scheduler.cc revision 12954:8ea3a185354c 
1/*
2 * Copyright 2018 Google, Inc.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met: redistributions of source code must retain the above copyright
7 * notice, this list of conditions and the following disclaimer;
8 * redistributions in binary form must reproduce the above copyright
9 * notice, this list of conditions and the following disclaimer in the
10 * documentation and/or other materials provided with the distribution;
11 * neither the name of the copyright holders nor the names of its
12 * contributors may be used to endorse or promote products derived from
13 * this software without specific prior written permission.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
19 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
21 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 * Authors: Gabe Black
28 */
29
30#include "systemc/core/scheduler.hh"
31
32#include "base/fiber.hh"
33#include "base/logging.hh"
34#include "sim/eventq.hh"
35
36namespace sc_gem5
37{
38
39Scheduler::Scheduler() :
40    eq(nullptr), readyEvent(this, false, EventBase::Default_Pri + 1),
41    _numCycles(0), _current(nullptr)
42{}
43
44void
45Scheduler::initToReady()
46{
47    while (!initList.empty())
48        ready(initList.getNext());
49}
50
51void
52Scheduler::yield()
53{
54    _current = readyList.getNext();
55    if (!_current) {
56        // There are no more processes, so return control to evaluate.
57        Fiber::primaryFiber()->run();
58    } else {
59        _current->popListNode();
60        // Switch to whatever Fiber is supposed to run this process. All
61        // Fibers which aren't running should be parked at this line.
62        _current->fiber()->run();
63        // If the current process hasn't been started yet, start it. This
64        // should always be true for methods, but may not be true for threads.
65        if (_current && !_current->running())
66            _current->run();
67    }
68}
69
70void
71Scheduler::ready(Process *p)
72{
73    // Clump methods together to minimize context switching.
74    if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
75        readyList.pushFirst(p);
76    else
77        readyList.pushLast(p);
78
79    scheduleReadyEvent();
80}
81
82void
83Scheduler::requestUpdate(Channel *c)
84{
85    updateList.pushLast(c);
86    scheduleReadyEvent();
87}
88
89void
90Scheduler::scheduleReadyEvent()
91{
92    // Schedule the evaluate and update phases.
93    if (!readyEvent.scheduled()) {
94        panic_if(!eq, "Need to schedule ready, but no event manager.\n");
95        eq->schedule(&readyEvent, eq->getCurTick());
96    }
97}
98
99void
100Scheduler::runReady()
101{
102    bool empty = readyList.empty();
103
104    // The evaluation phase.
105    do {
106        yield();
107    } while (!readyList.empty());
108
109    if (!empty)
110        _numCycles++;
111
112    // The update phase.
113    update();
114
115    // The delta phase will happen naturally through the event queue.
116}
117
118void
119Scheduler::update()
120{
121    Channel *channel = updateList.getNext();
122    while (channel) {
123        channel->popListNode();
124        channel->update();
125        channel = updateList.getNext();
126    }
127}
128
129Scheduler scheduler;
130
131} // namespace sc_gem5
132