random_rp.cc revision 12600:e670dd17c8cf 
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/random_rp.hh"
32
33#include "base/random.hh"
34#include "debug/CacheRepl.hh"
35
36RandomRP::RandomRP(const Params *p)
37    : BaseReplacementPolicy(p)
38{
39}
40
41CacheBlk*
42RandomRP::getVictim(const ReplacementCandidates& candidates)
43{
44    // There must be at least one replacement candidate
45    assert(candidates.size() > 0);
46
47    // Choose one candidate at random
48    CacheBlk* blk = candidates[random_mt.random<unsigned>(0,
49                                    candidates.size() - 1)];
50
51    // Visit all candidates to find an invalid entry
52    for (const auto& candidate : candidates) {
53        // Give priority to victimise invalid entries
54        if (!candidate->isValid()){
55            blk = candidate;
56            break;
57        }
58    }
59
60    // If no invalid blocks were found, choose one of the candidates randomly
61    DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
62            blk->set, blk->way);
63
64    return blk;
65}
66
67RandomRP*
68RandomRPParams::create()
69{
70    return new RandomRP(this);
71}
72