Fri, 10 Oct 2014 15:51:58 +0200
8059758: Footprint regressions with JDK-8038423
Summary: Changes in JDK-8038423 always initialize (zero out) virtual memory used for auxiliary data structures. This causes a footprint regression for G1 in startup benchmarks. This is because they do not touch that memory at all, so the operating system does not actually commit these pages. The fix is to, if the initialization value of the data structures matches the default value of just committed memory (=0), do not do anything.
Reviewed-by: jwilhelm, brutisso
1 /*
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25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/g1BiasedArray.hpp"
27 #include "memory/padded.inline.hpp"
29 // Allocate a new array, generic version.
30 address G1BiasedMappedArrayBase::create_new_base_array(size_t length, size_t elem_size) {
31 assert(length > 0, "just checking");
32 assert(elem_size > 0, "just checking");
33 return PaddedPrimitiveArray<u_char, mtGC>::create_unfreeable(length * elem_size);
34 }
36 #ifndef PRODUCT
37 void G1BiasedMappedArrayBase::verify_index(idx_t index) const {
38 guarantee(_base != NULL, "Array not initialized");
39 guarantee(index < length(), err_msg("Index out of bounds index: "SIZE_FORMAT" length: "SIZE_FORMAT, index, length()));
40 }
42 void G1BiasedMappedArrayBase::verify_biased_index(idx_t biased_index) const {
43 guarantee(_biased_base != NULL, "Array not initialized");
44 guarantee(biased_index >= bias() && biased_index < (bias() + length()),
45 err_msg("Biased index out of bounds, index: "SIZE_FORMAT" bias: "SIZE_FORMAT" length: "SIZE_FORMAT, biased_index, bias(), length()));
46 }
48 void G1BiasedMappedArrayBase::verify_biased_index_inclusive_end(idx_t biased_index) const {
49 guarantee(_biased_base != NULL, "Array not initialized");
50 guarantee(biased_index >= bias() && biased_index <= (bias() + length()),
51 err_msg("Biased index out of inclusive bounds, index: "SIZE_FORMAT" bias: "SIZE_FORMAT" length: "SIZE_FORMAT, biased_index, bias(), length()));
52 }
54 class TestMappedArray : public G1BiasedMappedArray<int> {
55 protected:
56 virtual int default_value() const { return 0xBAADBABE; }
57 public:
58 static void test_biasedarray() {
59 const size_t REGION_SIZE_IN_WORDS = 512;
60 const size_t NUM_REGIONS = 20;
61 HeapWord* fake_heap = (HeapWord*)LP64_ONLY(0xBAAA00000) NOT_LP64(0xBA000000); // Any value that is non-zero
63 TestMappedArray array;
64 array.initialize(fake_heap, fake_heap + REGION_SIZE_IN_WORDS * NUM_REGIONS,
65 REGION_SIZE_IN_WORDS * HeapWordSize);
66 // Check address calculation (bounds)
67 assert(array.bottom_address_mapped() == fake_heap,
68 err_msg("bottom mapped address should be " PTR_FORMAT ", but is " PTR_FORMAT, p2i(fake_heap), p2i(array.bottom_address_mapped())));
69 assert(array.end_address_mapped() == (fake_heap + REGION_SIZE_IN_WORDS * NUM_REGIONS), "must be");
71 int* bottom = array.address_mapped_to(fake_heap);
72 assert((void*)bottom == (void*) array.base(), "must be");
73 int* end = array.address_mapped_to(fake_heap + REGION_SIZE_IN_WORDS * NUM_REGIONS);
74 assert((void*)end == (void*)(array.base() + array.length()), "must be");
75 // The entire array should contain default value elements
76 for (int* current = bottom; current < end; current++) {
77 assert(*current == array.default_value(), "must be");
78 }
80 // Test setting values in the table
82 HeapWord* region_start_address = fake_heap + REGION_SIZE_IN_WORDS * (NUM_REGIONS / 2);
83 HeapWord* region_end_address = fake_heap + (REGION_SIZE_IN_WORDS * (NUM_REGIONS / 2) + REGION_SIZE_IN_WORDS - 1);
85 // Set/get by address tests: invert some value; first retrieve one
86 int actual_value = array.get_by_index(NUM_REGIONS / 2);
87 array.set_by_index(NUM_REGIONS / 2, ~actual_value);
88 // Get the same value by address, should correspond to the start of the "region"
89 int value = array.get_by_address(region_start_address);
90 assert(value == ~actual_value, "must be");
91 // Get the same value by address, at one HeapWord before the start
92 value = array.get_by_address(region_start_address - 1);
93 assert(value == array.default_value(), "must be");
94 // Get the same value by address, at the end of the "region"
95 value = array.get_by_address(region_end_address);
96 assert(value == ~actual_value, "must be");
97 // Make sure the next value maps to another index
98 value = array.get_by_address(region_end_address + 1);
99 assert(value == array.default_value(), "must be");
101 // Reset the value in the array
102 array.set_by_address(region_start_address + (region_end_address - region_start_address) / 2, actual_value);
104 // The entire array should have the default value again
105 for (int* current = bottom; current < end; current++) {
106 assert(*current == array.default_value(), "must be");
107 }
109 // Set/get by index tests: invert some value
110 idx_t index = NUM_REGIONS / 2;
111 actual_value = array.get_by_index(index);
112 array.set_by_index(index, ~actual_value);
114 value = array.get_by_index(index);
115 assert(value == ~actual_value, "must be");
117 value = array.get_by_index(index - 1);
118 assert(value == array.default_value(), "must be");
120 value = array.get_by_index(index + 1);
121 assert(value == array.default_value(), "must be");
123 array.set_by_index(0, 0);
124 value = array.get_by_index(0);
125 assert(value == 0, "must be");
127 array.set_by_index(array.length() - 1, 0);
128 value = array.get_by_index(array.length() - 1);
129 assert(value == 0, "must be");
131 array.set_by_index(index, 0);
133 // The array should have three zeros, and default values otherwise
134 size_t num_zeros = 0;
135 for (int* current = bottom; current < end; current++) {
136 assert(*current == array.default_value() || *current == 0, "must be");
137 if (*current == 0) {
138 num_zeros++;
139 }
140 }
141 assert(num_zeros == 3, "must be");
142 }
143 };
145 void TestG1BiasedArray_test() {
146 TestMappedArray::test_biasedarray();
147 }
149 #endif