scheduler.cc revision 13064:e06421881cec 
1/*
2 * Copyright 2018 Google, Inc.
3 *
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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#include "systemc/core/kernel.hh"
36#include "systemc/ext/core/sc_main.hh"
37
38namespace sc_gem5
39{
40
41Scheduler::Scheduler() :
42    eq(nullptr), readyEvent(this, false, ReadyPriority),
43    pauseEvent(this, false, PausePriority),
44    stopEvent(this, false, StopPriority),
45    scMain(nullptr),
46    starvationEvent(this, false, StarvationPriority),
47    _started(false), _paused(false), _stopped(false),
48    maxTickEvent(this, false, MaxTickPriority),
49    _numCycles(0), _current(nullptr), initReady(false),
50    runOnce(false)
51{}
52
53void
54Scheduler::prepareForInit()
55{
56    for (Process *p = toFinalize.getNext(); p; p = toFinalize.getNext()) {
57        p->finalize();
58        p->popListNode();
59    }
60
61    for (Process *p = initList.getNext(); p; p = initList.getNext()) {
62        p->finalize();
63        p->popListNode();
64        p->ready();
65    }
66
67    for (auto ets: eventsToSchedule)
68        eq->schedule(ets.first, ets.second);
69    eventsToSchedule.clear();
70
71    if (_started)
72        eq->schedule(&maxTickEvent, maxTick);
73
74    initReady = true;
75}
76
77void
78Scheduler::reg(Process *p)
79{
80    if (initReady) {
81        // If we're past initialization, finalize static sensitivity.
82        p->finalize();
83        // Mark the process as ready.
84        p->ready();
85    } else {
86        // Otherwise, record that this process should be initialized once we
87        // get there.
88        initList.pushLast(p);
89    }
90}
91
92void
93Scheduler::dontInitialize(Process *p)
94{
95    if (initReady) {
96        // Pop this process off of the ready list.
97        p->popListNode();
98    } else {
99        // Push this process onto the list of processes which still need
100        // their static sensitivity to be finalized. That implicitly pops it
101        // off the list of processes to be initialized/marked ready.
102        toFinalize.pushLast(p);
103    }
104}
105
106void
107Scheduler::yield()
108{
109    _current = readyList.getNext();
110    if (!_current) {
111        // There are no more processes, so return control to evaluate.
112        Fiber::primaryFiber()->run();
113    } else {
114        _current->popListNode();
115        // Switch to whatever Fiber is supposed to run this process. All
116        // Fibers which aren't running should be parked at this line.
117        _current->fiber()->run();
118        // If the current process needs to be manually started, start it.
119        if (_current && _current->needsStart())
120            _current->run();
121    }
122    if (_current && _current->excWrapper) {
123        // Make sure this isn't a method process.
124        assert(!_current->needsStart());
125        auto ew = _current->excWrapper;
126        _current->excWrapper = nullptr;
127        ew->throw_it();
128    }
129}
130
131void
132Scheduler::ready(Process *p)
133{
134    // Clump methods together to minimize context switching.
135    if (p->procKind() == ::sc_core::SC_METHOD_PROC_)
136        readyList.pushFirst(p);
137    else
138        readyList.pushLast(p);
139
140    scheduleReadyEvent();
141}
142
143void
144Scheduler::requestUpdate(Channel *c)
145{
146    updateList.pushLast(c);
147    if (eq)
148        scheduleReadyEvent();
149}
150
151void
152Scheduler::scheduleReadyEvent()
153{
154    // Schedule the evaluate and update phases.
155    if (!readyEvent.scheduled()) {
156        panic_if(!eq, "Need to schedule ready, but no event manager.\n");
157        eq->schedule(&readyEvent, eq->getCurTick());
158        if (starvationEvent.scheduled())
159            eq->deschedule(&starvationEvent);
160    }
161}
162
163void
164Scheduler::scheduleStarvationEvent()
165{
166    if (!starvationEvent.scheduled()) {
167        panic_if(!eq, "Need to schedule starvation event, "
168                "but no event manager.\n");
169        eq->schedule(&starvationEvent, eq->getCurTick());
170        if (readyEvent.scheduled())
171            eq->deschedule(&readyEvent);
172    }
173}
174
175void
176Scheduler::runReady()
177{
178    bool empty = readyList.empty();
179
180    // The evaluation phase.
181    do {
182        yield();
183    } while (!readyList.empty());
184
185    if (!empty)
186        _numCycles++;
187
188    // The update phase.
189    update();
190
191    if (starved() && !runToTime)
192        scheduleStarvationEvent();
193
194    // The delta phase.
195    for (auto &e: deltas)
196        e->run();
197    deltas.clear();
198
199    if (runOnce)
200        schedulePause();
201}
202
203void
204Scheduler::update()
205{
206    Channel *channel = updateList.getNext();
207    while (channel) {
208        channel->popListNode();
209        channel->update();
210        channel = updateList.getNext();
211    }
212}
213
214void
215Scheduler::pause()
216{
217    _paused = true;
218    kernel->status(::sc_core::SC_PAUSED);
219    runOnce = false;
220    scMain->run();
221}
222
223void
224Scheduler::stop()
225{
226    _stopped = true;
227    kernel->stop();
228    runOnce = false;
229    scMain->run();
230}
231
232void
233Scheduler::start(Tick max_tick, bool run_to_time)
234{
235    // We should be running from sc_main. Keep track of that Fiber to return
236    // to later.
237    scMain = Fiber::currentFiber();
238
239    _started = true;
240    _paused = false;
241    _stopped = false;
242    runToTime = run_to_time;
243
244    maxTick = max_tick;
245
246    if (starved() && !runToTime)
247        return;
248
249    if (initReady) {
250        kernel->status(::sc_core::SC_RUNNING);
251        eq->schedule(&maxTickEvent, maxTick);
252    }
253
254    // Return to gem5 to let it run events, etc.
255    Fiber::primaryFiber()->run();
256
257    if (pauseEvent.scheduled())
258        eq->deschedule(&pauseEvent);
259    if (stopEvent.scheduled())
260        eq->deschedule(&stopEvent);
261    if (maxTickEvent.scheduled())
262        eq->deschedule(&maxTickEvent);
263    if (starvationEvent.scheduled())
264        eq->deschedule(&starvationEvent);
265}
266
267void
268Scheduler::oneCycle()
269{
270    runOnce = true;
271    start(::MaxTick, false);
272}
273
274void
275Scheduler::schedulePause()
276{
277    if (pauseEvent.scheduled())
278        return;
279
280    eq->schedule(&pauseEvent, eq->getCurTick());
281}
282
283void
284Scheduler::scheduleStop(bool finish_delta)
285{
286    if (stopEvent.scheduled())
287        return;
288
289    if (!finish_delta) {
290        // If we're not supposed to finish the delta cycle, flush the list
291        // of ready processes, scheduled updates, and delta notifications.
292        Process *p;
293        while ((p = readyList.getNext()))
294            p->popListNode();
295        Channel *c;
296        while ((c = updateList.getNext()))
297            c->popListNode();
298        for (auto &e: deltas)
299            e->deschedule();
300        deltas.clear();
301    }
302    eq->schedule(&stopEvent, eq->getCurTick());
303}
304
305Scheduler scheduler;
306
307} // namespace sc_gem5
308