1 /*
2 * Copyright (c) 2019, 2021, 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 #include "precompiled.hpp"
26 #include "jfr/jfrEvents.hpp"
27 #include "jfr/leakprofiler/chains/edgeStore.hpp"
28 #include "jfr/leakprofiler/chains/pathToGcRootsOperation.hpp"
29 #include "jfr/leakprofiler/checkpoint/eventEmitter.hpp"
30 #include "jfr/leakprofiler/checkpoint/objectSampleCheckpoint.hpp"
31 #include "jfr/leakprofiler/sampling/objectSample.hpp"
32 #include "jfr/leakprofiler/sampling/objectSampler.hpp"
33 #include "jfr/leakprofiler/utilities/unifiedOopRef.inline.hpp"
34 #include "logging/log.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "oops/markWord.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/mutexLocker.hpp"
39 #include "runtime/thread.inline.hpp"
40 #include "runtime/vmThread.hpp"
41
42 EventEmitter::EventEmitter(const JfrTicks& start_time, const JfrTicks& end_time) :
43 _start_time(start_time),
44 _end_time(end_time),
45 _thread(Thread::current()),
46 _jfr_thread_local(_thread->jfr_thread_local()),
47 _thread_id(_thread->jfr_thread_local()->thread_id()) {}
48
49 EventEmitter::~EventEmitter() {
50 // restore / reset thread local stack trace and thread id
51 _jfr_thread_local->set_thread_id(_thread_id);
52 _jfr_thread_local->clear_cached_stack_trace();
53 }
54
55 void EventEmitter::emit(ObjectSampler* sampler, int64_t cutoff_ticks, bool emit_all, bool skip_bfs) {
56 assert(sampler != NULL, "invariant");
57 ResourceMark rm;
58 EdgeStore edge_store;
59 if (cutoff_ticks <= 0) {
60 // no reference chains
61 JfrTicks time_stamp = JfrTicks::now();
62 EventEmitter emitter(time_stamp, time_stamp);
63 emitter.write_events(sampler, &edge_store, emit_all);
64 return;
65 }
66 // events emitted with reference chains require a safepoint operation
67 PathToGcRootsOperation op(sampler, &edge_store, cutoff_ticks, emit_all, skip_bfs);
68 VMThread::execute(&op);
69 }
70
71 size_t EventEmitter::write_events(ObjectSampler* object_sampler, EdgeStore* edge_store, bool emit_all) {
72 assert(_thread == Thread::current(), "invariant");
73 assert(_thread->jfr_thread_local() == _jfr_thread_local, "invariant");
74 assert(object_sampler != NULL, "invariant");
75 assert(edge_store != NULL, "invariant");
76
77 const jlong last_sweep = emit_all ? max_jlong : ObjectSampler::last_sweep();
78 size_t count = 0;
79
80 // First pass associates a live sample with its immediate edge
81 // in preparation for writing checkpoint information.
82 const ObjectSample* current = object_sampler->first();
83 while (current != NULL) {
84 ObjectSample* prev = current->prev();
85 if (current->is_alive_and_older_than(last_sweep)) {
86 link_sample_with_edge(current, edge_store);
87 ++count;
88 }
89 current = prev;
90 }
91 if (count > 0) {
92 // We need to serialize the associated checkpoints and potential chains
93 // before writing the events to ensure constants are available for resolution
94 // at the time old object sample events appear in the stream.
95 ObjectSampleCheckpoint::write(object_sampler, edge_store, emit_all, _thread);
96
97 // Now we are ready to write the events
98 const ObjectSample* current = object_sampler->first();
99 while (current != NULL) {
100 ObjectSample* prev = current->prev();
101 if (current->is_alive_and_older_than(last_sweep)) {
102 write_event(current, edge_store);
103 }
104 current = prev;
105 }
106 }
107 return count;
108 }
109
110 static int array_size(const oop object) {
111 assert(object != NULL, "invariant");
112 if (object->is_array()) {
113 return arrayOop(object)->length();
114 }
115 return min_jint;
116 }
117
118 void EventEmitter::link_sample_with_edge(const ObjectSample* sample, EdgeStore* edge_store) {
119 assert(sample != NULL, "invariant");
120 assert(!sample->is_dead(), "invariant");
121 assert(edge_store != NULL, "invariant");
122 if (SafepointSynchronize::is_at_safepoint()) {
123 if (edge_store->has_leak_context(sample)) {
124 // Associated with an edge (chain) already during heap traversal.
125 return;
126 }
127 }
128 // In order to dump out a representation of the event
129 // even though the sample object was found not reachable / too long to reach,
130 // we need to register a top level edge.
131 edge_store->put(UnifiedOopRef::encode_in_native(sample->object_addr()));
132 }
133
134 void EventEmitter::write_event(const ObjectSample* sample, EdgeStore* edge_store) {
135 assert(sample != NULL, "invariant");
136 assert(!sample->is_dead(), "invariant");
137 assert(edge_store != NULL, "invariant");
138 assert(_jfr_thread_local != NULL, "invariant");
139
140 const StoredEdge* const edge = edge_store->get(sample);
141 assert(edge != NULL, "invariant");
142 assert(edge->pointee() == sample->object(), "invariant");
143 const traceid object_id = edge_store->get_id(edge);
144 assert(object_id != 0, "invariant");
145 const traceid gc_root_id = edge->gc_root_id();
146
147 Tickspan object_age = Ticks(_start_time.value()) - sample->allocation_time();
148
149 EventOldObjectSample e(UNTIMED);
150 e.set_starttime(_start_time);
151 e.set_endtime(_end_time);
152 e.set_allocationTime(sample->allocation_time());
153 e.set_objectAge(object_age);
154 e.set_lastKnownHeapUsage(sample->heap_used_at_last_gc());
155 e.set_object(object_id);
156 e.set_arrayElements(array_size(edge->pointee()));
157 e.set_root(gc_root_id);
158
159 // Temporarily assigning both the stack trace id and thread id
160 // onto the thread local data structure of the emitter thread (for the duration
161 // of the commit() call). This trick provides a means to override
162 // the event generation mechanism by injecting externally provided id's.
163 // At this particular location, it allows us to emit an old object event
164 // supplying information from where the actual sampling occurred.
165 _jfr_thread_local->set_cached_stack_trace_id(sample->stack_trace_id());
166 assert(sample->has_thread(), "invariant");
167 _jfr_thread_local->set_thread_id(sample->thread_id());
168 e.commit();
169 }