1 /*
  2  * Copyright (c) 2014, 2025, 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 "jfr/leakprofiler/leakProfiler.hpp"
 26 #include "jfr/leakprofiler/startOperation.hpp"
 27 #include "jfr/leakprofiler/stopOperation.hpp"
 28 #include "jfr/leakprofiler/checkpoint/eventEmitter.hpp"
 29 #include "jfr/leakprofiler/sampling/objectSampler.hpp"
 30 #include "jfr/recorder/service/jfrOptionSet.hpp"
 31 #include "logging/log.hpp"
 32 #include "memory/iterator.hpp"
 33 #include "runtime/javaThread.inline.hpp"
 34 #include "runtime/vmThread.hpp"
 35 
 36 bool LeakProfiler::is_supported() {
 37   if (UseCompactObjectHeaders || UseShenandoahGC) {
 38     // 1. With a 32-bit mark word in Lilliput2, we don't have enough unused
 39     //    bits to store edge index information in the mark word
 40     // 2. Even without compressed object headers, with Shenandoah, we don't
 41     //    have enough free bits in the mark word because of needing that
 42     //    space for forwarding pointers in the evacuation & update refs phase.
 43     return false;
 44   }
 45   return true;
 46 }
 47 
 48 bool LeakProfiler::is_running() {
 49   return ObjectSampler::is_created();
 50 }
 51 
 52 bool LeakProfiler::start(int sample_count) {
 53   if (is_running()) {
 54     return true;
 55   }
 56 
 57   // Allows user to disable leak profiler on command line by setting queue size to zero.
 58   if (sample_count == 0) {
 59     return false;
 60   }
 61 
 62   // Exit cleanly if not supported
 63   if (!is_supported()) {
 64     log_trace(jfr, system)("Object sampling is not supported");
 65     return false;
 66   }
 67 
 68   assert(!is_running(), "invariant");
 69   assert(sample_count > 0, "invariant");
 70 
 71   // schedule the safepoint operation for installing the object sampler
 72   StartOperation op(sample_count);
 73   VMThread::execute(&op);
 74 
 75   if (!is_running()) {
 76     log_trace(jfr, system)("Object sampling could not be started because the sampler could not be allocated");
 77     return false;
 78   }
 79   assert(is_running(), "invariant");
 80   log_trace(jfr, system)("Object sampling started");
 81   return true;
 82 }
 83 
 84 bool LeakProfiler::stop() {
 85   if (!is_running()) {
 86     return false;
 87   }
 88 
 89   // schedule the safepoint operation for uninstalling and destroying the object sampler
 90   StopOperation op;
 91   VMThread::execute(&op);
 92 
 93   assert(!is_running(), "invariant");
 94   log_trace(jfr, system)("Object sampling stopped");
 95   return true;
 96 }
 97 
 98 void LeakProfiler::emit_events(int64_t cutoff_ticks, bool emit_all, bool skip_bfs) {
 99   if (!is_running()) {
100     return;
101   }
102   // exclusive access to object sampler instance
103   ObjectSampler* const sampler = ObjectSampler::acquire();
104   assert(sampler != nullptr, "invariant");
105   EventEmitter::emit(sampler, cutoff_ticks, emit_all, skip_bfs);
106   ObjectSampler::release();
107 }
108 
109 void LeakProfiler::sample(HeapWord* object, size_t size, JavaThread* thread) {
110   assert(is_running(), "invariant");
111   assert(thread != nullptr, "invariant");
112   assert(thread->thread_state() == _thread_in_vm, "invariant");
113 
114   // exclude compiler threads
115   if (thread->is_hidden_from_external_view()) {
116     return;
117   }
118 
119   ObjectSampler::sample(object, size, thread);
120 }