brrip_rp.cc revision 12626:e161d7725d4b 
1/**
2 * Copyright (c) 2018 Inria
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met: redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer;
9 * redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution;
12 * neither the name of the copyright holders nor the names of its
13 * contributors may be used to endorse or promote products derived from
14 * this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Authors: Daniel Carvalho
29 */
30
31#include "mem/cache/replacement_policies/brrip_rp.hh"
32
33#include "base/random.hh"
34#include "debug/CacheRepl.hh"
35
36BRRIPRP::BRRIPRP(const Params *p)
37    : BaseReplacementPolicy(p),
38      maxRRPV(p->max_RRPV), hitPriority(p->hit_priority), btp(p->btp)
39{
40    if (maxRRPV == 0){
41        fatal("max_RRPV should be greater than zero.\n");
42    }
43}
44
45void
46BRRIPRP::touch(CacheBlk *blk)
47{
48    BaseReplacementPolicy::touch(blk);
49
50    // Update RRPV if not 0 yet
51    // Every hit in HP mode makes the block the last to be evicted, while
52    // in FP mode a hit makes the block less likely to be evicted
53    if (hitPriority) {
54        blk->rrpv = 0;
55    } else if (blk->rrpv > 0) {
56        blk->rrpv--;
57    }
58}
59
60void
61BRRIPRP::reset(CacheBlk *blk)
62{
63    BaseReplacementPolicy::reset(blk);
64
65    // Reset RRPV
66    // Blocks are inserted as "long re-reference" if lower than btp,
67    // "distant re-reference" otherwise
68    if (random_mt.random<unsigned>(1, 100) <= btp) {
69        blk->rrpv = maxRRPV-1;
70    } else {
71        blk->rrpv = maxRRPV;
72    }
73}
74
75CacheBlk*
76BRRIPRP::getVictim(const ReplacementCandidates& candidates)
77{
78    // There must be at least one replacement candidate
79    assert(candidates.size() > 0);
80
81    // Use visitor to search for the victim
82    CacheBlk* blk = candidates[0];
83    for (const auto& candidate : candidates) {
84        // Stop iteration if found an invalid block
85        if (!candidate->isValid()) {
86            blk = candidate;
87            blk->rrpv = maxRRPV;
88            break;
89        // Update victim block if necessary
90        } else if (candidate->rrpv > blk->rrpv) {
91            blk = candidate;
92        }
93    }
94
95    // Make sure we don't have an invalid rrpv
96    assert(blk->rrpv <= maxRRPV);
97
98    // Get difference of block's RRPV to the highest possible RRPV in
99    // order to update the RRPV of all the other blocks accordingly
100    unsigned diff = maxRRPV - blk->rrpv;
101
102    // No need to update RRPV if there is no difference
103    if (diff > 0){
104        // Update RRPV of all candidates
105        for (const auto& candidate : candidates) {
106            // Update the block's RPPV with the new value
107            candidate->rrpv += diff;
108        }
109    }
110
111    DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
112            blk->set, blk->way);
113
114    return blk;
115}
116
117BRRIPRP*
118BRRIPRPParams::create()
119{
120    return new BRRIPRP(this);
121}
122