1 /*
2 * Copyright (c) 2015, 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
33 class nmethod;
34 class DepChange;
35
36 //
37 // nmethodBucket is used to record dependent nmethods for
38 // deoptimization. nmethod dependencies are actually <klass, method>
39 // pairs but we really only care about the klass part for purposes of
40 // finding nmethods which might need to be deoptimized. Instead of
41 // recording the method, a count of how many times a particular nmethod
42 // was recorded is kept. This ensures that any recording errors are
43 // noticed since an nmethod should be removed as many times are it's
44 // added.
45 //
46 class nmethodBucket: public CHeapObj<mtClass> {
47 friend class VMStructs;
48 private:
49 nmethod* _nmethod;
50 int _count;
51 nmethodBucket* _next;
52
53 public:
54 nmethodBucket(nmethod* nmethod, nmethodBucket* next) :
55 _nmethod(nmethod), _next(next), _count(1) {}
56
57 int count() { return _count; }
58 int increment() { _count += 1; return _count; }
59 int decrement();
60 nmethodBucket* next() { return _next; }
61 void set_next(nmethodBucket* b) { _next = b; }
62 nmethod* get_nmethod() { return _nmethod; }
63 };
64
65 //
66 // Utility class to manipulate nmethod dependency context.
67 // The context consists of nmethodBucket* (a head of a linked list)
68 // and a boolean flag (does the list contains stale entries). The structure is
69 // encoded as an intptr_t: lower bit is used for the flag. It is possible since
70 // nmethodBucket* is aligned - the structure is malloc'ed in C heap.
71 // Dependency context can be attached either to an InstanceKlass (_dep_context field)
72 // or CallSiteContext oop for call_site_target dependencies (see javaClasses.hpp).
73 // DependencyContext class operates on some location which holds a intptr_t value.
74 //
75 class DependencyContext : public StackObj {
76 friend class VMStructs;
77 friend class TestDependencyContext;
78 private:
79 enum TagBits { _has_stale_entries_bit = 1, _has_stale_entries_mask = 1 };
80
81 intptr_t* _dependency_context_addr;
82
83 void set_dependencies(nmethodBucket* b) {
84 assert((intptr_t(b) & _has_stale_entries_mask) == 0, "should be aligned");
85 if (has_stale_entries()) {
86 *_dependency_context_addr = intptr_t(b) | _has_stale_entries_mask;
87 } else {
88 *_dependency_context_addr = intptr_t(b);
89 }
90 }
91
92 void set_has_stale_entries(bool x) {
93 if (x) {
94 *_dependency_context_addr |= _has_stale_entries_mask;
95 } else {
96 *_dependency_context_addr &= ~_has_stale_entries_mask;
97 }
98 }
99
100 nmethodBucket* dependencies() {
101 intptr_t value = *_dependency_context_addr;
102 return (nmethodBucket*) (value & ~_has_stale_entries_mask);
103 }
104
105 bool has_stale_entries() const {
106 intptr_t value = *_dependency_context_addr;
107 return (value & _has_stale_entries_mask) != 0;
108 }
109
110 static PerfCounter* _perf_total_buckets_allocated_count;
111 static PerfCounter* _perf_total_buckets_deallocated_count;
112 static PerfCounter* _perf_total_buckets_stale_count;
113 static PerfCounter* _perf_total_buckets_stale_acc_count;
114
115 public:
116 #ifdef ASSERT
117 // Verification for dependency contexts rooted at Java objects.
118 Handle _base; // non-NULL if dependency context resides in an oop (e.g. CallSite).
119 oop _base_oop;
120
121 DependencyContext(intptr_t* addr, Handle base = Handle())
122 : _dependency_context_addr(addr), _base(base)
123 {
124 _base_oop = _base();
125 }
126
127 ~DependencyContext() {
128 // Base oop relocation invalidates _dependency_context_addr.
129 assert(_base_oop == _base(), "base oop relocation is forbidden");
130 }
131 #else
132 DependencyContext(intptr_t* addr) : _dependency_context_addr(addr) {}
133 #endif // ASSERT
134
135 static const intptr_t EMPTY = 0; // dependencies = NULL, has_stale_entries = false
136
137 static void init();
138
139 int mark_dependent_nmethods(DepChange& changes);
140 void add_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
141 void remove_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);
142 int remove_all_dependents();
143
144 void expunge_stale_entries();
145
146 // Unsafe deallocation of nmethodBuckets. Used in IK::release_C_heap_structures
147 // to clean up the context possibly containing live entries pointing to unloaded nmethods.
148 void wipe();
149
150 #ifndef PRODUCT
151 void print_dependent_nmethods(bool verbose);
152 bool is_dependent_nmethod(nmethod* nm);
153 bool find_stale_entries();
154 #endif //PRODUCT
155 };
156 #endif // SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP