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/*
* Copyright (c) 2015-2016 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Gabor Dozsa
*/
/* @file
* The interface class for dist-gem5 simulations.
*/
#include "dev/net/dist_iface.hh"
#include <queue>
#include <thread>
#include "base/random.hh"
#include "base/trace.hh"
#include "cpu/thread_context.hh"
#include "debug/DistEthernet.hh"
#include "debug/DistEthernetPkt.hh"
#include "dev/net/etherpkt.hh"
#include "sim/sim_exit.hh"
#include "sim/sim_object.hh"
#include "sim/system.hh"
using namespace std;
DistIface::Sync *DistIface::sync = nullptr;
System *DistIface::sys = nullptr;
DistIface::SyncEvent *DistIface::syncEvent = nullptr;
unsigned DistIface::distIfaceNum = 0;
unsigned DistIface::recvThreadsNum = 0;
DistIface *DistIface::master = nullptr;
bool DistIface::isSwitch = false;
void
DistIface::Sync::init(Tick start_tick, Tick repeat_tick)
{
if (start_tick < nextAt) {
nextAt = start_tick;
inform("Next dist synchronisation tick is changed to %lu.\n", nextAt);
}
if (repeat_tick == 0)
panic("Dist synchronisation interval must be greater than zero");
if (repeat_tick < nextRepeat) {
nextRepeat = repeat_tick;
inform("Dist synchronisation interval is changed to %lu.\n",
nextRepeat);
}
}
void
DistIface::Sync::abort()
{
std::unique_lock<std::mutex> sync_lock(lock);
waitNum = 0;
isAbort = true;
sync_lock.unlock();
cv.notify_one();
}
DistIface::SyncSwitch::SyncSwitch(int num_nodes)
{
numNodes = num_nodes;
waitNum = num_nodes;
numExitReq = 0;
numCkptReq = 0;
numStopSyncReq = 0;
doExit = false;
doCkpt = false;
doStopSync = false;
nextAt = std::numeric_limits<Tick>::max();
nextRepeat = std::numeric_limits<Tick>::max();
isAbort = false;
}
DistIface::SyncNode::SyncNode()
{
waitNum = 0;
needExit = ReqType::none;
needCkpt = ReqType::none;
needStopSync = ReqType::none;
doExit = false;
doCkpt = false;
doStopSync = false;
nextAt = std::numeric_limits<Tick>::max();
nextRepeat = std::numeric_limits<Tick>::max();
isAbort = false;
}
bool
DistIface::SyncNode::run(bool same_tick)
{
std::unique_lock<std::mutex> sync_lock(lock);
Header header;
assert(waitNum == 0);
assert(!isAbort);
waitNum = DistIface::recvThreadsNum;
// initiate the global synchronisation
header.msgType = MsgType::cmdSyncReq;
header.sendTick = curTick();
header.syncRepeat = nextRepeat;
header.needCkpt = needCkpt;
header.needStopSync = needStopSync;
if (needCkpt != ReqType::none)
needCkpt = ReqType::pending;
header.needExit = needExit;
if (needExit != ReqType::none)
needExit = ReqType::pending;
if (needStopSync != ReqType::none)
needStopSync = ReqType::pending;
DistIface::master->sendCmd(header);
// now wait until all receiver threads complete the synchronisation
auto lf = [this]{ return waitNum == 0; };
cv.wait(sync_lock, lf);
// global synchronisation is done.
assert(isAbort || !same_tick || (nextAt == curTick()));
return !isAbort;
}
bool
DistIface::SyncSwitch::run(bool same_tick)
{
std::unique_lock<std::mutex> sync_lock(lock);
Header header;
// Wait for the sync requests from the nodes
if (waitNum > 0) {
auto lf = [this]{ return waitNum == 0; };
cv.wait(sync_lock, lf);
}
assert(waitNum == 0);
if (isAbort) // sync aborted
return false;
assert(!same_tick || (nextAt == curTick()));
waitNum = numNodes;
// Complete the global synchronisation
header.msgType = MsgType::cmdSyncAck;
header.sendTick = nextAt;
header.syncRepeat = nextRepeat;
if (doCkpt || numCkptReq == numNodes) {
doCkpt = true;
header.needCkpt = ReqType::immediate;
numCkptReq = 0;
} else {
header.needCkpt = ReqType::none;
}
if (doExit || numExitReq == numNodes) {
doExit = true;
header.needExit = ReqType::immediate;
} else {
header.needExit = ReqType::none;
}
if (doStopSync || numStopSyncReq == numNodes) {
doStopSync = true;
numStopSyncReq = 0;
header.needStopSync = ReqType::immediate;
} else {
header.needStopSync = ReqType::none;
}
DistIface::master->sendCmd(header);
return true;
}
bool
DistIface::SyncSwitch::progress(Tick send_tick,
Tick sync_repeat,
ReqType need_ckpt,
ReqType need_exit,
ReqType need_stop_sync)
{
std::unique_lock<std::mutex> sync_lock(lock);
if (isAbort) // sync aborted
return false;
assert(waitNum > 0);
if (send_tick > nextAt)
nextAt = send_tick;
if (nextRepeat > sync_repeat)
nextRepeat = sync_repeat;
if (need_ckpt == ReqType::collective)
numCkptReq++;
else if (need_ckpt == ReqType::immediate)
doCkpt = true;
if (need_exit == ReqType::collective)
numExitReq++;
else if (need_exit == ReqType::immediate)
doExit = true;
if (need_stop_sync == ReqType::collective)
numStopSyncReq++;
else if (need_stop_sync == ReqType::immediate)
doStopSync = true;
waitNum--;
// Notify the simulation thread if the on-going sync is complete
if (waitNum == 0) {
sync_lock.unlock();
cv.notify_one();
}
// The receive thread must keep alive in the switch until the node
// closes the connection. Thus, we always return true here.
return true;
}
bool
DistIface::SyncNode::progress(Tick max_send_tick,
Tick next_repeat,
ReqType do_ckpt,
ReqType do_exit,
ReqType do_stop_sync)
{
std::unique_lock<std::mutex> sync_lock(lock);
if (isAbort) // sync aborted
return false;
assert(waitNum > 0);
nextAt = max_send_tick;
nextRepeat = next_repeat;
doCkpt = (do_ckpt != ReqType::none);
doExit = (do_exit != ReqType::none);
doStopSync = (do_stop_sync != ReqType::none);
waitNum--;
// Notify the simulation thread if the on-going sync is complete
if (waitNum == 0) {
sync_lock.unlock();
cv.notify_one();
}
// The receive thread must finish when simulation is about to exit
return !doExit;
}
void
DistIface::SyncNode::requestCkpt(ReqType req)
{
std::lock_guard<std::mutex> sync_lock(lock);
assert(req != ReqType::none);
if (needCkpt != ReqType::none)
warn("Ckpt requested multiple times (req:%d)\n", static_cast<int>(req));
if (needCkpt == ReqType::none || req == ReqType::immediate)
needCkpt = req;
}
void
DistIface::SyncNode::requestExit(ReqType req)
{
std::lock_guard<std::mutex> sync_lock(lock);
assert(req != ReqType::none);
if (needExit != ReqType::none)
warn("Exit requested multiple times (req:%d)\n", static_cast<int>(req));
if (needExit == ReqType::none || req == ReqType::immediate)
needExit = req;
}
void
DistIface::Sync::drainComplete()
{
if (doCkpt) {
// The first DistIface object called this right before writing the
// checkpoint. We need to drain the underlying physical network here.
// Note that other gem5 peers may enter this barrier at different
// ticks due to draining.
run(false);
// Only the "first" DistIface object has to perform the sync
doCkpt = false;
}
}
void
DistIface::SyncNode::serialize(CheckpointOut &cp) const
{
int need_exit = static_cast<int>(needExit);
SERIALIZE_SCALAR(need_exit);
}
void
DistIface::SyncNode::unserialize(CheckpointIn &cp)
{
int need_exit;
UNSERIALIZE_SCALAR(need_exit);
needExit = static_cast<ReqType>(need_exit);
}
void
DistIface::SyncSwitch::serialize(CheckpointOut &cp) const
{
SERIALIZE_SCALAR(numExitReq);
}
void
DistIface::SyncSwitch::unserialize(CheckpointIn &cp)
{
UNSERIALIZE_SCALAR(numExitReq);
}
void
DistIface::SyncEvent::start()
{
// Note that this may be called either from startup() or drainResume()
// At this point, all DistIface objects has already called Sync::init() so
// we have a local minimum of the start tick and repeat for the periodic
// sync.
repeat = DistIface::sync->nextRepeat;
// Do a global barrier to agree on a common repeat value (the smallest
// one from all participating nodes.
if (!DistIface::sync->run(false))
panic("DistIface::SyncEvent::start() aborted\n");
assert(!DistIface::sync->doCkpt);
assert(!DistIface::sync->doExit);
assert(!DistIface::sync->doStopSync);
assert(DistIface::sync->nextAt >= curTick());
assert(DistIface::sync->nextRepeat <= repeat);
if (curTick() == 0)
assert(!scheduled());
// Use the maximum of the current tick for all participating nodes or a
// user provided starting tick.
if (scheduled())
reschedule(DistIface::sync->nextAt);
else
schedule(DistIface::sync->nextAt);
inform("Dist sync scheduled at %lu and repeats %lu\n", when(),
DistIface::sync->nextRepeat);
}
void
DistIface::SyncEvent::process()
{
// We may not start a global periodic sync while draining before taking a
// checkpoint. This is due to the possibility that peer gem5 processes
// may not hit the same periodic sync before they complete draining and
// that would make this periodic sync clash with sync called from
// DistIface::serialize() by other gem5 processes.
// We would need a 'distributed drain' solution to eliminate this
// restriction.
// Note that if draining was not triggered by checkpointing then we are
// fine since no extra global sync will happen (i.e. all peer gem5 will
// hit this periodic sync eventually).
panic_if(_draining && DistIface::sync->doCkpt,
"Distributed sync is hit while draining");
/*
* Note that this is a global event so this process method will be called
* by only exactly one thread.
*/
/*
* We hold the eventq lock at this point but the receiver thread may
* need the lock to schedule new recv events while waiting for the
* dist sync to complete.
* Note that the other simulation threads also release their eventq
* locks while waiting for us due to the global event semantics.
*/
{
EventQueue::ScopedRelease sr(curEventQueue());
// we do a global sync here that is supposed to happen at the same
// tick in all gem5 peers
if (!DistIface::sync->run(true))
return; // global sync aborted
// global sync completed
}
if (DistIface::sync->doCkpt)
exitSimLoop("checkpoint");
if (DistIface::sync->doExit) {
exitSimLoop("exit request from gem5 peers");
return;
}
if (DistIface::sync->doStopSync) {
DistIface::sync->doStopSync = false;
inform("synchronization disabled at %lu\n", curTick());
// The switch node needs to wait for the next sync immediately.
if (DistIface::isSwitch) {
start();
} else {
// Wake up thread contexts on non-switch nodes.
for (int i = 0; i < DistIface::master->sys->numContexts(); i++) {
ThreadContext *tc =
DistIface::master->sys->getThreadContext(i);
if (tc->status() == ThreadContext::Suspended)
tc->activate();
else
warn_once("Tried to wake up thread in dist-gem5, but it "
"was already awake!\n");
}
}
return;
}
// schedule the next periodic sync
repeat = DistIface::sync->nextRepeat;
schedule(curTick() + repeat);
}
void
DistIface::RecvScheduler::init(Event *recv_done, Tick link_delay)
{
// This is called from the receiver thread when it starts running. The new
// receiver thread shares the event queue with the simulation thread
// (associated with the simulated Ethernet link).
curEventQueue(eventManager->eventQueue());
recvDone = recv_done;
linkDelay = link_delay;
}
Tick
DistIface::RecvScheduler::calcReceiveTick(Tick send_tick,
Tick send_delay,
Tick prev_recv_tick)
{
Tick recv_tick = send_tick + send_delay + linkDelay;
// sanity check (we need atleast a send delay long window)
assert(recv_tick >= prev_recv_tick + send_delay);
panic_if(prev_recv_tick + send_delay > recv_tick,
"Receive window is smaller than send delay");
panic_if(recv_tick <= curTick(),
"Simulators out of sync - missed packet receive by %llu ticks"
"(rev_recv_tick: %lu send_tick: %lu send_delay: %lu "
"linkDelay: %lu )",
curTick() - recv_tick, prev_recv_tick, send_tick, send_delay,
linkDelay);
return recv_tick;
}
void
DistIface::RecvScheduler::resumeRecvTicks()
{
// Schedule pending packets asap in case link speed/delay changed when
// restoring from the checkpoint.
// This may be done during unserialize except that curTick() is unknown
// so we call this during drainResume().
// If we are not restoring from a checkppint then link latency could not
// change so we just return.
if (!ckptRestore)
return;
std::vector<Desc> v;
while (!descQueue.empty()) {
Desc d = descQueue.front();
descQueue.pop();
d.sendTick = curTick();
d.sendDelay = d.packet->simLength; // assume 1 tick/byte max link speed
v.push_back(d);
}
for (auto &d : v)
descQueue.push(d);
if (recvDone->scheduled()) {
assert(!descQueue.empty());
eventManager->reschedule(recvDone, curTick());
} else {
assert(descQueue.empty() && v.empty());
}
ckptRestore = false;
}
void
DistIface::RecvScheduler::pushPacket(EthPacketPtr new_packet,
Tick send_tick,
Tick send_delay)
{
// Note : this is called from the receiver thread
curEventQueue()->lock();
Tick recv_tick = calcReceiveTick(send_tick, send_delay, prevRecvTick);
DPRINTF(DistEthernetPkt, "DistIface::recvScheduler::pushPacket "
"send_tick:%llu send_delay:%llu link_delay:%llu recv_tick:%llu\n",
send_tick, send_delay, linkDelay, recv_tick);
// Every packet must be sent and arrive in the same quantum
assert(send_tick > master->syncEvent->when() -
master->syncEvent->repeat);
// No packet may be scheduled for receive in the arrival quantum
assert(send_tick + send_delay + linkDelay > master->syncEvent->when());
// Now we are about to schedule a recvDone event for the new data packet.
// We use the same recvDone object for all incoming data packets. Packet
// descriptors are saved in the ordered queue. The currently scheduled
// packet is always on the top of the queue.
// NOTE: we use the event queue lock to protect the receive desc queue,
// too, which is accessed both by the receiver thread and the simulation
// thread.
descQueue.emplace(new_packet, send_tick, send_delay);
if (descQueue.size() == 1) {
assert(!recvDone->scheduled());
eventManager->schedule(recvDone, recv_tick);
} else {
assert(recvDone->scheduled());
panic_if(descQueue.front().sendTick + descQueue.front().sendDelay > recv_tick,
"Out of order packet received (recv_tick: %lu top(): %lu\n",
recv_tick, descQueue.front().sendTick + descQueue.front().sendDelay);
}
curEventQueue()->unlock();
}
EthPacketPtr
DistIface::RecvScheduler::popPacket()
{
// Note : this is called from the simulation thread when a receive done
// event is being processed for the link. We assume that the thread holds
// the event queue queue lock when this is called!
EthPacketPtr next_packet = descQueue.front().packet;
descQueue.pop();
if (descQueue.size() > 0) {
Tick recv_tick = calcReceiveTick(descQueue.front().sendTick,
descQueue.front().sendDelay,
curTick());
eventManager->schedule(recvDone, recv_tick);
}
prevRecvTick = curTick();
return next_packet;
}
void
DistIface::RecvScheduler::Desc::serialize(CheckpointOut &cp) const
{
SERIALIZE_SCALAR(sendTick);
SERIALIZE_SCALAR(sendDelay);
packet->serialize("rxPacket", cp);
}
void
DistIface::RecvScheduler::Desc::unserialize(CheckpointIn &cp)
{
UNSERIALIZE_SCALAR(sendTick);
UNSERIALIZE_SCALAR(sendDelay);
packet = std::make_shared<EthPacketData>();
packet->unserialize("rxPacket", cp);
}
void
DistIface::RecvScheduler::serialize(CheckpointOut &cp) const
{
SERIALIZE_SCALAR(prevRecvTick);
// serialize the receive desc queue
std::queue<Desc> tmp_queue(descQueue);
unsigned n_desc_queue = descQueue.size();
assert(tmp_queue.size() == descQueue.size());
SERIALIZE_SCALAR(n_desc_queue);
for (int i = 0; i < n_desc_queue; i++) {
tmp_queue.front().serializeSection(cp, csprintf("rxDesc_%d", i));
tmp_queue.pop();
}
assert(tmp_queue.empty());
}
void
DistIface::RecvScheduler::unserialize(CheckpointIn &cp)
{
assert(descQueue.size() == 0);
assert(!recvDone->scheduled());
assert(!ckptRestore);
UNSERIALIZE_SCALAR(prevRecvTick);
// unserialize the receive desc queue
unsigned n_desc_queue;
UNSERIALIZE_SCALAR(n_desc_queue);
for (int i = 0; i < n_desc_queue; i++) {
Desc recv_desc;
recv_desc.unserializeSection(cp, csprintf("rxDesc_%d", i));
descQueue.push(recv_desc);
}
ckptRestore = true;
}
DistIface::DistIface(unsigned dist_rank,
unsigned dist_size,
Tick sync_start,
Tick sync_repeat,
EventManager *em,
bool use_pseudo_op,
bool is_switch, int num_nodes) :
syncStart(sync_start), syncRepeat(sync_repeat),
recvThread(nullptr), recvScheduler(em), syncStartOnPseudoOp(use_pseudo_op),
rank(dist_rank), size(dist_size)
{
DPRINTF(DistEthernet, "DistIface() ctor rank:%d\n",dist_rank);
isMaster = false;
if (master == nullptr) {
assert(sync == nullptr);
assert(syncEvent == nullptr);
isSwitch = is_switch;
if (is_switch)
sync = new SyncSwitch(num_nodes);
else
sync = new SyncNode();
syncEvent = new SyncEvent();
master = this;
isMaster = true;
}
distIfaceId = distIfaceNum;
distIfaceNum++;
}
DistIface::~DistIface()
{
assert(recvThread);
recvThread->join();
delete recvThread;
if (distIfaceNum-- == 0) {
assert(syncEvent);
delete syncEvent;
assert(sync);
delete sync;
}
if (this == master)
master = nullptr;
}
void
DistIface::packetOut(EthPacketPtr pkt, Tick send_delay)
{
Header header;
// Prepare a dist header packet for the Ethernet packet we want to
// send out.
header.msgType = MsgType::dataDescriptor;
header.sendTick = curTick();
header.sendDelay = send_delay;
header.dataPacketLength = pkt->length;
header.simLength = pkt->simLength;
// Send out the packet and the meta info.
sendPacket(header, pkt);
DPRINTF(DistEthernetPkt,
"DistIface::sendDataPacket() done size:%d send_delay:%llu\n",
pkt->length, send_delay);
}
void
DistIface::recvThreadFunc(Event *recv_done, Tick link_delay)
{
EthPacketPtr new_packet;
DistHeaderPkt::Header header;
// Initialize receive scheduler parameters
recvScheduler.init(recv_done, link_delay);
// Main loop to wait for and process any incoming message.
for (;;) {
// recvHeader() blocks until the next dist header packet comes in.
if (!recvHeader(header)) {
// We lost connection to the peer gem5 processes most likely
// because one of them called m5 exit. So we stop here.
// Grab the eventq lock to stop the simulation thread
curEventQueue()->lock();
exitSimLoop("connection to gem5 peer got closed");
curEventQueue()->unlock();
// The simulation thread may be blocked in processing an on-going
// global synchronisation. Abort the sync to give the simulation
// thread a chance to make progress and process the exit event.
sync->abort();
// Finish receiver thread
break;
}
// We got a valid dist header packet, let's process it
if (header.msgType == MsgType::dataDescriptor) {
recvPacket(header, new_packet);
recvScheduler.pushPacket(new_packet,
header.sendTick,
header.sendDelay);
} else {
// everything else must be synchronisation related command
if (!sync->progress(header.sendTick,
header.syncRepeat,
header.needCkpt,
header.needExit,
header.needStopSync))
// Finish receiver thread if simulation is about to exit
break;
}
}
}
void
DistIface::spawnRecvThread(const Event *recv_done, Tick link_delay)
{
assert(recvThread == nullptr);
recvThread = new std::thread(&DistIface::recvThreadFunc,
this,
const_cast<Event *>(recv_done),
link_delay);
recvThreadsNum++;
}
DrainState
DistIface::drain()
{
DPRINTF(DistEthernet,"DistIFace::drain() called\n");
// This can be called multiple times in the same drain cycle.
if (this == master)
syncEvent->draining(true);
return DrainState::Drained;
}
void
DistIface::drainResume() {
DPRINTF(DistEthernet,"DistIFace::drainResume() called\n");
if (this == master)
syncEvent->draining(false);
recvScheduler.resumeRecvTicks();
}
void
DistIface::serialize(CheckpointOut &cp) const
{
// Drain the dist interface before the checkpoint is taken. We cannot call
// this as part of the normal drain cycle because this dist sync has to be
// called exactly once after the system is fully drained.
sync->drainComplete();
unsigned rank_orig = rank, dist_iface_id_orig = distIfaceId;
SERIALIZE_SCALAR(rank_orig);
SERIALIZE_SCALAR(dist_iface_id_orig);
recvScheduler.serializeSection(cp, "recvScheduler");
if (this == master) {
sync->serializeSection(cp, "Sync");
}
}
void
DistIface::unserialize(CheckpointIn &cp)
{
unsigned rank_orig, dist_iface_id_orig;
UNSERIALIZE_SCALAR(rank_orig);
UNSERIALIZE_SCALAR(dist_iface_id_orig);
panic_if(rank != rank_orig, "Rank mismatch at resume (rank=%d, orig=%d)",
rank, rank_orig);
panic_if(distIfaceId != dist_iface_id_orig, "Dist iface ID mismatch "
"at resume (distIfaceId=%d, orig=%d)", distIfaceId,
dist_iface_id_orig);
recvScheduler.unserializeSection(cp, "recvScheduler");
if (this == master) {
sync->unserializeSection(cp, "Sync");
}
}
void
DistIface::init(const Event *done_event, Tick link_delay)
{
// Init hook for the underlaying message transport to setup/finalize
// communication channels
initTransport();
// Spawn a new receiver thread that will process messages
// coming in from peer gem5 processes.
// The receive thread will also schedule a (receive) doneEvent
// for each incoming data packet.
spawnRecvThread(done_event, link_delay);
// Adjust the periodic sync start and interval. Different DistIface
// might have different requirements. The singleton sync object
// will select the minimum values for both params.
assert(sync != nullptr);
sync->init(syncStart, syncRepeat);
// Initialize the seed for random generator to avoid the same sequence
// in all gem5 peer processes
assert(master != nullptr);
if (this == master)
random_mt.init(5489 * (rank+1) + 257);
}
void
DistIface::startup()
{
DPRINTF(DistEthernet, "DistIface::startup() started\n");
// Schedule synchronization unless we are not a switch in pseudo_op mode.
if (this == master && (!syncStartOnPseudoOp || isSwitch))
syncEvent->start();
DPRINTF(DistEthernet, "DistIface::startup() done\n");
}
bool
DistIface::readyToCkpt(Tick delay, Tick period)
{
bool ret = true;
DPRINTF(DistEthernet, "DistIface::readyToCkpt() called, delay:%lu "
"period:%lu\n", delay, period);
if (master) {
if (delay == 0) {
inform("m5 checkpoint called with zero delay => triggering collaborative "
"checkpoint\n");
sync->requestCkpt(ReqType::collective);
} else {
inform("m5 checkpoint called with non-zero delay => triggering immediate "
"checkpoint (at the next sync)\n");
sync->requestCkpt(ReqType::immediate);
}
if (period != 0)
inform("Non-zero period for m5_ckpt is ignored in "
"distributed gem5 runs\n");
ret = false;
}
return ret;
}
void
DistIface::SyncNode::requestStopSync(ReqType req)
{
std::lock_guard<std::mutex> sync_lock(lock);
needStopSync = req;
}
void
DistIface::toggleSync(ThreadContext *tc)
{
// Unforunate that we have to populate the system pointer member this way.
master->sys = tc->getSystemPtr();
// The invariant for both syncing and "unsyncing" is that all threads will
// stop executing intructions until the desired sync state has been reached
// for all nodes. This is the easiest way to prevent deadlock (in the case
// of "unsyncing") and causality errors (in the case of syncing).
if (master->syncEvent->scheduled()) {
inform("Request toggling syncronization off\n");
master->sync->requestStopSync(ReqType::collective);
// At this point, we have no clue when everyone will reach the sync
// stop point. Suspend execution of all local thread contexts.
// Dist-gem5 will reactivate all thread contexts when everyone has
// reached the sync stop point.
for (int i = 0; i < master->sys->numContexts(); i++) {
ThreadContext *tc = master->sys->getThreadContext(i);
if (tc->status() == ThreadContext::Active)
tc->quiesce();
}
} else {
inform("Request toggling syncronization on\n");
master->syncEvent->start();
// We need to suspend all CPUs until the sync point is reached by all
// nodes to prevent causality errors. We can also schedule CPU
// activation here, since we know exactly when the next sync will
// occur.
for (int i = 0; i < master->sys->numContexts(); i++) {
ThreadContext *tc = master->sys->getThreadContext(i);
if (tc->status() == ThreadContext::Active)
tc->quiesceTick(master->syncEvent->when() + 1);
}
}
}
bool
DistIface::readyToExit(Tick delay)
{
bool ret = true;
DPRINTF(DistEthernet, "DistIface::readyToExit() called, delay:%lu\n",
delay);
if (master) {
// To successfully coordinate an exit, all nodes must be synchronising
if (!master->syncEvent->scheduled())
master->syncEvent->start();
if (delay == 0) {
inform("m5 exit called with zero delay => triggering collaborative "
"exit\n");
sync->requestExit(ReqType::collective);
} else {
inform("m5 exit called with non-zero delay => triggering immediate "
"exit (at the next sync)\n");
sync->requestExit(ReqType::immediate);
}
ret = false;
}
return ret;
}
uint64_t
DistIface::rankParam()
{
uint64_t val;
if (master) {
val = master->rank;
} else {
warn("Dist-rank parameter is queried in single gem5 simulation.");
val = 0;
}
return val;
}
uint64_t
DistIface::sizeParam()
{
uint64_t val;
if (master) {
val = master->size;
} else {
warn("Dist-size parameter is queried in single gem5 simulation.");
val = 1;
}
return val;
}