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/misc.hh"
  35 #include "debug/TimeSync.hh"
  36 #include "sim/full_system.hh"
  37 #include "sim/root.hh"
  38
  39 Root *Root::_root = NULL;
  40
  41 /*
  42  * This function is called periodically by an event in M5 and ensures that
  43  * at least as much real time has passed between invocations as simulated time.
  44  * If not, the function either sleeps, or if the difference is small enough
  45  * spin waits.
  46  */
  47 void
  48 Root::timeSync()
  49 {
  50     Time cur_time, diff, period = timeSyncPeriod();
  51
  52     do {
  53         cur_time.setTimer();
  54         diff = cur_time - lastTime;
  55         Time remainder = period - diff;
  56         if (diff < period && remainder > _spinThreshold) {
  57             DPRINTF(TimeSync, "Sleeping to sync with real time.\n");
  58             // Sleep until the end of the period, or until a signal.
  59             sleep(remainder);
  60             // Refresh the current time.
  61             cur_time.setTimer();
  62         }
  63     } while (diff < period);
  64     lastTime = cur_time;
  65     schedule(&syncEvent, curTick() + _periodTick);
  66 }
  67
  68 void
  69 Root::timeSyncEnable(bool en)
  70 {
  71     if (en == _enabled)
  72         return;
  73     _enabled = en;
  74     if (_enabled) {
  75         // Get event going.
  76         Tick periods = ((curTick() + _periodTick - 1) / _periodTick);
  77         Tick nextPeriod = periods * _periodTick;
  78         schedule(&syncEvent, nextPeriod);
  79     } else {
  80         // Stop event.
  81         deschedule(&syncEvent);
  82     }
  83 }
  84
  85 /// Configure the period for time sync events.
  86 void
  87 Root::timeSyncPeriod(Time newPeriod)
  88 {
  89     bool en = timeSyncEnabled();
  90     _period = newPeriod;
  91     _periodTick = _period.getTick();
  92     timeSyncEnable(en);
  93 }
  94
  95 /// Set the threshold for time remaining to spin wait.
  96 void
  97 Root::timeSyncSpinThreshold(Time newThreshold)
  98 {
  99     bool en = timeSyncEnabled();
 100     _spinThreshold = newThreshold;
 101     timeSyncEnable(en);
 102 }
 103
 104 Root::Root(RootParams *p) : SimObject(p), _enabled(false),
 105     _periodTick(p->time_sync_period), syncEvent(this)
 106 {
 107     _period.setTick(p->time_sync_period);
 108     _spinThreshold.setTick(p->time_sync_spin_threshold);
 109
 110     assert(_root == NULL);
 111     _root = this;
 112     lastTime.setTimer();
 113 }
 114
 115 void
 116 Root::initState()
 117 {
 118     timeSyncEnable(params()->time_sync_enable);
 119 }
 120
 121 void
 122 Root::loadState(Checkpoint *cp)
 123 {
 124     timeSyncEnable(params()->time_sync_enable);
 125 }
 126
 127 bool FullSystem;
 128
 129 Root *
 130 RootParams::create()
 131 {
 132     static bool created = false;
 133     if (created)
 134         panic("only one root object allowed!");
 135
 136     created = true;
 137
 138     FullSystem = full_system;
 139
 140     return new Root(this);
 141 }