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 { 33 private: 34 // Cheap random number generator 35 static uint64_t _rnd; 36 static bool _initialized; 37 static jint _monitoring_period; 38 39 // Statics for the fast log 40 static const int kFastlogNumBits = 10; 41 static const int kFastlogMask = (1 << kFastlogNumBits) - 1; 42 static double _log_table[1<<kFastlogNumBits]; // Constant 43 44 static void pick_next_sample(JavaThread *t); 45 46 // TODO(jcbeyler): is this algorithm acceptable in open source? 47 // Returns the next prng value. 48 // pRNG is: aX+b mod c with a = 0x5DEECE66D, b = 0xB, c = 1<<48 49 // This is the lrand64 generator. 50 static inline uint64_t next_random(uint64_t rnd) { 51 const uint64_t prng_mult = 0x5DEECE66DLL; 52 const uint64_t prng_add = 0xB; 53 const uint64_t prng_mod_power = 48; 54 const uint64_t prng_mod_mask = 55 ~((~static_cast<uint64_t>(0)) << prng_mod_power); 56 return (prng_mult * rnd + prng_add) & prng_mod_mask; 57 } 58 59 // TODO(jcbeyler): is this algorithm acceptable in open source? 60 // Adapted from //util/math/fastmath.[h|cc] by Noam Shazeer 61 // This mimics the VeryFastLog2 code in those files 62 static inline double fast_log2(const double & d) { 63 assert(d>0, "bad value passed to assert"); 64 uint64_t x = 0; 65 memcpy(&x, &d, sizeof(uint64_t)); 66 const uint32_t x_high = x >> 32; 67 const uint32_t y = x_high >> (20 - kFastlogNumBits) & kFastlogMask; 68 const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023; 69 return exponent + _log_table[y]; 70 } 71 72 public: 73 static void get_live_traces(jvmtiStackTraceData** stack_traces, jint* num_traces); 74 static void initialize_profiling(jint monitoring_period); 75 76 // Called when o is allocated, called by interpreter and C1. 77 static void object_alloc_unsized(oopDesc* o); 78 static void object_alloc(oopDesc* o, intx byte_size); 79 80 // Called when o is allocated from C2 directly, 81 // we know the thread, and we have done the sampling. 82 static void object_alloc_do_sample(Thread *t, oopDesc *o, intx size_in_bytes); 83 }; 84 85 #endif // SHARE_VM_RUNTIME_HEAPMONITORING_HPP