simulate.cc revision 10762:fe0972727902 
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
74GlobalSimLoopExitEvent *simulate_limit_event = nullptr;
75
76/** Simulate for num_cycles additional cycles.  If num_cycles is -1
77 * (the default), do not limit simulation; some other event must
78 * terminate the loop.  Exported to Python via SWIG.
79 * @return The SimLoopExitEvent that caused the loop to exit.
80 */
81GlobalSimLoopExitEvent *
82simulate(Tick num_cycles)
83{
84    // The first time simulate() is called from the Python code, we need to
85    // create a thread for each of event queues referenced by the
86    // instantiated sim objects.
87    static bool threads_initialized = false;
88    static std::vector<std::thread *> threads;
89
90    if (!threads_initialized) {
91        threadBarrier = new Barrier(numMainEventQueues);
92
93        // the main thread (the one we're currently running on)
94        // handles queue 0, so we only need to allocate new threads
95        // for queues 1..N-1.  We'll call these the "subordinate" threads.
96        for (uint32_t i = 1; i < numMainEventQueues; i++) {
97            threads.push_back(new std::thread(thread_loop, mainEventQueue[i]));
98        }
99
100        threads_initialized = true;
101        simulate_limit_event =
102            new GlobalSimLoopExitEvent(mainEventQueue[0]->getCurTick(),
103                                       "simulate() limit reached", 0);
104    }
105
106    inform("Entering event queue @ %d.  Starting simulation...\n", curTick());
107
108    if (num_cycles < MaxTick - curTick())
109        num_cycles = curTick() + num_cycles;
110    else // counter would roll over or be set to MaxTick anyhow
111        num_cycles = MaxTick;
112
113    simulate_limit_event->reschedule(num_cycles);
114
115    GlobalSyncEvent *quantum_event = NULL;
116    if (numMainEventQueues > 1) {
117        if (simQuantum == 0) {
118            fatal("Quantum for multi-eventq simulation not specified");
119        }
120
121        quantum_event = new GlobalSyncEvent(curTick() + simQuantum, simQuantum,
122                            EventBase::Progress_Event_Pri, 0);
123
124        inParallelMode = true;
125    }
126
127    // all subordinate (created) threads should be waiting on the
128    // barrier; the arrival of the main thread here will satisfy the
129    // barrier, and all threads will enter doSimLoop in parallel
130    threadBarrier->wait();
131    Event *local_event = doSimLoop(mainEventQueue[0]);
132    assert(local_event != NULL);
133
134    inParallelMode = false;
135
136    // locate the global exit event and return it to Python
137    BaseGlobalEvent *global_event = local_event->globalEvent();
138    assert(global_event != NULL);
139
140    GlobalSimLoopExitEvent *global_exit_event =
141        dynamic_cast<GlobalSimLoopExitEvent *>(global_event);
142    assert(global_exit_event != NULL);
143
144    //! Delete the simulation quantum event.
145    if (quantum_event != NULL) {
146        quantum_event->deschedule();
147        delete quantum_event;
148    }
149
150    return global_exit_event;
151}
152
153/**
154 * Test and clear the global async_event flag, such that each time the
155 * flag is cleared, only one thread returns true (and thus is assigned
156 * to handle the corresponding async event(s)).
157 */
158static bool
159testAndClearAsyncEvent()
160{
161    bool was_set = false;
162    asyncEventMutex.lock();
163
164    if (async_event) {
165        was_set = true;
166        async_event = false;
167    }
168
169    asyncEventMutex.unlock();
170    return was_set;
171}
172
173/**
174 * The main per-thread simulation loop. This loop is executed by all
175 * simulation threads (the main thread and the subordinate threads) in
176 * parallel.
177 */
178Event *
179doSimLoop(EventQueue *eventq)
180{
181    // set the per thread current eventq pointer
182    curEventQueue(eventq);
183    eventq->handleAsyncInsertions();
184
185    while (1) {
186        // there should always be at least one event (the SimLoopExitEvent
187        // we just scheduled) in the queue
188        assert(!eventq->empty());
189        assert(curTick() <= eventq->nextTick() &&
190               "event scheduled in the past");
191
192        if (async_event && testAndClearAsyncEvent()) {
193            // Take the event queue lock in case any of the service
194            // routines want to schedule new events.
195            std::lock_guard<EventQueue> lock(*eventq);
196            if (async_statdump || async_statreset) {
197                Stats::schedStatEvent(async_statdump, async_statreset);
198                async_statdump = false;
199                async_statreset = false;
200            }
201
202            if (async_io) {
203                async_io = false;
204                pollQueue.service();
205            }
206
207            if (async_exit) {
208                async_exit = false;
209                exitSimLoop("user interrupt received");
210            }
211
212            if (async_exception) {
213                async_exception = false;
214                return NULL;
215            }
216        }
217
218        Event *exit_event = eventq->serviceOne();
219        if (exit_event != NULL) {
220            return exit_event;
221        }
222    }
223
224    // not reached... only exit is return on SimLoopExitEvent
225}
226