Thu, 20 Sep 2012 09:52:56 -0700
7190666: G1: assert(_unused == 0) failed: Inconsistency in PLAB stats
Summary: Reset the fields in ParGCAllocBuffer, that are used for accumulating values for the ResizePLAB sensors in PLABStats, to zero after flushing the values to the PLABStats fields. Flush PLABStats values only when retiring the final allocation buffers prior to disposing of a G1ParScanThreadState object, rather than when retiring every allocation buffer.
Reviewed-by: jwilhelm, jmasa, ysr
1 /*
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/shared/spaceDecorator.hpp"
27 #include "memory/space.inline.hpp"
28 #include "utilities/copy.hpp"
30 // Catch-all file for utility classes
32 #ifndef PRODUCT
34 // Returns true is the location q matches the mangling
35 // pattern.
36 bool SpaceMangler::is_mangled(HeapWord* q) {
37 // This test loses precision but is good enough
38 return badHeapWord == (max_juint & (uintptr_t) q->value());
39 }
42 void SpaceMangler::set_top_for_allocations(HeapWord* v) {
43 if (v < end()) {
44 assert(!CheckZapUnusedHeapArea || is_mangled(v),
45 "The high water mark is not mangled");
46 }
47 _top_for_allocations = v;
48 }
50 // Mangle only the unused space that has not previously
51 // been mangled and that has not been allocated since being
52 // mangled.
53 void SpaceMangler::mangle_unused_area() {
54 assert(ZapUnusedHeapArea, "Mangling should not be in use");
55 // Mangle between top and the high water mark. Safeguard
56 // against the space changing since top_for_allocations was
57 // set.
58 HeapWord* mangled_end = MIN2(top_for_allocations(), end());
59 if (top() < mangled_end) {
60 MemRegion mangle_mr(top(), mangled_end);
61 SpaceMangler::mangle_region(mangle_mr);
62 // Light weight check of mangling.
63 check_mangled_unused_area(end());
64 }
65 // Complete check of unused area which is functional when
66 // DEBUG_MANGLING is defined.
67 check_mangled_unused_area_complete();
68 }
70 // A complete mangle is expected in the
71 // exceptional case where top_for_allocations is not
72 // properly tracking the high water mark for mangling.
73 // This can be the case when to-space is being used for
74 // scratch space during a mark-sweep-compact. See
75 // contribute_scratch() and PSMarkSweep::allocate_stacks().
76 void SpaceMangler::mangle_unused_area_complete() {
77 assert(ZapUnusedHeapArea, "Mangling should not be in use");
78 MemRegion mangle_mr(top(), end());
79 SpaceMangler::mangle_region(mangle_mr);
80 }
82 // Simply mangle the MemRegion mr.
83 void SpaceMangler::mangle_region(MemRegion mr) {
84 assert(ZapUnusedHeapArea, "Mangling should not be in use");
85 #ifdef ASSERT
86 if(TraceZapUnusedHeapArea) {
87 gclog_or_tty->print("Mangling [0x%x to 0x%x)", mr.start(), mr.end());
88 }
89 Copy::fill_to_words(mr.start(), mr.word_size(), badHeapWord);
90 if(TraceZapUnusedHeapArea) {
91 gclog_or_tty->print_cr(" done");
92 }
93 #endif
94 }
96 // Check that top, top_for_allocations and the last
97 // word of the space are mangled. In a tight memory
98 // situation even this light weight mangling could
99 // cause paging by touching the end of the space.
100 void SpaceMangler::check_mangled_unused_area(HeapWord* limit) {
101 if (CheckZapUnusedHeapArea) {
102 // This method can be called while the spaces are
103 // being reshaped so skip the test if the end of the
104 // space is beyond the specified limit;
105 if (end() > limit) return;
107 assert(top() == end() ||
108 (is_mangled(top())), "Top not mangled");
109 assert((top_for_allocations() < top()) ||
110 (top_for_allocations() >= end()) ||
111 (is_mangled(top_for_allocations())),
112 "Older unused not mangled");
113 assert(top() == end() ||
114 (is_mangled(end() - 1)), "End not properly mangled");
115 // Only does checking when DEBUG_MANGLING is defined.
116 check_mangled_unused_area_complete();
117 }
118 }
120 #undef DEBUG_MANGLING
121 // This should only be used while debugging the mangling
122 // because of the high cost of checking the completeness.
123 void SpaceMangler::check_mangled_unused_area_complete() {
124 if (CheckZapUnusedHeapArea) {
125 assert(ZapUnusedHeapArea, "Not mangling unused area");
126 #ifdef DEBUG_MANGLING
127 HeapWord* q = top();
128 HeapWord* limit = end();
130 bool passed = true;
131 while (q < limit) {
132 if (!is_mangled(q)) {
133 passed = false;
134 break;
135 }
136 q++;
137 }
138 assert(passed, "Mangling is not complete");
139 #endif
140 }
141 }
142 #undef DEBUG_MANGLING
143 #endif // not PRODUCT