1 /* 2 * Copyright (c) 2017, Google 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_RUNTIME_HEAPMONITORING_HPP 26 #define SHARE_VM_RUNTIME_HEAPMONITORING_HPP 27 28 #include "gc/shared/referenceProcessor.hpp" 29 #include "runtime/sharedRuntime.hpp" 30 31 // Support class for sampling heap allocations across the VM. 32 class HeapMonitoring : AllStatic { 33 private: 34 // Cheap random number generator 35 static uint64_t _rnd; 36 static jint _monitoring_rate; 37 static bool _enabled; 38 39 // Statics for the fast log 40 static const int FastLogNumBits = 10; 41 static const int FastLogMask = (1 << FastLogNumBits) - 1; 42 static double _log_table[1<<FastLogNumBits]; // Constant 43 44 static void pick_next_sample(JavaThread *t); 45 46 // Returns the next prng value. 47 // pRNG is: aX+b mod c with a = 0x5DEECE66D, b = 0xB, c = 1<<48 48 // This is the lrand64 generator. 49 static inline uint64_t next_random(uint64_t rnd) { 50 const uint64_t PrngMult = 0x5DEECE66DLL; 51 const uint64_t prng_add = 0xB; 52 const uint64_t prng_mod_power = 48; 53 const uint64_t prng_mod_mask = right_n_bits(prng_mod_power); 54 return (PrngMult * rnd + prng_add) & prng_mod_mask; 55 } 56 57 static inline double fast_log2(const double & d) { 58 assert(d>0, "bad value passed to assert"); 59 uint64_t x = 0; 60 memcpy(&x, &d, sizeof(uint64_t)); 61 const uint32_t x_high = x >> 32; 62 const uint32_t y = x_high >> (20 - FastLogNumBits) & FastLogMask; 63 const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023; 64 return exponent + _log_table[y]; 65 } 66 67 public: 68 /* 69 * General note: currently none of these methods are deemed thread-safe. 70 */ 71 72 // First method called by user to start the profiler: 73 // - Note: the lower the monitoring rate, the higher the overhead incurred. 74 static void initialize_profiling(jint monitoring_rate, jint max_gc_storage); 75 76 // Pick the next sample for a given size_t pointer using a geometric variable 77 // with specified mean. The specified mean is provided via the 78 // initialize_profiling method. 79 static void pick_next_sample(size_t *ptr); 80 81 // Get live/garbage traces and provide a method to release the traces. 82 static void get_live_traces(jvmtiStackTraces* stack_traces); 83 static void get_garbage_traces(jvmtiStackTraces* stack_traces); 84 static void get_frequent_garbage_traces(jvmtiStackTraces* stack_traces); 85 static void release_traces(jvmtiStackTraces *trace_info); 86 87 static void get_sampling_statistics(jvmtiHeapSamplingStats* stats); 88 static void stop_profiling(); 89 90 // Called when o is to be sampled from a given thread and a given size. 91 static void object_alloc_do_sample(Thread *t, oopDesc *o, intx size_in_bytes); 92 93 // Called to clean up oops that have been saved by our sampling function, 94 // but which no longer have other references in the heap. 95 static void weak_oops_do(BoolObjectClosure* is_alive, OopClosure *f); 96 static void weak_oops_do(OopClosure* oop_closure) { 97 AlwaysTrueClosure _always_true; 98 weak_oops_do(&_always_true, oop_closure); 99 } 100 101 static bool enabled() { 102 return _enabled; 103 } 104 }; 105 106 #endif // SHARE_VM_RUNTIME_HEAPMONITORING_HPP