1 /*
   2  * Copyright (c) 2001, 2020, Oracle 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 #include "precompiled.hpp"
  26 #include "gc/g1/g1MMUTracker.hpp"
  27 #include "gc/g1/g1Trace.hpp"
  28 #include "logging/log.hpp"
  29 #include "runtime/mutexLocker.hpp"
  30 #include "utilities/ostream.hpp"
  31 
  32 // can't rely on comparing doubles with tolerating a small margin for error
  33 #define SMALL_MARGIN 0.0000001
  34 #define is_double_leq_0(_value) ( (_value) < SMALL_MARGIN )
  35 #define is_double_leq(_val1, _val2) is_double_leq_0((_val1) - (_val2))
  36 #define is_double_geq(_val1, _val2) is_double_leq_0((_val2) - (_val1))
  37 
  38 /***** ALL TIMES ARE IN SECS!!!!!!! *****/
  39 
  40 G1MMUTracker::G1MMUTracker(double time_slice, double max_gc_time) :
  41   _time_slice(time_slice),
  42   _max_gc_time(max_gc_time) { }
  43 
  44 G1MMUTrackerQueue::G1MMUTrackerQueue(double time_slice, double max_gc_time) :
  45   G1MMUTracker(time_slice, max_gc_time),
  46   _head_index(0),
  47   _tail_index(trim_index(_head_index+1)),
  48   _no_entries(0) { }
  49 
  50 void G1MMUTrackerQueue::remove_expired_entries(double current_time) {
  51   double limit = current_time - _time_slice;
  52   while (_no_entries > 0) {
  53     if (is_double_geq(limit, _array[_tail_index].end_time())) {
  54       _tail_index = trim_index(_tail_index + 1);
  55       --_no_entries;
  56     } else
  57       return;
  58   }
  59   guarantee(_no_entries == 0, "should have no entries in the array");
  60 }
  61 
  62 double G1MMUTrackerQueue::calculate_gc_time(double current_time) {
  63   double gc_time = 0.0;
  64   double limit = current_time - _time_slice;
  65   for (int i = 0; i < _no_entries; ++i) {
  66     int index = trim_index(_tail_index + i);
  67     G1MMUTrackerQueueElem *elem = &_array[index];
  68     if (elem->end_time() > limit) {
  69       if (elem->start_time() > limit)
  70         gc_time += elem->duration();
  71       else
  72         gc_time += elem->end_time() - limit;
  73     }
  74   }
  75   return gc_time;
  76 }
  77 
  78 void G1MMUTrackerQueue::add_pause(double start, double end) {
  79   double duration = end - start;
  80 
  81   remove_expired_entries(end);
  82   if (_no_entries == QueueLength) {
  83     // OK, we've filled up the queue. There are a few ways
  84     // of dealing with this "gracefully"
  85     //   increase the array size (:-)
  86     //   remove the oldest entry (this might allow more GC time for
  87     //     the time slice than what's allowed) - this is what we
  88     //     currently do
  89     //   consolidate the two entries with the minimum gap between them
  90     //     (this might allow less GC time than what's allowed)
  91 
  92     // In the case where ScavengeALot is true, such overflow is not
  93     // uncommon; in such cases, we can, without much loss of precision
  94     // or performance (we are GC'ing most of the time anyway!),
  95     // simply overwrite the oldest entry in the tracker.
  96 
  97     _head_index = trim_index(_head_index + 1);
  98     assert(_head_index == _tail_index, "Because we have a full circular buffer");
  99     _tail_index = trim_index(_tail_index + 1);
 100   } else {
 101     _head_index = trim_index(_head_index + 1);
 102     ++_no_entries;
 103   }
 104   _array[_head_index] = G1MMUTrackerQueueElem(start, end);
 105 
 106   // Current entry needs to be added before calculating the value
 107   double slice_time = calculate_gc_time(end);
 108   G1MMUTracer::report_mmu(_time_slice, slice_time, _max_gc_time);
 109 
 110   if (slice_time < _max_gc_time) {
 111     log_debug(gc, mmu)("MMU: %.1lfms (%.1lfms/%.1lfms)",
 112                        slice_time * 1000.0, _max_gc_time * 1000.0, _time_slice * 1000);
 113   } else {
 114     log_info(gc, mmu)("MMU target violated: %.1lfms (%.1lfms/%.1lfms)",
 115                       slice_time * 1000.0, _max_gc_time * 1000.0, _time_slice * 1000);
 116   }
 117 }
 118 
 119 double G1MMUTrackerQueue::when_sec(double current_time, double pause_time) {
 120   // if the pause is over the maximum, just assume that it's the maximum
 121   double adjusted_pause_time =
 122     (pause_time > max_gc_time()) ? max_gc_time() : pause_time;
 123   double earliest_end = current_time + adjusted_pause_time;
 124   double limit = earliest_end - _time_slice;
 125   double gc_time = calculate_gc_time(earliest_end);
 126   double diff = gc_time + adjusted_pause_time - max_gc_time();
 127   if (is_double_leq_0(diff))
 128     return 0.0;
 129 
 130   int index = _tail_index;
 131   while ( 1 ) {
 132     G1MMUTrackerQueueElem *elem = &_array[index];
 133     if (elem->end_time() > limit) {
 134       if (elem->start_time() > limit)
 135         diff -= elem->duration();
 136       else
 137         diff -= elem->end_time() - limit;
 138       if (is_double_leq_0(diff))
 139         return  elem->end_time() + diff + _time_slice - adjusted_pause_time - current_time;
 140     }
 141     index = trim_index(index+1);
 142     guarantee(index != trim_index(_head_index + 1), "should not go past head");
 143   }
 144 }