31 #include "oops/compressedOops.hpp"
32 #include "gc/shared/collectedHeap.hpp"
33 #include "runtime/arguments.hpp"
34 #include "runtime/globals.hpp"
35
36 // For UseCompressedOops.
37 address CompressedOops::_base = nullptr;
38 int CompressedOops::_shift = 0;
39 bool CompressedOops::_use_implicit_null_checks = true;
40 MemRegion CompressedOops::_heap_address_range;
41
42 // Choose the heap base address and oop encoding mode
43 // when compressed oops are used:
44 // Unscaled - Use 32-bits oops without encoding when
45 // NarrowOopHeapBaseMin + heap_size < 4Gb
46 // ZeroBased - Use zero based compressed oops with encoding when
47 // NarrowOopHeapBaseMin + heap_size < 32Gb
48 // HeapBased - Use compressed oops with heap base + encoding.
49 void CompressedOops::initialize(const ReservedHeapSpace& heap_space) {
50 #ifdef _LP64
51 // Subtract a page because something can get allocated at heap base.
52 // This also makes implicit null checking work, because the
53 // memory+1 page below heap_base needs to cause a signal.
54 // See needs_explicit_null_check.
55 // Only set the heap base for compressed oops because it indicates
56 // compressed oops for pstack code.
57 if ((uint64_t)heap_space.end() > UnscaledOopHeapMax) {
58 // Didn't reserve heap below 4Gb. Must shift.
59 set_shift(LogMinObjAlignmentInBytes);
60 }
61 if ((uint64_t)heap_space.end() <= OopEncodingHeapMax) {
62 // Did reserve heap below 32Gb. Can use base == 0;
63 set_base(nullptr);
64 } else {
65 set_base((address)heap_space.compressed_oop_base());
66 }
67
68 _heap_address_range = MemRegion((HeapWord*)heap_space.base(), (HeapWord*)heap_space.end());
69
70 LogTarget(Debug, gc, heap, coops) lt;
71 if (lt.is_enabled()) {
72 ResourceMark rm;
73 LogStream ls(lt);
74 print_mode(&ls);
75 }
76
77 // Tell tests in which mode we run.
78 Arguments::PropertyList_add(new SystemProperty("java.vm.compressedOopsMode",
79 mode_to_string(mode()),
80 false));
81
82 // base() is one page below the heap.
83 assert((intptr_t)base() <= ((intptr_t)_heap_address_range.start() - (intptr_t)os::vm_page_size()) ||
84 base() == nullptr, "invalid value");
85 assert(shift() == LogMinObjAlignmentInBytes ||
86 shift() == 0, "invalid value");
|
31 #include "oops/compressedOops.hpp"
32 #include "gc/shared/collectedHeap.hpp"
33 #include "runtime/arguments.hpp"
34 #include "runtime/globals.hpp"
35
36 // For UseCompressedOops.
37 address CompressedOops::_base = nullptr;
38 int CompressedOops::_shift = 0;
39 bool CompressedOops::_use_implicit_null_checks = true;
40 MemRegion CompressedOops::_heap_address_range;
41
42 // Choose the heap base address and oop encoding mode
43 // when compressed oops are used:
44 // Unscaled - Use 32-bits oops without encoding when
45 // NarrowOopHeapBaseMin + heap_size < 4Gb
46 // ZeroBased - Use zero based compressed oops with encoding when
47 // NarrowOopHeapBaseMin + heap_size < 32Gb
48 // HeapBased - Use compressed oops with heap base + encoding.
49 void CompressedOops::initialize(const ReservedHeapSpace& heap_space) {
50 #ifdef _LP64
51 if (UseCompatibleCompressedOops) {
52 set_shift(LogMinObjAlignmentInBytes);
53 set_base((address)heap_space.compressed_oop_base());
54 } else {
55 // Subtract a page because something can get allocated at heap base.
56 // This also makes implicit null checking work, because the
57 // memory+1 page below heap_base needs to cause a signal.
58 // See needs_explicit_null_check.
59 // Only set the heap base for compressed oops because it indicates
60 // compressed oops for pstack code.
61 if ((uint64_t)heap_space.end() > UnscaledOopHeapMax) {
62 // Didn't reserve heap below 4Gb. Must shift.
63 set_shift(LogMinObjAlignmentInBytes);
64 }
65 if ((uint64_t)heap_space.end() <= OopEncodingHeapMax) {
66 // Did reserve heap below 32Gb. Can use base == 0;
67 set_base(nullptr);
68 } else {
69 set_base((address)heap_space.compressed_oop_base());
70 }
71 }
72
73 _heap_address_range = MemRegion((HeapWord*)heap_space.base(), (HeapWord*)heap_space.end());
74
75 LogTarget(Debug, gc, heap, coops) lt;
76 if (lt.is_enabled()) {
77 ResourceMark rm;
78 LogStream ls(lt);
79 print_mode(&ls);
80 }
81
82 // Tell tests in which mode we run.
83 Arguments::PropertyList_add(new SystemProperty("java.vm.compressedOopsMode",
84 mode_to_string(mode()),
85 false));
86
87 // base() is one page below the heap.
88 assert((intptr_t)base() <= ((intptr_t)_heap_address_range.start() - (intptr_t)os::vm_page_size()) ||
89 base() == nullptr, "invalid value");
90 assert(shift() == LogMinObjAlignmentInBytes ||
91 shift() == 0, "invalid value");
|