simulate.cc revision 10153 
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
74/** Simulate for num_cycles additional cycles.  If num_cycles is -1
75 * (the default), do not limit simulation; some other event must
76 * terminate the loop.  Exported to Python via SWIG.
77 * @return The SimLoopExitEvent that caused the loop to exit.
78 */
79GlobalSimLoopExitEvent *
80simulate(Tick num_cycles)
81{
82    // The first time simulate() is called from the Python code, we need to
83    // create a thread for each of event queues referenced by the
84    // instantiated sim objects.
85    static bool threads_initialized = false;
86    static std::vector<std::thread *> threads;
87
88    if (!threads_initialized) {
89        threadBarrier = new Barrier(numMainEventQueues);
90
91        // the main thread (the one we're currently running on)
92        // handles queue 0, so we only need to allocate new threads
93        // for queues 1..N-1.  We'll call these the "subordinate" threads.
94        for (uint32_t i = 1; i < numMainEventQueues; i++) {
95            threads.push_back(new std::thread(thread_loop, mainEventQueue[i]));
96        }
97
98        threads_initialized = true;
99    }
100
101    inform("Entering event queue @ %d.  Starting simulation...\n", curTick());
102
103    if (num_cycles < MaxTick - curTick())
104        num_cycles = curTick() + num_cycles;
105    else // counter would roll over or be set to MaxTick anyhow
106        num_cycles = MaxTick;
107
108    GlobalEvent *limit_event = new GlobalSimLoopExitEvent(num_cycles,
109                                "simulate() limit reached", 0, 0);
110
111    GlobalSyncEvent *quantum_event = NULL;
112    if (numMainEventQueues > 1) {
113        if (simQuantum == 0) {
114            fatal("Quantum for multi-eventq simulation not specified");
115        }
116
117        quantum_event = new GlobalSyncEvent(curTick() + simQuantum, simQuantum,
118                            EventBase::Progress_Event_Pri, 0);
119
120        inParallelMode = true;
121    }
122
123    // all subordinate (created) threads should be waiting on the
124    // barrier; the arrival of the main thread here will satisfy the
125    // barrier, and all threads will enter doSimLoop in parallel
126    threadBarrier->wait();
127    Event *local_event = doSimLoop(mainEventQueue[0]);
128    assert(local_event != NULL);
129
130    inParallelMode = false;
131
132    // locate the global exit event and return it to Python
133    BaseGlobalEvent *global_event = local_event->globalEvent();
134    assert(global_event != NULL);
135
136    GlobalSimLoopExitEvent *global_exit_event =
137        dynamic_cast<GlobalSimLoopExitEvent *>(global_event);
138    assert(global_exit_event != NULL);
139
140    // if we didn't hit limit_event, delete it.
141    if (global_exit_event != limit_event) {
142        assert(limit_event->scheduled());
143        limit_event->deschedule();
144        delete limit_event;
145    }
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        Event *exit_event = eventq->serviceOne();
196        if (exit_event != NULL) {
197            return exit_event;
198        }
199
200        if (async_event && testAndClearAsyncEvent()) {
201            // Take the event queue lock in case any of the service
202            // routines want to schedule new events.
203            std::lock_guard<EventQueue> lock(*eventq);
204            async_event = false;
205            if (async_statdump || async_statreset) {
206                Stats::schedStatEvent(async_statdump, async_statreset);
207                async_statdump = false;
208                async_statreset = false;
209            }
210
211            if (async_exit) {
212                async_exit = false;
213                exitSimLoop("user interrupt received");
214            }
215
216            if (async_io) {
217                async_io = false;
218                pollQueue.service();
219            }
220
221            if (async_exception) {
222                async_exception = false;
223                return NULL;
224            }
225        }
226    }
227
228    // not reached... only exit is return on SimLoopExitEvent
229}
230