1 /*
2 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #ifndef SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP
26 #define SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP
27
28 #include "memory/allocation.hpp"
29 #include "oops/oop.hpp"
30 #include "runtime/handles.hpp"
31 #include "runtime/perfData.hpp"
32 #include "runtime/safepoint.hpp"
33
34 class nmethod;
35 class DepChange;
36
37 //
38 // nmethodBucket is used to record dependent nmethods for
39 // deoptimization. nmethod dependencies are actually <klass, method>
40 // pairs but we really only care about the klass part for purposes of
41 // finding nmethods which might need to be deoptimized. Instead of
42 // recording the method, a count of how many times a particular nmethod
43 // was recorded is kept. This ensures that any recording errors are
44 // noticed since an nmethod should be removed as many times are it's
45 // added.
46 //
47 class nmethodBucket: public CHeapObj<mtClass> {
48 friend class VMStructs;
49 private:
50 nmethod* _nmethod;
51 int _count;
52 nmethodBucket* _next;
53
54 public:
55 nmethodBucket(nmethod* nmethod, nmethodBucket* next) :
56 _nmethod(nmethod), _count(1), _next(next) {}
57
58 int count() { return _count; }
59 int increment() { _count += 1; return _count; }
60 int decrement();
61 nmethodBucket* next() { return _next; }
62 void set_next(nmethodBucket* b) { _next = b; }
63 nmethod* get_nmethod() { return _nmethod; }
64 };
65
66 //
67 // Utility class to manipulate nmethod dependency context.
68 // The context consists of nmethodBucket* (a head of a linked list)
69 // and a boolean flag (does the list contains stale entries). The structure is
70 // encoded as an intptr_t: lower bit is used for the flag. It is possible since
71 // nmethodBucket* is aligned - the structure is malloc'ed in C heap.
72 // Dependency context can be attached either to an InstanceKlass (_dep_context field)
73 // or CallSiteContext oop for call_site_target dependencies (see javaClasses.hpp).
74 // DependencyContext class operates on some location which holds a intptr_t value.
75 //
76 class DependencyContext : public StackObj {
77 friend class VMStructs;
78 friend class TestDependencyContext;
79 private:
80 enum TagBits { _has_stale_entries_bit = 1, _has_stale_entries_mask = 1 };
81
82 intptr_t* _dependency_context_addr;
83
84 void set_dependencies(nmethodBucket* b) {
85 assert((intptr_t(b) & _has_stale_entries_mask) == 0, "should be aligned");
86 if (has_stale_entries()) {
87 *_dependency_context_addr = intptr_t(b) | _has_stale_entries_mask;
88 } else {
89 *_dependency_context_addr = intptr_t(b);
90 }
91 }
92
93 void set_has_stale_entries(bool x) {
94 if (x) {
95 *_dependency_context_addr |= _has_stale_entries_mask;
96 } else {
97 *_dependency_context_addr &= ~_has_stale_entries_mask;
98 }
99 }
100
101 nmethodBucket* dependencies() {
102 intptr_t value = *_dependency_context_addr;
103 return (nmethodBucket*) (value & ~_has_stale_entries_mask);
104 }
105
106 bool has_stale_entries() const {
107 intptr_t value = *_dependency_context_addr;
108 return (value & _has_stale_entries_mask) != 0;
109 }
110
111 static PerfCounter* _perf_total_buckets_allocated_count;
112 static PerfCounter* _perf_total_buckets_deallocated_count;
113 static PerfCounter* _perf_total_buckets_stale_count;
114 static PerfCounter* _perf_total_buckets_stale_acc_count;
115
116 public:
117 #ifdef ASSERT
118 // Safepoints are forbidden during DC lifetime. GC can invalidate
119 // _dependency_context_addr if it relocates the holder
120 // (e.g. CallSiteContext Java object).
121 int _safepoint_counter;
122
123 DependencyContext(intptr_t* addr) : _dependency_context_addr(addr),
124 _safepoint_counter(SafepointSynchronize::_safepoint_counter) {}
125
126 ~DependencyContext() {
127 assert(_safepoint_counter == SafepointSynchronize::_safepoint_counter, "safepoint happened");
128 }
129 #else
130 DependencyContext(intptr_t* addr) : _dependency_context_addr(addr) {}
131 #endif // ASSERT
132
133 static const intptr_t EMPTY = 0; // dependencies = NULL, has_stale_entries = false
134
135 static void init();
136
137 int mark_dependent_nmethods(DepChange& changes);
138 void add_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
139 void remove_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
140 int remove_all_dependents();
141
142 void expunge_stale_entries();
143
144 #ifndef PRODUCT
145 void print_dependent_nmethods(bool verbose);
146 bool is_dependent_nmethod(nmethod* nm);
147 bool find_stale_entries();
148 #endif //PRODUCT
149 };
150 #endif // SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP