1 /*
2 * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2017, 2022, Red Hat, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #ifndef SHARE_GC_EPSILON_EPSILONHEAP_HPP
27 #define SHARE_GC_EPSILON_EPSILONHEAP_HPP
28
29 #include "gc/epsilon/epsilonBarrierSet.hpp"
30 #include "gc/epsilon/epsilonMonitoringSupport.hpp"
31 #include "gc/shared/collectedHeap.hpp"
32 #include "gc/shared/space.hpp"
33 #include "memory/virtualspace.hpp"
34 #include "services/memoryManager.hpp"
35
36 class EpsilonHeap : public CollectedHeap {
37 friend class VMStructs;
38 private:
39 EpsilonMonitoringSupport* _monitoring_support;
40 MemoryPool* _pool;
41 GCMemoryManager _memory_manager;
42 ContiguousSpace* _space;
43 VirtualSpace _virtual_space;
44 size_t _max_tlab_size;
45 size_t _step_counter_update;
46 size_t _step_heap_print;
47 int64_t _decay_time_ns;
48 volatile size_t _last_counter_update;
49 volatile size_t _last_heap_print;
50
51 void print_tracing_info() const override;
52 void stop() override {};
53
54 public:
55 static EpsilonHeap* heap();
56
57 EpsilonHeap() :
58 _memory_manager("Epsilon Heap"),
59 _space(nullptr) {};
60
61 Name kind() const override {
62 return CollectedHeap::Epsilon;
63 }
64
65 const char* name() const override {
66 return "Epsilon";
67 }
68
69 jint initialize() override;
70 void initialize_serviceability() override;
71
72 GrowableArray<GCMemoryManager*> memory_managers() override;
73 GrowableArray<MemoryPool*> memory_pools() override;
74
75 size_t max_capacity() const override { return _virtual_space.reserved_size(); }
76 size_t capacity() const override { return _virtual_space.committed_size(); }
77 size_t used() const override { return _space->used(); }
78
79 bool is_in(const void* p) const override {
80 return _space->is_in(p);
81 }
82
83 bool requires_barriers(stackChunkOop obj) const override { return false; }
84
85 // Allocation
86 HeapWord* allocate_work(size_t size, bool verbose = true);
87 HeapWord* mem_allocate(size_t size) override;
88 HeapWord* allocate_new_tlab(size_t min_size,
89 size_t requested_size,
90 size_t* actual_size) override;
91
92 // TLAB allocation
93 size_t tlab_capacity(Thread* thr) const override { return capacity(); }
94 size_t tlab_used(Thread* thr) const override { return used(); }
95 size_t max_tlab_size() const override { return _max_tlab_size; }
96 size_t unsafe_max_tlab_alloc(Thread* thr) const override;
97
98 void collect(GCCause::Cause cause) override;
99 void do_full_collection(bool clear_all_soft_refs) override;
100
101 // Heap walking support
102 void object_iterate(ObjectClosure* cl) override;
103
104 // Object pinning support: every object is implicitly pinned
105 void pin_object(JavaThread* thread, oop obj) override { }
106 void unpin_object(JavaThread* thread, oop obj) override { }
107
108 // No support for block parsing.
109 HeapWord* block_start(const void* addr) const { return nullptr; }
110 bool block_is_obj(const HeapWord* addr) const { return false; }
111
112 // No GC threads
113 void gc_threads_do(ThreadClosure* tc) const override {}
114
115 // No nmethod handling
116 void register_nmethod(nmethod* nm) override {}
117 void unregister_nmethod(nmethod* nm) override {}
118 void verify_nmethod(nmethod* nm) override {}
119
120 // No heap verification
121 void prepare_for_verify() override {}
122 void verify(VerifyOption option) override {}
123
124 MemRegion reserved_region() const { return _reserved; }
125 bool is_in_reserved(const void* addr) const { return _reserved.contains(addr); }
126
127 // Support for loading objects from CDS archive into the heap
128 bool can_load_archived_objects() const override { return true; }
129 HeapWord* allocate_loaded_archive_space(size_t size) override;
130
131 void print_heap_on(outputStream* st) const override;
132 void print_gc_on(outputStream* st) const override {}
133 bool print_location(outputStream* st, void* addr) const override;
134
135 private:
136 void print_heap_info(size_t used) const;
137 void print_metaspace_info() const;
138
139 };
140
141 #endif // SHARE_GC_EPSILON_EPSILONHEAP_HPP