src/mem/cache/prefetch/ghb.cc

/*
 * Copyright (c) 2005 The Regents of The University of Michigan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Authors: Ron Dreslinski
 *          Steve Reinhardt
 */

/**
 * @file
 * GHB Prefetcher implementation.
 */

#include "mem/cache/prefetch/ghb.hh"
#include "arch/isa_traits.hh"

void
GHBPrefetcher::calculatePrefetch(PacketPtr &pkt, std::list<Addr> &addresses,
                                 std::list<Tick> &delays)
{
    Addr blkAddr = pkt->getAddr() & ~(Addr)(this->blkSize-1);
    int cpuID = pkt->req->getCpuNum();
    if (!useCPUId) cpuID = 0;


    int new_stride = blkAddr - last_miss_addr[cpuID];
    int old_stride = last_miss_addr[cpuID] -
        second_last_miss_addr[cpuID];

    second_last_miss_addr[cpuID] = last_miss_addr[cpuID];
    last_miss_addr[cpuID] = blkAddr;

    if (new_stride == old_stride) {
        for (int d=1; d <= degree; d++) {
            Addr newAddr = blkAddr + d * new_stride;
            if (this->pageStop &&
                (blkAddr & ~(TheISA::VMPageSize - 1)) !=
                (newAddr & ~(TheISA::VMPageSize - 1)))
            {
                //Spanned the page, so now stop
                this->pfSpanPage += degree - d + 1;
                return;
            }
            else
            {
                addresses.push_back(newAddr);
                delays.push_back(latency);
            }
        }
    }
}