index;
81
82 // The number of regions for which we have allocated HeapRegions for.
83 size_t _allocated_length;
84
85 // The maximum number of regions in the heap.
86 size_t _max_length;
87
88 // Find a contiguous set of empty regions of length num, starting
89 // from the given index.
90 size_t find_contiguous_from(size_t from, size_t num);
91
92 // Map a heap address to a biased region index. Assume that the
93 // address is valid.
94 inline size_t addr_to_index_biased(HeapWord* addr) const;
95
96 void increment_length(size_t* length) {
97 assert(*length < _max_length, "pre-condition");
98 *length += 1;
99 }
100
101 void decrement_length(size_t* length) {
102 assert(*length > 0, "pre-condition");
103 *length -= 1;
104 }
55 105
56 public: 106 public:
57 // Initializes "this" to the empty sequence of regions. 107 // Empty contructor, we'll initialize it with the initialize() method.
58 HeapRegionSeq(const size_t max_size); 108 HeapRegionSeq() { }
59 109
60 // Adds "hr" to "this" sequence. Requires "hr" not to overlap with 110 void initialize(HeapWord* bottom, HeapWord* end, size_t max_length);
61 // any region already in "this". (Will perform better if regions are
62 // inserted in ascending address order.)
63 void insert(HeapRegion* hr);
64 111
65 // Given a HeapRegion*, returns its index within _regions, 112 // Return the HeapRegion at the given index. Assume that the index
66 // or returns -1 if not found. 113 // is valid.
67 int find(HeapRegion* hr); 114 inline HeapRegion* at(size_t index) const;
68 115
69 // Requires the index to be valid, and return the region at the index. 116 // If addr is within the committed space return its corresponding
70 HeapRegion* at(size_t i) { return _regions.at((int)i); } 117 // HeapRegion, otherwise return NULL.
118 inline HeapRegion* addr_to_region(HeapWord* addr) const;
71 119
72 // Return the number of regions in the sequence. 120 // Return the HeapRegion that corresponds to the given
73 size_t length(); 121 // address. Assume the address is valid.
122 inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
74 123
75 // Returns the number of contiguous regions at the end of the sequence 124 // Return the number of regions that have been committed in the heap.
125 size_t length() const { return _length; }
126
127 // Return the maximum number of regions in the heap.
128 size_t max_length() const { return _max_length; }
129
130 // Expand the sequence to reflect that the heap has grown from
131 // old_end to new_end. Either create new HeapRegions, or re-use
132 // existing ones, and return them in the given list. Returns the
133 // memory region that covers the newly-created regions. If a
134 // HeapRegion allocation fails, the result memory region might be
135 // smaller than the desired one.
136 MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
137 FreeRegionList* list);
138
139 // Return the number of contiguous regions at the end of the sequence
76 // that are available for allocation. 140 // that are available for allocation.
77 size_t free_suffix(); 141 size_t free_suffix();
78 142
79 // Find a contiguous set of empty regions of length num and return 143 // Find a contiguous set of empty regions of length num and return
80 // the index of the first region or -1 if the search was unsuccessful. 144 // the index of the first region or G1_NULL_HRS_INDEX if the
81 int find_contiguous(size_t num); 145 // search was unsuccessful.
146 size_t find_contiguous(size_t num);
82 147
83 // Apply the "doHeapRegion" method of "blk" to all regions in "this", 148 // Apply blk->doHeapRegion() on all committed regions in address order,
84 // in address order, terminating the iteration early 149 // terminating the iteration early if doHeapRegion() returns true.
85 // if the "doHeapRegion" method returns "true". 150 void iterate(HeapRegionClosure* blk) const;
86 void iterate(HeapRegionClosure* blk);
87 151
88 // Apply the "doHeapRegion" method of "blk" to all regions in "this", 152 // As above, but start the iteration from hr and loop around. If hr
89 // starting at "r" (or first region, if "r" is NULL), in a circular 153 // is NULL, we start from the first region in the heap.
90 // manner, terminating the iteration early if the "doHeapRegion" method 154 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
91 // returns "true".
92 void iterate_from(HeapRegion* r, HeapRegionClosure* blk);
93 155
94 // As above, but start from a given index in the sequence 156 // Tag as uncommitted as many regions that are completely free as
95 // instead of a given heap region. 157 // possible, up to shrink_bytes, from the suffix of the committed
96 void iterate_from(int idx, HeapRegionClosure* blk); 158 // sequence. Return a MemRegion that corresponds to the address
159 // range of the uncommitted regions. Assume shrink_bytes is page and
160 // heap region aligned.
161 MemRegion shrink_by(size_t shrink_bytes, size_t* num_regions_deleted);
97 162
98 // Requires "shrink_bytes" to be a multiple of the page size and heap 163 // Do some sanity checking.
99 // region granularity. Deletes as many "rightmost" completely free heap 164 void verify_optional() PRODUCT_RETURN;
100 // regions from the sequence as comprise shrink_bytes bytes. Returns the
101 // MemRegion indicating the region those regions comprised, and sets
102 // "num_regions_deleted" to the number of regions deleted.
103 MemRegion shrink_by(size_t shrink_bytes, size_t& num_regions_deleted);
104
105 // If "addr" falls within a region in the sequence, return that region,
106 // or else NULL.
107 inline HeapRegion* addr_to_region(const void* addr);
108
109 void print();
110
111 // Prints out runs of empty regions.
112 void print_empty_runs();
113
114 }; 165 };
115 166
116 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP 167 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP