1 /*
   2  * Copyright (c) 2018, 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 RUNTIME_THREADHEAPSAMPLER_HPP
  26 #define RUNTIME_THREADHEAPSAMPLER_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "runtime/orderAccess.inline.hpp"
  30 
  31 class ThreadHeapSampler {
  32  private:
  33   size_t _bytes_until_sample;
  34   Thread* _thread;
  35   // Cheap random number generator
  36   static uint64_t _rnd;
  37 
  38   void pick_next_geometric_sample();
  39   void pick_next_sample(size_t overflowed_bytes = 0);
  40   static int _enabled;
  41   static int _sampling_rate;
  42 
  43   // Used for assertion mode to determine if there is a path to a TLAB slow path
  44   // without a collector present.
  45   size_t _collectors_present;
  46 
  47   static void init_log_table();
  48 
  49  public:
  50   ThreadHeapSampler() : _bytes_until_sample(0), _thread(NULL) {
  51     _rnd = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(this));
  52     if (_rnd == 0) {
  53       _rnd = 1;
  54     }
  55 
  56     _collectors_present = 0;
  57   }
  58 
  59   void set_thread(Thread* t)                     { _thread = t; }
  60 
  61   size_t bytes_until_sample()                    { return _bytes_until_sample;   }
  62   void set_bytes_until_sample(size_t bytes)      { _bytes_until_sample = bytes;  }
  63 
  64   void check_for_sampling(HeapWord* obj, size_t size_in_bytes, size_t bytes_allocated_before = 0);
  65 
  66   static int enabled() { return OrderAccess::load_acquire(&_enabled); }
  67   static void enable();
  68   static void disable() { OrderAccess::release_store(&_enabled, 0); }
  69 
  70   static void set_sampling_rate(int sampling_rate) {
  71     OrderAccess::release_store(&_sampling_rate, sampling_rate);
  72   }
  73   static int get_sampling_rate() {
  74     return OrderAccess::load_acquire(&_sampling_rate);
  75   }
  76 
  77   bool sampling_collector_present() const;
  78   bool remove_sampling_collector();
  79   bool add_sampling_collector();
  80 };
  81 
  82 #endif // SHARE_RUNTIME_THREADHEAPSAMPLER_HPP