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/**
* Copyright (c) 2018 Inria
* 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: Daniel Carvalho
*/
#include "mem/cache/replacement_policies/brrip_rp.hh"
#include "base/random.hh"
#include "debug/CacheRepl.hh"
BRRIPRP::BRRIPRP(const Params *p)
: BaseReplacementPolicy(p),
maxRRPV(p->max_RRPV), hitPriority(p->hit_priority), btp(p->btp)
{
if (maxRRPV == 0){
fatal("max_RRPV should be greater than zero.\n");
}
}
void
BRRIPRP::touch(CacheBlk *blk)
{
BaseReplacementPolicy::touch(blk);
// Update RRPV if not 0 yet
// Every hit in HP mode makes the block the last to be evicted, while
// in FP mode a hit makes the block less likely to be evicted
if (hitPriority) {
blk->rrpv = 0;
} else if (blk->rrpv > 0) {
blk->rrpv--;
}
}
void
BRRIPRP::reset(CacheBlk *blk)
{
BaseReplacementPolicy::reset(blk);
// Reset RRPV
// Blocks are inserted as "long re-reference" if lower than btp,
// "distant re-reference" otherwise
if (random_mt.random<unsigned>(1, 100) <= btp) {
blk->rrpv = maxRRPV-1;
} else {
blk->rrpv = maxRRPV;
}
}
CacheBlk*
BRRIPRP::getVictim(const ReplacementCandidates& candidates)
{
// There must be at least one replacement candidate
assert(candidates.size() > 0);
// Use visitor to search for the victim
CacheBlk* blk = candidates[0];
for (const auto& candidate : candidates) {
// Stop iteration if found an invalid block
if (!candidate->isValid()) {
blk = candidate;
blk->rrpv = maxRRPV;
break;
// Update victim block if necessary
} else if (candidate->rrpv > blk->rrpv) {
blk = candidate;
}
}
// Make sure we don't have an invalid rrpv
assert(blk->rrpv <= maxRRPV);
// Get difference of block's RRPV to the highest possible RRPV in
// order to update the RRPV of all the other blocks accordingly
unsigned diff = maxRRPV - blk->rrpv;
// No need to update RRPV if there is no difference
if (diff > 0){
// Update RRPV of all candidates
for (const auto& candidate : candidates) {
// Update the block's RPPV with the new value
candidate->rrpv += diff;
}
}
DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
blk->set, blk->way);
return blk;
}
BRRIPRP*
BRRIPRPParams::create()
{
return new BRRIPRP(this);
}
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