root.cc revision 8801:1a84c6a81299 
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
39Root *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 */
47void
48Root::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
68void
69Root::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.
86void
87Root::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.
96void
97Root::timeSyncSpinThreshold(Time newThreshold)
98{
99    bool en = timeSyncEnabled();
100    _spinThreshold = newThreshold;
101    timeSyncEnable(en);
102}
103
104Root::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
115void
116Root::initState()
117{
118    timeSyncEnable(params()->time_sync_enable);
119}
120
121void
122Root::loadState(Checkpoint *cp)
123{
124    timeSyncEnable(params()->time_sync_enable);
125}
126
127bool FullSystem;
128
129Root *
130RootParams::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}
142