src/mem/probes/stack_dist.cc

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#include "mem/probes/stack_dist.hh"

#include "params/StackDistProbe.hh"
#include "sim/system.hh"

namespace gem5
{

StackDistProbe::StackDistProbe(const StackDistProbeParams &p)
    : BaseMemProbe(p),
      lineSize(p.line_size),
      disableLinearHists(p.disable_linear_hists),
      disableLogHists(p.disable_log_hists),
      calc(p.verify),
      stats(this)
{
    fatal_if(p.system->cacheLineSize() > p.line_size,
             "The stack distance probe must use a cache line size that is "
             "larger or equal to the system's cahce line size.");
}

StackDistProbe::StackDistProbeStats::StackDistProbeStats(
    StackDistProbe *parent)
    : statistics::Group(parent),
      ADD_STAT(readLinearHist, statistics::units::Count::get(),
               "Reads linear distribution"),
      ADD_STAT(readLogHist, statistics::units::Ratio::get(),
               "Reads logarithmic distribution"),
      ADD_STAT(writeLinearHist, statistics::units::Count::get(),
               "Writes linear distribution"),
      ADD_STAT(writeLogHist, statistics::units::Ratio::get(),
               "Writes logarithmic distribution"),
      ADD_STAT(infiniteSD, statistics::units::Count::get(),
               "Number of requests with infinite stack distance")
{
    using namespace statistics;

    const StackDistProbeParams &p =
        dynamic_cast<const StackDistProbeParams &>(parent->params());

    readLinearHist
        .init(p.linear_hist_bins)
        .flags(parent->disableLinearHists ? nozero : pdf);

    readLogHist
        .init(p.log_hist_bins)
        .flags(parent->disableLogHists ? nozero : pdf);

    writeLinearHist
        .init(p.linear_hist_bins)
        .flags(parent->disableLinearHists ? nozero : pdf);

    writeLogHist
        .init(p.log_hist_bins)
        .flags(parent->disableLogHists ? nozero : pdf);

    infiniteSD
        .flags(nozero);
}

void
StackDistProbe::handleRequest(const probing::PacketInfo &pkt_info)
{
    // only capturing read and write requests (which allocate in the
    // cache)
    if (!pkt_info.cmd.isRead() && !pkt_info.cmd.isWrite())
        return;

    // Align the address to a cache line size
    const Addr aligned_addr(roundDown(pkt_info.addr, lineSize));

    // Calculate the stack distance
    const uint64_t sd(calc.calcStackDistAndUpdate(aligned_addr).first);
    if (sd == StackDistCalc::Infinity) {
        stats.infiniteSD++;
        return;
    }

    // Sample the stack distance of the address in linear bins
    if (!disableLinearHists) {
        if (pkt_info.cmd.isRead())
            stats.readLinearHist.sample(sd);
        else
            stats.writeLinearHist.sample(sd);
    }

    if (!disableLogHists) {
        int sd_lg2 = sd == 0 ? 1 : floorLog2(sd);

        // Sample the stack distance of the address in log bins
        if (pkt_info.cmd.isRead())
            stats.readLogHist.sample(sd_lg2);
        else
            stats.writeLogHist.sample(sd_lg2);
    }
}

} // namespace gem5