/*
* Copyright (c) 2006 The Regents of The University of Michigan
+ * Copyright (c) 2013 Advanced Micro Devices, Inc.
+ * Copyright (c) 2013 Mark D. Hill and David A. Wood
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* Steve Reinhardt
*/
+#include <mutex>
+#include <thread>
+
#include "base/misc.hh"
#include "base/pollevent.hh"
#include "base/types.hh"
#include "sim/simulate.hh"
#include "sim/stat_control.hh"
+//! Mutex for handling async events.
+std::mutex asyncEventMutex;
+
+//! Global barrier for synchronizing threads entering/exiting the
+//! simulation loop.
+Barrier *threadBarrier;
+
+//! forward declaration
+Event *doSimLoop(EventQueue *);
+
+/**
+ * The main function for all subordinate threads (i.e., all threads
+ * other than the main thread). These threads start by waiting on
+ * threadBarrier. Once all threads have arrived at threadBarrier,
+ * they enter the simulation loop concurrently. When they exit the
+ * loop, they return to waiting on threadBarrier. This process is
+ * repeated until the simulation terminates.
+ */
+static void
+thread_loop(EventQueue *queue)
+{
+ while (true) {
+ threadBarrier->wait();
+ doSimLoop(queue);
+ }
+}
+
/** Simulate for num_cycles additional cycles. If num_cycles is -1
* (the default), do not limit simulation; some other event must
* terminate the loop. Exported to Python via SWIG.
* @return The SimLoopExitEvent that caused the loop to exit.
*/
-
-// record the clock cycle for last exit event
-Tick lastExitTick = 0;
-
-SimLoopExitEvent *
+GlobalSimLoopExitEvent *
simulate(Tick num_cycles)
{
+ // The first time simulate() is called from the Python code, we need to
+ // create a thread for each of event queues referenced by the
+ // instantiated sim objects.
+ static bool threads_initialized = false;
+ static std::vector<std::thread *> threads;
+
+ if (!threads_initialized) {
+ threadBarrier = new Barrier(numMainEventQueues);
+
+ // the main thread (the one we're currently running on)
+ // handles queue 0, so we only need to allocate new threads
+ // for queues 1..N-1. We'll call these the "subordinate" threads.
+ for (uint32_t i = 1; i < numMainEventQueues; i++) {
+ threads.push_back(new std::thread(thread_loop, mainEventQueue[i]));
+ }
+
+ threads_initialized = true;
+ }
+
inform("Entering event queue @ %d. Starting simulation...\n", curTick());
if (num_cycles < MaxTick - curTick())
else // counter would roll over or be set to MaxTick anyhow
num_cycles = MaxTick;
- Event *limit_event =
- new SimLoopExitEvent("simulate() limit reached", 0);
- mainEventQueue.schedule(limit_event, num_cycles);
+ GlobalEvent *limit_event = new GlobalSimLoopExitEvent(num_cycles,
+ "simulate() limit reached", 0, 0);
+
+ GlobalSyncEvent *quantum_event = NULL;
+ if (numMainEventQueues > 1) {
+ if (simQuantum == 0) {
+ fatal("Quantum for multi-eventq simulation not specified");
+ }
+
+ quantum_event = new GlobalSyncEvent(curTick() + simQuantum, simQuantum,
+ EventBase::Progress_Event_Pri, 0);
+
+ inParallelMode = true;
+ }
+
+ // all subordinate (created) threads should be waiting on the
+ // barrier; the arrival of the main thread here will satisfy the
+ // barrier, and all threads will enter doSimLoop in parallel
+ threadBarrier->wait();
+ Event *local_event = doSimLoop(mainEventQueue[0]);
+ assert(local_event != NULL);
+
+ inParallelMode = false;
+
+ // locate the global exit event and return it to Python
+ BaseGlobalEvent *global_event = local_event->globalEvent();
+ assert(global_event != NULL);
+
+ GlobalSimLoopExitEvent *global_exit_event =
+ dynamic_cast<GlobalSimLoopExitEvent *>(global_event);
+ assert(global_exit_event != NULL);
+
+ // if we didn't hit limit_event, delete it.
+ if (global_exit_event != limit_event) {
+ assert(limit_event->scheduled());
+ limit_event->deschedule();
+ delete limit_event;
+ }
+
+ //! Delete the simulation quantum event.
+ if (quantum_event != NULL) {
+ quantum_event->deschedule();
+ delete quantum_event;
+ }
+
+ return global_exit_event;
+}
+
+/**
+ * Test and clear the global async_event flag, such that each time the
+ * flag is cleared, only one thread returns true (and thus is assigned
+ * to handle the corresponding async event(s)).
+ */
+static bool
+testAndClearAsyncEvent()
+{
+ bool was_set = false;
+ asyncEventMutex.lock();
+
+ if (async_event) {
+ was_set = true;
+ async_event = false;
+ }
+
+ asyncEventMutex.unlock();
+ return was_set;
+}
+
+/**
+ * The main per-thread simulation loop. This loop is executed by all
+ * simulation threads (the main thread and the subordinate threads) in
+ * parallel.
+ */
+Event *
+doSimLoop(EventQueue *eventq)
+{
+ // set the per thread current eventq pointer
+ curEventQueue(eventq);
+ eventq->handleAsyncInsertions();
while (1) {
// there should always be at least one event (the SimLoopExitEvent
// we just scheduled) in the queue
- assert(!mainEventQueue.empty());
- assert(curTick() <= mainEventQueue.nextTick() &&
+ assert(!eventq->empty());
+ assert(curTick() <= eventq->nextTick() &&
"event scheduled in the past");
- Event *exit_event = mainEventQueue.serviceOne();
+ Event *exit_event = eventq->serviceOne();
if (exit_event != NULL) {
- /*
- * if there are multiple exit events in the same cycle, drain the
- * following exit events since gem5 only allows one * exit event in
- * a cycle
- */
- if (lastExitTick == curTick())
- continue;
- else
- lastExitTick = curTick();
-
- // hit some kind of exit event; return to Python
- // event must be subclass of SimLoopExitEvent...
- SimLoopExitEvent *se_event;
- se_event = dynamic_cast<SimLoopExitEvent *>(exit_event);
-
- if (se_event == NULL)
- panic("Bogus exit event class!");
-
- // if we didn't hit limit_event, delete it
- if (se_event != limit_event) {
- assert(limit_event->scheduled());
- limit_event->squash();
- hack_once("be nice to actually delete the event here");
- }
-
- return se_event;
+ return exit_event;
}
- if (async_event) {
+ if (async_event && testAndClearAsyncEvent()) {
+ // Take the event queue lock in case any of the service
+ // routines want to schedule new events.
+ std::lock_guard<EventQueue> lock(*eventq);
async_event = false;
if (async_statdump || async_statreset) {
Stats::schedStatEvent(async_statdump, async_statreset);
exitSimLoop("user interrupt received");
}
- if (async_io || async_alarm) {
+ if (async_io) {
async_io = false;
- async_alarm = false;
pollQueue.service();
}
// not reached... only exit is return on SimLoopExitEvent
}
-
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