src/sim/root.cc

   1 /*
   2  * Copyright (c) 2002-2005 The Regents of The University of Michigan
   3  * Copyright (c) 2011 Advanced Micro Devices
   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/root.hh"
  37
  38 Root *Root::_root = NULL;
  39
  40 /*
  41  * This function is called periodically by an event in M5 and ensures that
  42  * at least as much real time has passed between invocations as simulated time.
  43  * If not, the function either sleeps, or if the difference is small enough
  44  * spin waits.
  45  */
  46 void
  47 Root::timeSync()
  48 {
  49     Time cur_time, diff, period = timeSyncPeriod();
  50
  51     do {
  52         cur_time.setTimer();
  53         diff = cur_time - lastTime;
  54         Time remainder = period - diff;
  55         if (diff < period && remainder > _spinThreshold) {
  56             DPRINTF(TimeSync, "Sleeping to sync with real time.\n");
  57             // Sleep until the end of the period, or until a signal.
  58             sleep(remainder);
  59             // Refresh the current time.
  60             cur_time.setTimer();
  61         }
  62     } while (diff < period);
  63     lastTime = cur_time;
  64     schedule(&syncEvent, curTick() + _periodTick);
  65 }
  66
  67 void
  68 Root::timeSyncEnable(bool en)
  69 {
  70     if (en == _enabled)
  71         return;
  72     _enabled = en;
  73     if (_enabled) {
  74         // Get event going.
  75         Tick periods = ((curTick() + _periodTick - 1) / _periodTick);
  76         Tick nextPeriod = periods * _periodTick;
  77         schedule(&syncEvent, nextPeriod);
  78     } else {
  79         // Stop event.
  80         deschedule(&syncEvent);
  81     }
  82 }
  83
  84 /// Configure the period for time sync events.
  85 void
  86 Root::timeSyncPeriod(Time newPeriod)
  87 {
  88     bool en = timeSyncEnabled();
  89     _period = newPeriod;
  90     _periodTick = _period.getTick();
  91     timeSyncEnable(en);
  92 }
  93
  94 /// Set the threshold for time remaining to spin wait.
  95 void
  96 Root::timeSyncSpinThreshold(Time newThreshold)
  97 {
  98     bool en = timeSyncEnabled();
  99     _spinThreshold = newThreshold;
 100     timeSyncEnable(en);
 101 }
 102
 103 Root::Root(RootParams *p) : SimObject(p), _enabled(false),
 104     _periodTick(p->time_sync_period), syncEvent(this)
 105 {
 106     _period.setTick(p->time_sync_period);
 107     _spinThreshold.setTick(p->time_sync_spin_threshold);
 108
 109     assert(_root == NULL);
 110     _root = this;
 111     lastTime.setTimer();
 112 }
 113
 114 void
 115 Root::initState()
 116 {
 117     timeSyncEnable(params()->time_sync_enable);
 118 }
 119
 120 void
 121 Root::loadState(Checkpoint *cp)
 122 {
 123     timeSyncEnable(params()->time_sync_enable);
 124 }
 125
 126 Root *
 127 RootParams::create()
 128 {
 129     static bool created = false;
 130     if (created)
 131         panic("only one root object allowed!");
 132
 133     created = true;
 134
 135     return new Root(this);
 136 }