/* * Copyright (c) 2018, 2021, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2018, Google and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * #include "precompiled.hpp" #include "logging/log.hpp" #include "logging/logTag.hpp" #include "prims/jvmtiExport.hpp" #include "runtime/atomic.hpp" #include "runtime/handles.inline.hpp" #include "runtime/sharedRuntime.hpp" #include "runtime/threadHeapSampler.hpp" // Cheap random number generator. // Default is 512kb. volatile int ThreadHeapSampler::_sampling_interval = 512 * 1024;// Statics for the fast log static const int FastLogNumBits = 10;static const int FastLogCount = 1 << FastLogNumBits;static const int FastLogMask = FastLogCount - 1;static const double log_table[FastLogCount] = {#ifndef PRODUCTstatic double log_table_value(int i) {return (log(1.0 + static_cast <double >(i + 0.5) / FastLogCount) / log(2.0));// Ensure initialization checks only happen once during bootstrap static volatile bool log_table_checked = false ;// Sanity check all log_table values or print it out if running // -Xlog:heapsampling+generate::none static void verify_or_generate_log_table() {true ;"table size should be power of two and at least 4" );if (log_is_enabled(Info,heapsampling,generate)) {"FastLogCount = %d" , FastLogCount);"static const double log_table[FastLogCount] = {" );int i = 0;for (; i < FastLogCount; i += 4) {double v1 = log_table_value(i);double v2 = log_table_value(i + 1);double v3 = log_table_value(i + 2);double v4 = log_table_value(i + 3);" %.15f, %.15f, %.15f, %.15f," , v1, v2, v3, v4);"};" );"post-loop invariant" );else {// sanity check log_table - disabled when generating for (int i = 0; i < FastLogCount; i++) {"log_table deviates too much at index: %d %.15f %.15f" ,#endif // Returns the next prng value. // pRNG is: aX+b mod c with a = 0x5DEECE66D, b = 0xB, c = 1<<48 // This is the lrand64 generator. const uint64_t PrngMult = 0x5DEECE66DLL;const uint64_t PrngAdd = 0xB;const uint64_t PrngModPower = 48;const uint64_t PrngModMask = ((uint64_t)1 << PrngModPower) - 1;//assert(IS_SAFE_SIZE_MUL(PrngMult, rnd), "Overflow on multiplication."); //assert(IS_SAFE_SIZE_ADD(PrngMult * rnd, PrngAdd), "Overflow on addition."); return (PrngMult * rnd + PrngAdd) & PrngModMask;double ThreadHeapSampler::fast_log2(const double & d) {"bad value passed to assert" );sizeof (d) == sizeof (x),"double and uint64_t do not have the same size" );reinterpret_cast <const uint64_t*>(&d);const uint32_t x_high = x >> 32;"FastLogNumBits should be less than 20." );const uint32_t y = x_high >> (20 - FastLogNumBits) & FastLogMask;const int32_t exponent = ((x_high >> 20) & 0x7FF) - 1023;return exponent + log_table[y];// Generates a geometric variable with the specified mean (512K by default). // This is done by generating a random number between 0 and 1 and applying // the inverse cumulative distribution function for an exponential. // Specifically: Let m be the inverse of the sample interval, then // the probability distribution function is m*exp(-mx) so the CDF is // p = 1 - exp(-mx), so // q = 1 - p = exp(-mx) // log_e(q) = -mx // -log_e(q)/m = x // log_2(q) * (-log_e(2) * 1/m) = x // In the code, q is actually in the range 1 to 2**26, hence the -26 below void ThreadHeapSampler::pick_next_geometric_sample() {// Take the top 26 bits as the random number // (This plus a 1<<58 sampling bound gives a max possible step of // 5194297183973780480 bytes. In this case, // for sample_parameter = 1<<19, max possible step is // 9448372 bytes (24 bits). const uint64_t PrngModPower = 48; // Number of bits in prng // The uint32_t cast is to prevent a (hard-to-reproduce) NAN // under piii debug for some binaries. double q = static_cast <uint32_t>(_rnd >> (PrngModPower - 26)) + 1.0;// Put the computed p-value through the CDF of a geometric. // For faster performance (save ~1/20th exec time), replace // min(0.0, FastLog2(q) - 26) by (Fastlog2(q) - 26.000705) // The value 26.000705 is used rather than 26 to compensate // for inaccuracies in FastLog2 which otherwise result in a // negative answer. double log_val = (fast_log2(q) - 26);double result =static_cast <double >(SIZE_MAX), "Result is not in an acceptable range." );static_cast <size_t>(result);void ThreadHeapSampler::pick_next_sample(size_t overflowed_bytes) {#ifndef PRODUCTif (!log_table_checked) {#endif // Explicitly test if the sampling interval is 0, return 0 to sample every // allocation. if (get_sampling_interval() == 0) {return ;void ThreadHeapSampler::check_for_sampling(oop obj, size_t allocation_size, size_t bytes_since_allocation) {// If not yet time for a sample, skip it. if (total_allocated_bytes < _bytes_until_sample) {return ;int ThreadHeapSampler::get_sampling_interval() {return Atomic::load_acquire(&_sampling_interval);void ThreadHeapSampler::set_sampling_interval(int sampling_interval) {quality 95%
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