gem5  v20.1.0.0
Classes | Public Member Functions | Protected Member Functions | Protected Attributes | Static Protected Attributes | List of all members
TraceCPU Class Reference

The trace cpu replays traces generated using the elastic trace probe attached to the O3 CPU model. More...

#include <trace_cpu.hh>

Inheritance diagram for TraceCPU:
BaseCPU

Classes

class  DcachePort
 DcachePort class that interfaces with L1 Data Cache. More...
 
class  ElasticDataGen
 The elastic data memory request generator to read protobuf trace containing execution trace annotated with data and ordering dependencies. More...
 
class  FixedRetryGen
 Generator to read protobuf trace containing memory requests at fixed timestamps, perform flow control and issue memory requests. More...
 
class  IcachePort
 IcachePort class that interfaces with L1 Instruction Cache. More...
 
struct  TraceStats
 

Public Member Functions

 TraceCPU (TraceCPUParams *params)
 
 ~TraceCPU ()
 
void init ()
 
Counter totalInsts () const
 This is a pure virtual function in BaseCPU. More...
 
Counter totalOps () const
 Return totalOps as the number of committed micro-ops plus the speculatively issued loads that are modelled in the TraceCPU replay. More...
 
void updateNumOps (uint64_t rob_num)
 
void wakeup (ThreadID tid=0)
 
void takeOverFrom (BaseCPU *oldCPU)
 Load the state of a CPU from the previous CPU object, invoked on all new CPUs that are about to be switched in. More...
 
void icacheRetryRecvd ()
 When instruction cache port receives a retry, schedule event icacheNextEvent. More...
 
void dcacheRetryRecvd ()
 When data cache port receives a retry, schedule event dcacheNextEvent. More...
 
void dcacheRecvTimingResp (PacketPtr pkt)
 When data cache port receives a response, this calls the dcache generator method handle to complete the load writeback. More...
 
void schedDcacheNextEvent (Tick when)
 Schedule event dcacheNextEvent at the given tick. More...
 
PortgetInstPort ()
 Used to get a reference to the icache port. More...
 
PortgetDataPort ()
 Used to get a reference to the dcache port. More...
 
- Public Member Functions inherited from BaseCPU
virtual PortProxy::SendFunctionalFunc getSendFunctional ()
 Returns a sendFunctional delegate for use with port proxies. More...
 
int cpuId () const
 Reads this CPU's ID. More...
 
uint32_t socketId () const
 Reads this CPU's Socket ID. More...
 
RequestorID dataRequestorId () const
 Reads this CPU's unique data requestor ID. More...
 
RequestorID instRequestorId () const
 Reads this CPU's unique instruction requestor ID. More...
 
PortgetPort (const std::string &if_name, PortID idx=InvalidPortID) override
 Get a port on this CPU. More...
 
uint32_t taskId () const
 Get cpu task id. More...
 
void taskId (uint32_t id)
 Set cpu task id. More...
 
uint32_t getPid () const
 
void setPid (uint32_t pid)
 
void workItemBegin ()
 
void workItemEnd ()
 
Tick instCount ()
 
BaseInterruptsgetInterruptController (ThreadID tid)
 
void postInterrupt (ThreadID tid, int int_num, int index)
 
void clearInterrupt (ThreadID tid, int int_num, int index)
 
void clearInterrupts (ThreadID tid)
 
bool checkInterrupts (ThreadID tid) const
 
Trace::InstTracergetTracer ()
 Provide access to the tracer pointer. More...
 
virtual void activateContext (ThreadID thread_num)
 Notify the CPU that the indicated context is now active. More...
 
virtual void suspendContext (ThreadID thread_num)
 Notify the CPU that the indicated context is now suspended. More...
 
virtual void haltContext (ThreadID thread_num)
 Notify the CPU that the indicated context is now halted. More...
 
int findContext (ThreadContext *tc)
 Given a Thread Context pointer return the thread num. More...
 
virtual ThreadContextgetContext (int tn)
 Given a thread num get tho thread context for it. More...
 
unsigned numContexts ()
 Get the number of thread contexts available. More...
 
ThreadID contextToThread (ContextID cid)
 Convert ContextID to threadID. More...
 
const Paramsparams () const
 
 BaseCPU (Params *params, bool is_checker=false)
 
virtual ~BaseCPU ()
 
void init () override
 
void startup () override
 
void regStats () override
 
void regProbePoints () override
 
void registerThreadContexts ()
 
void deschedulePowerGatingEvent ()
 
void schedulePowerGatingEvent ()
 
virtual void switchOut ()
 Prepare for another CPU to take over execution. More...
 
void flushTLBs ()
 Flush all TLBs in the CPU. More...
 
bool switchedOut () const
 Determine if the CPU is switched out. More...
 
virtual void verifyMemoryMode () const
 Verify that the system is in a memory mode supported by the CPU. More...
 
unsigned int cacheLineSize () const
 Get the cache line size of the system. More...
 
void serialize (CheckpointOut &cp) const override
 Serialize this object to the given output stream. More...
 
void unserialize (CheckpointIn &cp) override
 Reconstruct the state of this object from a checkpoint. More...
 
virtual void serializeThread (CheckpointOut &cp, ThreadID tid) const
 Serialize a single thread. More...
 
virtual void unserializeThread (CheckpointIn &cp, ThreadID tid)
 Unserialize one thread. More...
 
void scheduleInstStop (ThreadID tid, Counter insts, const char *cause)
 Schedule an event that exits the simulation loops after a predefined number of instructions. More...
 
uint64_t getCurrentInstCount (ThreadID tid)
 Get the number of instructions executed by the specified thread on this CPU. More...
 
void traceFunctions (Addr pc)
 
void armMonitor (ThreadID tid, Addr address)
 
bool mwait (ThreadID tid, PacketPtr pkt)
 
void mwaitAtomic (ThreadID tid, ThreadContext *tc, BaseTLB *dtb)
 
AddressMonitorgetCpuAddrMonitor (ThreadID tid)
 
bool waitForRemoteGDB () const
 
virtual void probeInstCommit (const StaticInstPtr &inst, Addr pc)
 Helper method to trigger PMU probes for a committed instruction. More...
 

Protected Member Functions

void schedIcacheNext ()
 This is the control flow that uses the functionality of the icacheGen to replay the trace. More...
 
void schedDcacheNext ()
 This is the control flow that uses the functionality of the dcacheGen to replay the trace. More...
 
void checkAndSchedExitEvent ()
 This is called when either generator finishes executing from the trace. More...
 
- Protected Member Functions inherited from BaseCPU
void updateCycleCounters (CPUState state)
 base method keeping track of cycle progression More...
 
void enterPwrGating ()
 
ProbePoints::PMUUPtr pmuProbePoint (const char *name)
 Helper method to instantiate probe points belonging to this object. More...
 

Protected Attributes

IcachePort icachePort
 Port to connect to L1 instruction cache. More...
 
DcachePort dcachePort
 Port to connect to L1 data cache. More...
 
const RequestorID instRequestorID
 Requestor id for instruction read requests. More...
 
const RequestorID dataRequestorID
 Requestor id for data read and write requests. More...
 
std::string instTraceFile
 File names for input instruction and data traces. More...
 
std::string dataTraceFile
 
FixedRetryGen icacheGen
 Instance of FixedRetryGen to replay instruction read requests. More...
 
ElasticDataGen dcacheGen
 Instance of ElasticDataGen to replay data read and write requests. More...
 
EventFunctionWrapper icacheNextEvent
 Event for the control flow method schedIcacheNext() More...
 
EventFunctionWrapper dcacheNextEvent
 Event for the control flow method schedDcacheNext() More...
 
bool oneTraceComplete
 Set to true when one of the generators finishes replaying its trace. More...
 
Tick traceOffset
 This stores the time offset in the trace, which is taken away from the ready times of requests. More...
 
CountedExitEventexecCompleteEvent
 A CountedExitEvent which when serviced decrements the counter. More...
 
const bool enableEarlyExit
 Exit when any one Trace CPU completes its execution. More...
 
const uint64_t progressMsgInterval
 Interval of committed instructions specified by the user at which a progress info message is printed. More...
 
uint64_t progressMsgThreshold
 
TraceCPU::TraceStats traceStats
 
- Protected Attributes inherited from BaseCPU
Tick instCnt
 Instruction count used for SPARC misc register. More...
 
int _cpuId
 
const uint32_t _socketId
 Each cpu will have a socket ID that corresponds to its physical location in the system. More...
 
RequestorID _instRequestorId
 instruction side request id that must be placed in all requests More...
 
RequestorID _dataRequestorId
 data side request id that must be placed in all requests More...
 
uint32_t _taskId
 An intrenal representation of a task identifier within gem5. More...
 
uint32_t _pid
 The current OS process ID that is executing on this processor. More...
 
bool _switchedOut
 Is the CPU switched out or active? More...
 
const unsigned int _cacheLineSize
 Cache the cache line size that we get from the system. More...
 
std::vector< BaseInterrupts * > interrupts
 
std::vector< ThreadContext * > threadContexts
 
Trace::InstTracertracer
 
Cycles previousCycle
 
CPUState previousState
 
const Cycles pwrGatingLatency
 
const bool powerGatingOnIdle
 
EventFunctionWrapper enterPwrGatingEvent
 
ProbePoints::PMUUPtr ppRetiredInsts
 Instruction commit probe point. More...
 
ProbePoints::PMUUPtr ppRetiredInstsPC
 
ProbePoints::PMUUPtr ppRetiredLoads
 Retired load instructions. More...
 
ProbePoints::PMUUPtr ppRetiredStores
 Retired store instructions. More...
 
ProbePoints::PMUUPtr ppRetiredBranches
 Retired branches (any type) More...
 
ProbePoints::PMUUPtr ppAllCycles
 CPU cycle counter even if any thread Context is suspended. More...
 
ProbePoints::PMUUPtr ppActiveCycles
 CPU cycle counter, only counts if any thread contexts is active. More...
 
ProbePointArg< bool > * ppSleeping
 ProbePoint that signals transitions of threadContexts sets. More...
 

Static Protected Attributes

static int numTraceCPUs = 0
 Number of Trace CPUs in the system used as a shared variable and passed to the CountedExitEvent event used for counting down exit events. More...
 

Additional Inherited Members

- Public Types inherited from BaseCPU
typedef BaseCPUParams Params
 
- Static Public Member Functions inherited from BaseCPU
static int numSimulatedInsts ()
 
static int numSimulatedOps ()
 
static void wakeup (ThreadID tid)
 
static int numSimulatedCPUs ()
 
static Counter numSimulatedInsts ()
 
static Counter numSimulatedOps ()
 
- Public Attributes inherited from BaseCPU
ThreadID numThreads
 Number of threads we're actually simulating (<= SMT_MAX_THREADS). More...
 
Systemsystem
 
Stats::Scalar numCycles
 
Stats::Scalar numWorkItemsStarted
 
Stats::Scalar numWorkItemsCompleted
 
Cycles syscallRetryLatency
 
- Static Public Attributes inherited from BaseCPU
static const uint32_t invldPid = std::numeric_limits<uint32_t>::max()
 Invalid or unknown Pid. More...
 
static const Addr PCMask = ~((Addr)sizeof(TheISA::MachInst) - 1)
 
- Protected Types inherited from BaseCPU
enum  CPUState { CPU_STATE_ON, CPU_STATE_SLEEP, CPU_STATE_WAKEUP }
 

Detailed Description

The trace cpu replays traces generated using the elastic trace probe attached to the O3 CPU model.

The elastic trace is an execution trace with register data dependencies and ordering dependencies annotated to it. The trace cpu also replays a fixed timestamp fetch trace that is also generated by the elastic trace probe. This trace cpu model aims at achieving faster simulation compared to the detailed cpu model and good correlation when the same trace is used for playback on different memory sub-systems.

The TraceCPU inherits from BaseCPU so some virtual methods need to be defined. It has two port subclasses inherited from RequestPort for instruction and data ports. It issues the memory requests deducing the timing from the trace and without performing real execution of micro-ops. As soon as the last dependency for an instruction is complete, its computational delay, also provided in the input trace is added. The dependency-free nodes are maintained in a list, called 'ReadyList', ordered by ready time. Instructions which depend on load stall until the responses for read requests are received thus achieving elastic replay. If the dependency is not found when adding a new node, it is assumed complete. Thus, if this node is found to be completely dependency-free its issue time is calculated and it is added to the ready list immediately. This is encapsulated in the subclass ElasticDataGen.

If ready nodes are issued in an unconstrained way there can be more nodes outstanding which results in divergence in timing compared to the O3CPU. Therefore, the Trace CPU also models hardware resources. A sub-class to model hardware resources contains the maximum sizes of load buffer, store buffer and ROB. If resources are not available, the node is not issued. Such nodes that are pending issue are held in the 'depFreeQueue' structure.

Modeling the ROB size in the Trace CPU as a resource limitation is arguably the most important parameter of all resources. The ROB occupancy is estimated using the newly added field 'robNum'. We need to use ROB number as sequence number is at times much higher due to squashing and trace replay is focused on correct path modeling.

A map called 'inFlightNodes' is added to track nodes that are not only in the readyList but also load nodes that are executed (and thus removed from readyList) but are not complete. ReadyList handles what and when to execute next node while the inFlightNodes is used for resource modelling. The oldest ROB number is updated when any node occupies the ROB or when an entry in the ROB is released. The ROB occupancy is equal to the difference in the ROB number of the newly dependency-free node and the oldest ROB number in flight.

If no node depends on a non load/store node then there is no reason to track it in the dependency graph. We filter out such nodes but count them and add a weight field to the subsequent node that we do include in the trace. The weight field is used to model ROB occupancy during replay.

The depFreeQueue is chosen to be FIFO so that child nodes which are in program order get pushed into it in that order and thus issued in program order, like in the O3CPU. This is also why the dependents is made a sequential container, std::set to std::vector. We only check head of the depFreeQueue as nodes are issued in order and blocking on head models that better than looping the entire queue. An alternative choice would be to inspect top N pending nodes where N is the issue-width. This is left for future as the timing correlation looks good as it is.

At the start of an execution event, first we attempt to issue such pending nodes by checking if appropriate resources have become available. If yes, we compute the execute tick with respect to the time then. Then we proceed to complete nodes from the readyList.

When a read response is received, sometimes a dependency on it that was supposed to be released when it was issued is still not released. This occurs because the dependent gets added to the graph after the read was sent. So the check is made less strict and the dependency is marked complete on read response instead of insisting that it should have been removed on read sent.

There is a check for requests spanning two cache lines as this condition triggers an assert fail in the L1 cache. If it does then truncate the size to access only until the end of that line and ignore the remainder. Strictly-ordered requests are skipped and the dependencies on such requests are handled by simply marking them complete immediately.

A CountedExitEvent that contains a static int belonging to the Trace CPU class as a down counter is used to implement multi Trace CPU simulation exit.

Definition at line 140 of file trace_cpu.hh.

Constructor & Destructor Documentation

◆ TraceCPU()

TraceCPU::TraceCPU ( TraceCPUParams *  params)

Definition at line 45 of file trace_cpu.cc.

References schedIcacheNext().

◆ ~TraceCPU()

TraceCPU::~TraceCPU ( )

Definition at line 80 of file trace_cpu.cc.

Member Function Documentation

◆ checkAndSchedExitEvent()

void TraceCPU::checkAndSchedExitEvent ( )
protected

This is called when either generator finishes executing from the trace.

Definition at line 193 of file trace_cpu.cc.

References curTick(), enableEarlyExit, execCompleteEvent, exitSimLoop(), inform, name(), and oneTraceComplete.

Referenced by schedDcacheNext(), and schedIcacheNext().

◆ dcacheRecvTimingResp()

void TraceCPU::dcacheRecvTimingResp ( PacketPtr  pkt)

When data cache port receives a response, this calls the dcache generator method handle to complete the load writeback.

Parameters
pktPointer to packet received

Definition at line 1155 of file trace_cpu.cc.

References TraceCPU::ElasticDataGen::completeMemAccess(), dcacheGen, and DPRINTF.

Referenced by TraceCPU::DcachePort::recvTimingResp().

◆ dcacheRetryRecvd()

void TraceCPU::dcacheRetryRecvd ( )

When data cache port receives a retry, schedule event dcacheNextEvent.

Definition at line 1113 of file trace_cpu.cc.

References curTick(), dcacheNextEvent, and DPRINTF.

Referenced by TraceCPU::DcachePort::recvReqRetry().

◆ getDataPort()

Port& TraceCPU::getDataPort ( )
inlinevirtual

Used to get a reference to the dcache port.

Implements BaseCPU.

Definition at line 1161 of file trace_cpu.hh.

References dcachePort.

Referenced by takeOverFrom().

◆ getInstPort()

Port& TraceCPU::getInstPort ( )
inlinevirtual

Used to get a reference to the icache port.

Implements BaseCPU.

Definition at line 1158 of file trace_cpu.hh.

References icachePort.

Referenced by takeOverFrom().

◆ icacheRetryRecvd()

void TraceCPU::icacheRetryRecvd ( )

When instruction cache port receives a retry, schedule event icacheNextEvent.

Definition at line 1103 of file trace_cpu.cc.

References curTick(), DPRINTF, and icacheNextEvent.

Referenced by TraceCPU::IcachePort::recvReqRetry().

◆ init()

void TraceCPU::init ( )

◆ schedDcacheNext()

void TraceCPU::schedDcacheNext ( )
protected

This is the control flow that uses the functionality of the dcacheGen to replay the trace.

It calls execute(). It checks if execution is complete and schedules an event to exit simulation accordingly.

Definition at line 179 of file trace_cpu.cc.

References checkAndSchedExitEvent(), dcacheGen, DPRINTF, TraceCPU::ElasticDataGen::execute(), TraceCPU::ElasticDataGen::isExecComplete(), and BaseCPU::numCycles.

◆ schedDcacheNextEvent()

void TraceCPU::schedDcacheNextEvent ( Tick  when)

Schedule event dcacheNextEvent at the given tick.

Parameters
whenTick at which to schedule event

Definition at line 1123 of file trace_cpu.cc.

References dcacheNextEvent, DPRINTF, TraceCPU::TraceStats::numSchedDcacheEvent, Event::scheduled(), traceStats, and Event::when().

Referenced by TraceCPU::ElasticDataGen::completeMemAccess(), and TraceCPU::ElasticDataGen::execute().

◆ schedIcacheNext()

void TraceCPU::schedIcacheNext ( )
protected

This is the control flow that uses the functionality of the icacheGen to replay the trace.

It calls tryNext(). If it returns true then next event is scheduled at curTick() plus delta. If it returns false then delta is ignored and control is brought back via recvRetry().

Definition at line 154 of file trace_cpu.cc.

References checkAndSchedExitEvent(), curTick(), DPRINTF, icacheGen, icacheNextEvent, TraceCPU::FixedRetryGen::isTraceComplete(), TraceCPU::TraceStats::numSchedIcacheEvent, TraceCPU::FixedRetryGen::tickDelta(), traceStats, and TraceCPU::FixedRetryGen::tryNext().

Referenced by TraceCPU().

◆ takeOverFrom()

void TraceCPU::takeOverFrom ( BaseCPU cpu)
virtual

Load the state of a CPU from the previous CPU object, invoked on all new CPUs that are about to be switched in.

A CPU model implementing this method is expected to initialize its state from the old CPU and connect its memory (unless they are already connected) to the memories connected to the old CPU.

Parameters
cpuCPU to initialize read state from.

Reimplemented from BaseCPU.

Definition at line 103 of file trace_cpu.cc.

References BaseCPU::getDataPort(), getDataPort(), BaseCPU::getInstPort(), getInstPort(), and Port::takeOverFrom().

◆ totalInsts()

Counter TraceCPU::totalInsts ( ) const
inlinevirtual

This is a pure virtual function in BaseCPU.

As we don't know how many insts are in the trace but only know how how many micro-ops are we cannot count this stat.

Returns
0

Implements BaseCPU.

Definition at line 156 of file trace_cpu.hh.

◆ totalOps()

Counter TraceCPU::totalOps ( ) const
inlinevirtual

Return totalOps as the number of committed micro-ops plus the speculatively issued loads that are modelled in the TraceCPU replay.

Returns
number of micro-ops i.e. nodes in the elastic data generator

Implements BaseCPU.

Definition at line 167 of file trace_cpu.hh.

References TraceCPU::TraceStats::numOps, traceStats, and Stats::ScalarBase< Derived, Stor >::value().

◆ updateNumOps()

void TraceCPU::updateNumOps ( uint64_t  rob_num)

◆ wakeup()

void TraceCPU::wakeup ( ThreadID  tid = 0)
inlinevirtual

Implements BaseCPU.

Definition at line 179 of file trace_cpu.hh.

Member Data Documentation

◆ dataRequestorID

const RequestorID TraceCPU::dataRequestorID
protected

Requestor id for data read and write requests.

Definition at line 328 of file trace_cpu.hh.

◆ dataTraceFile

std::string TraceCPU::dataTraceFile
protected

Definition at line 331 of file trace_cpu.hh.

Referenced by init().

◆ dcacheGen

ElasticDataGen TraceCPU::dcacheGen
protected

Instance of ElasticDataGen to replay data read and write requests.

Definition at line 1072 of file trace_cpu.hh.

Referenced by dcacheRecvTimingResp(), init(), and schedDcacheNext().

◆ dcacheNextEvent

EventFunctionWrapper TraceCPU::dcacheNextEvent
protected

Event for the control flow method schedDcacheNext()

Definition at line 1093 of file trace_cpu.hh.

Referenced by dcacheRetryRecvd(), init(), and schedDcacheNextEvent().

◆ dcachePort

DcachePort TraceCPU::dcachePort
protected

Port to connect to L1 data cache.

Definition at line 322 of file trace_cpu.hh.

Referenced by getDataPort().

◆ enableEarlyExit

const bool TraceCPU::enableEarlyExit
protected

Exit when any one Trace CPU completes its execution.

If this is configured true then the execCompleteEvent is not scheduled.

Definition at line 1128 of file trace_cpu.hh.

Referenced by checkAndSchedExitEvent(), and init().

◆ execCompleteEvent

CountedExitEvent* TraceCPU::execCompleteEvent
protected

A CountedExitEvent which when serviced decrements the counter.

A sim exit event is scheduled when the counter equals zero, that is all instances of Trace CPU have had their execCompleteEvent serviced.

Definition at line 1122 of file trace_cpu.hh.

Referenced by checkAndSchedExitEvent(), and init().

◆ icacheGen

FixedRetryGen TraceCPU::icacheGen
protected

Instance of FixedRetryGen to replay instruction read requests.

Definition at line 1069 of file trace_cpu.hh.

Referenced by init(), and schedIcacheNext().

◆ icacheNextEvent

EventFunctionWrapper TraceCPU::icacheNextEvent
protected

Event for the control flow method schedIcacheNext()

Definition at line 1090 of file trace_cpu.hh.

Referenced by icacheRetryRecvd(), init(), and schedIcacheNext().

◆ icachePort

IcachePort TraceCPU::icachePort
protected

Port to connect to L1 instruction cache.

Definition at line 319 of file trace_cpu.hh.

Referenced by getInstPort().

◆ instRequestorID

const RequestorID TraceCPU::instRequestorID
protected

Requestor id for instruction read requests.

Definition at line 325 of file trace_cpu.hh.

◆ instTraceFile

std::string TraceCPU::instTraceFile
protected

File names for input instruction and data traces.

Definition at line 331 of file trace_cpu.hh.

Referenced by init().

◆ numTraceCPUs

int TraceCPU::numTraceCPUs = 0
staticprotected

Number of Trace CPUs in the system used as a shared variable and passed to the CountedExitEvent event used for counting down exit events.

It is incremented in the constructor call so that the total is arrived at automatically.

Definition at line 1115 of file trace_cpu.hh.

Referenced by init().

◆ oneTraceComplete

bool TraceCPU::oneTraceComplete
protected

Set to true when one of the generators finishes replaying its trace.

Definition at line 1099 of file trace_cpu.hh.

Referenced by checkAndSchedExitEvent().

◆ progressMsgInterval

const uint64_t TraceCPU::progressMsgInterval
protected

Interval of committed instructions specified by the user at which a progress info message is printed.

Definition at line 1134 of file trace_cpu.hh.

Referenced by updateNumOps().

◆ progressMsgThreshold

uint64_t TraceCPU::progressMsgThreshold
protected

Definition at line 1141 of file trace_cpu.hh.

Referenced by updateNumOps().

◆ traceOffset

Tick TraceCPU::traceOffset
protected

This stores the time offset in the trace, which is taken away from the ready times of requests.

This is specially useful because the time offset can be very large if the traces are generated from the middle of a program.

Definition at line 1107 of file trace_cpu.hh.

Referenced by init().

◆ traceStats

TraceCPU::TraceStats TraceCPU::traceStats
protected

The documentation for this class was generated from the following files:

Generated on Wed Sep 30 2020 14:02:33 for gem5 by doxygen 1.8.17