dvfs_handler.cc

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 * Copyright (c) 2013-2014 ARM Limited
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#include "sim/dvfs_handler.hh"
 
#include <set>
#include <utility>
 
#include "base/trace.hh"
#include "debug/DVFS.hh"
#include "params/DVFSHandler.hh"
#include "sim/serialize.hh"
#include "sim/stat_control.hh"
#include "sim/voltage_domain.hh"
 
namespace gem5
{
 
//
//
// DVFSHandler methods implementation
//
 
DVFSHandler::DVFSHandler(const Params &p)
    : SimObject(p),
      sysClkDomain(p.sys_clk_domain),
      enableHandler(p.enable),
      _transLatency(p.transition_latency)
{
    // Check supplied list of domains for sanity and add them to the
    // domain ID -> domain* hash
    for (auto dit = p.domains.begin(); dit != p.domains.end(); ++dit) {
        SrcClockDomain *d = *dit;
        DomainID domain_id = d->domainID();
 
        fatal_if(sysClkDomain == d, "DVFS: Domain config list has a "\
                 "system clk domain entry");
        fatal_if(domain_id == SrcClockDomain::emptyDomainID,
                 "DVFS: Controlled domain %s needs to have a properly "\
                 " assigned ID.\n", d->name());
 
        auto entry = std::make_pair(domain_id, d);
        bool new_elem = domains.insert(entry).second;
        fatal_if(!new_elem, "DVFS: Domain %s with ID %d does not have a "\
                 "unique ID.\n", d->name(), domain_id);
 
        // Create a dedicated event slot per known domain ID
        UpdateEvent *event = &updatePerfLevelEvents[domain_id];
        event->domainIDToSet = d->domainID();
 
        // Add domain ID to the list of domains
        domainIDList.push_back(d->domainID());
    }
    UpdateEvent::dvfsHandler = this;
}
 
DVFSHandler *DVFSHandler::UpdateEvent::dvfsHandler;
 
DVFSHandler::DomainID
DVFSHandler::domainID(uint32_t index) const
{
    fatal_if(index >= numDomains(), "DVFS: Requested index out of "\
             "bound, max value %d\n", (domainIDList.size() - 1));
 
    assert(domains.find(domainIDList[index]) != domains.end());
 
    return domainIDList[index];
}
 
bool
DVFSHandler::validDomainID(DomainID domain_id) const
{
    assert(isEnabled());
    // This is ensure that the domain id as requested by the software is
    // availabe in the handler.
    if (domains.find(domain_id) != domains.end())
        return true;
    warn("DVFS: invalid domain ID %d, the DVFS handler does not handle this "\
         "domain\n", domain_id);
    return false;
}
 
bool
DVFSHandler::perfLevel(DomainID domain_id, PerfLevel perf_level)
{
    assert(isEnabled());
 
    DPRINTF(DVFS, "DVFS: setPerfLevel domain %d -> %d\n", domain_id, perf_level);
 
    auto d = findDomain(domain_id);
    if (!d->validPerfLevel(perf_level)) {
        warn("DVFS: invalid performance level %d for domain ID %d, request "\
             "ignored\n", perf_level, domain_id);
        return false;
    }
 
    UpdateEvent *update_event = &updatePerfLevelEvents[domain_id];
    // Drop an old DVFS change request once we have established that this is a
    // reasonable request
    if (update_event->scheduled()) {
        DPRINTF(DVFS, "DVFS: Overwriting the previous DVFS event.\n");
        deschedule(update_event);
    }
 
    update_event->perfLevelToSet = perf_level;
 
    // State changes that restore to the current state (and / or overwrite a not
    // yet completed in-flight request) will be squashed
    if (d->perfLevel() == perf_level) {
        DPRINTF(DVFS, "DVFS: Ignoring ineffective performance level change "\
                "%d -> %d\n", d->perfLevel(), perf_level);
        return false;
    }
 
    // At this point, a new transition will certainly take place -> schedule
    Tick when = curTick() + _transLatency;
    DPRINTF(DVFS, "DVFS: Update for perf event scheduled for %ld\n", when);
 
    schedule(update_event, when);
    return true;
}
 
void
DVFSHandler::UpdateEvent::updatePerfLevel()
{
    // Perform explicit stats dump for power estimation before performance
    // level migration
    statistics::dump();
    statistics::reset();
 
    // Update the performance level in the clock domain
    auto d = dvfsHandler->findDomain(domainIDToSet);
    assert(d->perfLevel() != perfLevelToSet);
 
    d->perfLevel(perfLevelToSet);
}
 
double
DVFSHandler::voltageAtPerfLevel(DomainID domain_id, PerfLevel perf_level) const
{
    VoltageDomain *d = findDomain(domain_id)->voltageDomain();
    assert(d);
    PerfLevel n = d->numVoltages();
    if (perf_level < n)
        return d->voltage(perf_level);
 
    // Request outside of the range of the voltage domain
    if (n == 1) {
        DPRINTF(DVFS, "DVFS: Request for perf-level %i for single-point "\
                "voltage domain %s.  Returning voltage at level 0: %.2f "\
                "V\n", perf_level, d->name(), d->voltage(0));
        // Special case for single point voltage domain -> same voltage for
        // all points
        return d->voltage(0);
    }
 
    warn("DVFSHandler %s reads illegal voltage level %u from "\
         "VoltageDomain %s. Returning 0 V\n", name(), perf_level, d->name());
    return 0.;
}
 
void
DVFSHandler::serialize(CheckpointOut &cp) const
{
    //This is to ensure that the handler status is maintained during the
    //entire simulation run and not changed from command line during checkpoint
    //and restore
    SERIALIZE_SCALAR(enableHandler);
 
    // Pull out the hashed data structure into easy-to-serialise arrays;
    // ensuring that the data associated with any pending update event is saved
    std::vector<DomainID> domain_ids;
    std::vector<PerfLevel> perf_levels;
    std::vector<Tick> whens;
    for (const auto &ev_pair : updatePerfLevelEvents) {
        DomainID id = ev_pair.first;
        const UpdateEvent *event = &ev_pair.second;
 
        assert(id == event->domainIDToSet);
        domain_ids.push_back(id);
        perf_levels.push_back(event->perfLevelToSet);
        whens.push_back(event->scheduled() ? event->when() : 0);
    }
    SERIALIZE_CONTAINER(domain_ids);
    SERIALIZE_CONTAINER(perf_levels);
    SERIALIZE_CONTAINER(whens);
}
 
void
DVFSHandler::unserialize(CheckpointIn &cp)
{
    bool temp = enableHandler;
 
    UNSERIALIZE_SCALAR(enableHandler);
 
    if (temp != enableHandler) {
        warn("DVFS: Forcing enable handler status to unserialized value of %d",
             enableHandler);
    }
 
    // Reconstruct the map of domain IDs and their scheduled events
    std::vector<DomainID> domain_ids;
    std::vector<PerfLevel> perf_levels;
    std::vector<Tick> whens;
    UNSERIALIZE_CONTAINER(domain_ids);
    UNSERIALIZE_CONTAINER(perf_levels);
    UNSERIALIZE_CONTAINER(whens);
 
    for (size_t i = 0; i < domain_ids.size(); ++i) {;
        UpdateEvent *event = &updatePerfLevelEvents[domain_ids[i]];
 
        event->domainIDToSet = domain_ids[i];
        event->perfLevelToSet = perf_levels[i];
 
        // Schedule all previously scheduled events
        if (whens[i])
            schedule(event, whens[i]);
    }
    UpdateEvent::dvfsHandler = this;
}
 
} // namespace gem5