simulate.cc revision 10756:f9c0692f73ec 
1/*
2 * Copyright (c) 2006 The Regents of The University of Michigan
3 * Copyright (c) 2013 Advanced Micro Devices, Inc.
4 * Copyright (c) 2013 Mark D. Hill and David A. Wood
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are
9 * met: redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer;
11 * redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution;
14 * neither the name of the copyright holders nor the names of its
15 * contributors may be used to endorse or promote products derived from
16 * this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 *
30 * Authors: Nathan Binkert
31 *          Steve Reinhardt
32 */
33
34#include <mutex>
35#include <thread>
36
37#include "base/misc.hh"
38#include "base/pollevent.hh"
39#include "base/types.hh"
40#include "sim/async.hh"
41#include "sim/eventq_impl.hh"
42#include "sim/sim_events.hh"
43#include "sim/sim_exit.hh"
44#include "sim/simulate.hh"
45#include "sim/stat_control.hh"
46
47//! Mutex for handling async events.
48std::mutex asyncEventMutex;
49
50//! Global barrier for synchronizing threads entering/exiting the
51//! simulation loop.
52Barrier *threadBarrier;
53
54//! forward declaration
55Event *doSimLoop(EventQueue *);
56
57/**
58 * The main function for all subordinate threads (i.e., all threads
59 * other than the main thread).  These threads start by waiting on
60 * threadBarrier.  Once all threads have arrived at threadBarrier,
61 * they enter the simulation loop concurrently.  When they exit the
62 * loop, they return to waiting on threadBarrier.  This process is
63 * repeated until the simulation terminates.
64 */
65static void
66thread_loop(EventQueue *queue)
67{
68    while (true) {
69        threadBarrier->wait();
70        doSimLoop(queue);
71    }
72}
73
74GlobalEvent*
75getLimitEvent(void) {
76    static GlobalSimLoopExitEvent
77           simulate_limit_event(mainEventQueue[0]->getCurTick(),
78                                "simulate() limit reached", 0);
79    return &simulate_limit_event;
80}
81
82/** Simulate for num_cycles additional cycles.  If num_cycles is -1
83 * (the default), do not limit simulation; some other event must
84 * terminate the loop.  Exported to Python via SWIG.
85 * @return The SimLoopExitEvent that caused the loop to exit.
86 */
87GlobalSimLoopExitEvent *
88simulate(Tick num_cycles)
89{
90    // The first time simulate() is called from the Python code, we need to
91    // create a thread for each of event queues referenced by the
92    // instantiated sim objects.
93    static bool threads_initialized = false;
94    static std::vector<std::thread *> threads;
95
96    if (!threads_initialized) {
97        threadBarrier = new Barrier(numMainEventQueues);
98
99        // the main thread (the one we're currently running on)
100        // handles queue 0, so we only need to allocate new threads
101        // for queues 1..N-1.  We'll call these the "subordinate" threads.
102        for (uint32_t i = 1; i < numMainEventQueues; i++) {
103            threads.push_back(new std::thread(thread_loop, mainEventQueue[i]));
104        }
105
106        threads_initialized = true;
107    }
108
109    inform("Entering event queue @ %d.  Starting simulation...\n", curTick());
110
111    if (num_cycles < MaxTick - curTick())
112        num_cycles = curTick() + num_cycles;
113    else // counter would roll over or be set to MaxTick anyhow
114        num_cycles = MaxTick;
115
116    getLimitEvent()->reschedule(num_cycles);
117
118    GlobalSyncEvent *quantum_event = NULL;
119    if (numMainEventQueues > 1) {
120        if (simQuantum == 0) {
121            fatal("Quantum for multi-eventq simulation not specified");
122        }
123
124        quantum_event = new GlobalSyncEvent(curTick() + simQuantum, simQuantum,
125                            EventBase::Progress_Event_Pri, 0);
126
127        inParallelMode = true;
128    }
129
130    // all subordinate (created) threads should be waiting on the
131    // barrier; the arrival of the main thread here will satisfy the
132    // barrier, and all threads will enter doSimLoop in parallel
133    threadBarrier->wait();
134    Event *local_event = doSimLoop(mainEventQueue[0]);
135    assert(local_event != NULL);
136
137    inParallelMode = false;
138
139    // locate the global exit event and return it to Python
140    BaseGlobalEvent *global_event = local_event->globalEvent();
141    assert(global_event != NULL);
142
143    GlobalSimLoopExitEvent *global_exit_event =
144        dynamic_cast<GlobalSimLoopExitEvent *>(global_event);
145    assert(global_exit_event != NULL);
146
147    //! Delete the simulation quantum event.
148    if (quantum_event != NULL) {
149        quantum_event->deschedule();
150        delete quantum_event;
151    }
152
153    return global_exit_event;
154}
155
156/**
157 * Test and clear the global async_event flag, such that each time the
158 * flag is cleared, only one thread returns true (and thus is assigned
159 * to handle the corresponding async event(s)).
160 */
161static bool
162testAndClearAsyncEvent()
163{
164    bool was_set = false;
165    asyncEventMutex.lock();
166
167    if (async_event) {
168        was_set = true;
169        async_event = false;
170    }
171
172    asyncEventMutex.unlock();
173    return was_set;
174}
175
176/**
177 * The main per-thread simulation loop. This loop is executed by all
178 * simulation threads (the main thread and the subordinate threads) in
179 * parallel.
180 */
181Event *
182doSimLoop(EventQueue *eventq)
183{
184    // set the per thread current eventq pointer
185    curEventQueue(eventq);
186    eventq->handleAsyncInsertions();
187
188    while (1) {
189        // there should always be at least one event (the SimLoopExitEvent
190        // we just scheduled) in the queue
191        assert(!eventq->empty());
192        assert(curTick() <= eventq->nextTick() &&
193               "event scheduled in the past");
194
195        if (async_event && testAndClearAsyncEvent()) {
196            // Take the event queue lock in case any of the service
197            // routines want to schedule new events.
198            std::lock_guard<EventQueue> lock(*eventq);
199            if (async_statdump || async_statreset) {
200                Stats::schedStatEvent(async_statdump, async_statreset);
201                async_statdump = false;
202                async_statreset = false;
203            }
204
205            if (async_io) {
206                async_io = false;
207                pollQueue.service();
208            }
209
210            if (async_exit) {
211                async_exit = false;
212                exitSimLoop("user interrupt received");
213            }
214
215            if (async_exception) {
216                async_exception = false;
217                return NULL;
218            }
219        }
220
221        Event *exit_event = eventq->serviceOne();
222        if (exit_event != NULL) {
223            return exit_event;
224        }
225    }
226
227    // not reached... only exit is return on SimLoopExitEvent
228}
229