1 /* 2 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved. 3 * Copyright (c) 2018, Google and/or its affiliates. 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 RUNTIME_THREADHEAPSAMPLER_HPP 27 #define RUNTIME_THREADHEAPSAMPLER_HPP 28 29 #include "memory/allocation.hpp" 30 31 class ThreadHeapSampler { 32 private: 33 // Statics for the fast log 34 static const int FastLogNumBits = 10; 35 static const int FastLogMask = (1 << FastLogNumBits) - 1; 36 37 size_t _bytes_until_sample; 38 // Cheap random number generator 39 static uint64_t _rnd; 40 static bool _log_table_initialized; 41 42 static double _log_table[1<<FastLogNumBits]; // Constant 43 static volatile int _sampling_interval; 44 45 void pick_next_geometric_sample(); 46 void pick_next_sample(size_t overflowed_bytes = 0); 47 48 // Used for assertion mode to determine if there is a path to a TLAB slow path 49 // without a collector present. 50 size_t _collectors_present; 51 52 static double fast_log2(const double& d); 53 static bool init_log_table(); 54 uint64_t next_random(uint64_t rnd); 55 56 public: 57 ThreadHeapSampler() : _bytes_until_sample(0) { 58 _rnd = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(this)); 59 if (_rnd == 0) { 60 _rnd = 1; 61 } 62 63 _collectors_present = 0; 64 } 65 66 size_t bytes_until_sample() { return _bytes_until_sample; } 67 void set_bytes_until_sample(size_t bytes) { _bytes_until_sample = bytes; } 68 69 void check_for_sampling(oop obj, size_t size_in_bytes, size_t bytes_allocated_before); 70 71 static void set_sampling_interval(int sampling_interval); 72 static int get_sampling_interval(); 73 }; 74 75 #endif // SHARE_RUNTIME_THREADHEAPSAMPLER_HPP