root.cc revision 8332:23711432221f 
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/root.hh"
37
38Root *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 */
46void
47Root::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
67void
68Root::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.
85void
86Root::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.
95void
96Root::timeSyncSpinThreshold(Time newThreshold)
97{
98    bool en = timeSyncEnabled();
99    _spinThreshold = newThreshold;
100    timeSyncEnable(en);
101}
102
103Root::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
114void
115Root::initState()
116{
117    timeSyncEnable(params()->time_sync_enable);
118}
119
120void
121Root::loadState(Checkpoint *cp)
122{
123    timeSyncEnable(params()->time_sync_enable);
124}
125
126Root *
127RootParams::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}
137