q_policy.cc

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 * Author: Matteo Andreozzi
 */

#include "mem/qos/q_policy.hh"

#include <unordered_map>
#include <utility>

#include "debug/QOS.hh"
#include "enums/QoSQPolicy.hh"
#include "mem/qos/mem_ctrl.hh"

namespace QoS {

QueuePolicy*
QueuePolicy::create(const QoSMemCtrlParams* p)
{
    switch (p->qos_q_policy) {
      case Enums::QoSQPolicy::fifo:
        return new FifoQueuePolicy(p);
      case Enums::QoSQPolicy::lrg:
        return new LrgQueuePolicy(p);
      case Enums::QoSQPolicy::lifo:
      default:
        return new LifoQueuePolicy(p);
    }
}

QueuePolicy::PacketQueue::iterator
LrgQueuePolicy::selectPacket(PacketQueue* q)
{
    QueuePolicy::PacketQueue::iterator ret = q->end();

    // Tracks one packet per master in the queue
    std::unordered_map<MasterID, QueuePolicy::PacketQueue::iterator> track;

    // Cycle queue only once
    for (auto pkt_it = q->begin(); pkt_it != q->end(); ++pkt_it) {

        const auto& pkt = *pkt_it;

        panic_if(!pkt->req,
                 "QoSQPolicy::lrg detected packet without request");

        // Get Request MasterID
        MasterID m_id = pkt->req->masterId();
        DPRINTF(QOS, "QoSQPolicy::lrg checking packet "
                     "from queue with id %d\n", m_id);

        // Check if this is a known master.
        panic_if(memCtrl->hasMaster(m_id),
                 "%s: Unrecognized Master\n", __func__);

        panic_if(toServe.size() > 0,
                 "%s: toServe list is empty\n", __func__);

        if (toServe.front() == m_id) {
            DPRINTF(QOS, "QoSQPolicy::lrg matched to served "
                         "master id %d\n", m_id);
            // This packet matches the MasterID to be served next
            // move toServe front to back
            toServe.push_back(m_id);
            toServe.pop_front();

            return pkt_it;
        }

        // The master generating the packet is not first in the toServe list
        // (Doesn't have the highest priority among masters)
        // Check if this is the first packet seen with its master ID
        // and remember it. Then keep looping over the remaining packets
        // in the queue.
        if (track.find(m_id) == track.end()) {
            track[m_id] = pkt_it;
            DPRINTF(QOS, "QoSQPolicy::lrg tracking a packet for "
                         "master id %d\n", m_id);
        }
    }

    // If here, the current master to be serviced doesn't have a pending
    // packet in the queue: look for the next master in the list.
    for (const auto& masterId : toServe) {
        DPRINTF(QOS, "QoSQPolicy::lrg evaluating alternative "
                     "master id %d\n", masterId);

        if (track.find(masterId) != track.end()) {
            ret = track[masterId];
            DPRINTF(QOS, "QoSQPolicy::lrg master id "
                         "%d selected for service\n", masterId);

            return ret;
        }
    }

    DPRINTF(QOS, "QoSQPolicy::lrg no packet was serviced\n");

    // Ret will be : packet to serve if any found or queue begin
    // (end if queue is empty)
    return ret;
}

void
LrgQueuePolicy::enqueuePacket(PacketPtr pkt)
{
    MasterID m_id = pkt->masterId();
    if (!memCtrl->hasMaster(m_id)) {
        toServe.push_back(m_id);
    }
};

} // namespace QoS