Linux Kernel Module Cheat

24.10.3.4. gem5 stats internals

This describes the internals of the gem5 m5out/stats.txt file.

GDB call stack to dumpstats:

Stats::pythonDump () at build/ARM/python/pybind11/stats.cc:58
Stats::StatEvent::process() ()
GlobalEvent::BarrierEvent::process (this=0x555559fa6a80) at build/ARM/sim/global_event.cc:131
EventQueue::serviceOne (this=this@entry=0x555558c36080) at build/ARM/sim/eventq.cc:228
doSimLoop (eventq=0x555558c36080) at build/ARM/sim/simulate.cc:219
simulate (num_cycles=<optimized out>) at build/ARM/sim/simulate.cc:132

Stats::pythonDump does:

void
pythonDump()
{
    py::module m = py::module::import("m5.stats");
    m.attr("dump")();
}

This calls src/python/m5/stats/init.py in def dump does the main dumping

That function does notably:

    for output in outputList:
        if output.valid():
            output.begin()
            for stat in stats_list:
                stat.visit(output)
            output.end()

begin and end are defined in C++ and output the header and tail respectively

void
Text::begin()
{
    ccprintf(*stream, "\n---------- Begin Simulation Statistics ----------\n");
}

void
Text::end()
{
    ccprintf(*stream, "\n---------- End Simulation Statistics   ----------\n");
    stream->flush();
}

stats_list contains the stats, and stat.visit prints them, outputList contains by default just the text output. I don’t see any other types of output in gem5, but likely JSON / binary formats could be envisioned.

Tested in gem5 b4879ae5b0b6644e6836b0881e4da05c64a6550d.