src/sim/root.cc

   1 /*
   2  * Copyright (c) 2002-2005 The Regents of The University of Michigan
   3  * Copyright (c) 2011 Advanced Micro Devices, Inc.
   4  * All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions are
   8  * met: redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer;
  10  * redistributions in binary form must reproduce the above copyright
  11  * notice, this list of conditions and the following disclaimer in the
  12  * documentation and/or other materials provided with the distribution;
  13  * neither the name of the copyright holders nor the names of its
  14  * contributors may be used to endorse or promote products derived from
  15  * this software without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  20  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  21  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  22  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  23  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  27  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28  *
  29  * Authors: Nathan Binkert
  30  *          Steve Reinhardt
  31  *          Gabe Black
  32  */
  33
  34 #include "base/logging.hh"
  35 #include "base/trace.hh"
  36 #include "config/the_isa.hh"
  37 #include "debug/TimeSync.hh"
  38 #include "sim/eventq_impl.hh"
  39 #include "sim/full_system.hh"
  40 #include "sim/root.hh"
  41
  42 Root *Root::_root = NULL;
  43
  44 /*
  45  * This function is called periodically by an event in M5 and ensures that
  46  * at least as much real time has passed between invocations as simulated time.
  47  * If not, the function either sleeps, or if the difference is small enough
  48  * spin waits.
  49  */
  50 void
  51 Root::timeSync()
  52 {
  53     Time cur_time, diff, period = timeSyncPeriod();
  54
  55     do {
  56         cur_time.setTimer();
  57         diff = cur_time - lastTime;
  58         Time remainder = period - diff;
  59         if (diff < period && remainder > _spinThreshold) {
  60             DPRINTF(TimeSync, "Sleeping to sync with real time.\n");
  61             // Sleep until the end of the period, or until a signal.
  62             sleep(remainder);
  63             // Refresh the current time.
  64             cur_time.setTimer();
  65         }
  66     } while (diff < period);
  67     lastTime = cur_time;
  68     schedule(&syncEvent, curTick() + _periodTick);
  69 }
  70
  71 void
  72 Root::timeSyncEnable(bool en)
  73 {
  74     if (en == _enabled)
  75         return;
  76     _enabled = en;
  77     if (_enabled) {
  78         // Get event going.
  79         Tick periods = ((curTick() + _periodTick - 1) / _periodTick);
  80         Tick nextPeriod = periods * _periodTick;
  81         schedule(&syncEvent, nextPeriod);
  82     } else {
  83         // Stop event.
  84         deschedule(&syncEvent);
  85     }
  86 }
  87
  88 /// Configure the period for time sync events.
  89 void
  90 Root::timeSyncPeriod(Time newPeriod)
  91 {
  92     bool en = timeSyncEnabled();
  93     _period = newPeriod;
  94     _periodTick = _period.getTick();
  95     timeSyncEnable(en);
  96 }
  97
  98 /// Set the threshold for time remaining to spin wait.
  99 void
 100 Root::timeSyncSpinThreshold(Time newThreshold)
 101 {
 102     bool en = timeSyncEnabled();
 103     _spinThreshold = newThreshold;
 104     timeSyncEnable(en);
 105 }
 106
 107 Root::Root(RootParams *p)
 108     : SimObject(p), _enabled(false), _periodTick(p->time_sync_period),
 109       syncEvent([this]{ timeSync(); }, name())
 110 {
 111     _period.setTick(p->time_sync_period);
 112     _spinThreshold.setTick(p->time_sync_spin_threshold);
 113
 114     assert(_root == NULL);
 115     _root = this;
 116     lastTime.setTimer();
 117
 118     simQuantum = p->sim_quantum;
 119 }
 120
 121 void
 122 Root::startup()
 123 {
 124     timeSyncEnable(params()->time_sync_enable);
 125 }
 126
 127 void
 128 Root::serialize(CheckpointOut &cp) const
 129 {
 130     SERIALIZE_SCALAR(FullSystem);
 131     std::string isa = THE_ISA_STR;
 132     SERIALIZE_SCALAR(isa);
 133 }
 134
 135
 136 bool FullSystem;
 137 unsigned int FullSystemInt;
 138
 139 Root *
 140 RootParams::create()
 141 {
 142     static bool created = false;
 143     if (created)
 144         panic("only one root object allowed!");
 145
 146     created = true;
 147
 148     FullSystem = full_system;
 149     FullSystemInt = full_system ? 1 : 0;
 150
 151     return new Root(this);
 152 }