fa_lru.cc revision 9288:3d6da8559605 
1/*
2 * Copyright (c) 2003-2005 The Regents of The University of Michigan
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: Erik Hallnor
29 */
30
31/**
32 * @file
33 * Definitions a fully associative LRU tagstore.
34 */
35
36#include <cassert>
37#include <sstream>
38
39#include "base/intmath.hh"
40#include "base/misc.hh"
41#include "mem/cache/tags/fa_lru.hh"
42
43using namespace std;
44
45FALRU::FALRU(unsigned _blkSize, unsigned _size, Cycles hit_latency)
46    : blkSize(_blkSize), size(_size), hitLatency(hit_latency)
47{
48    if (!isPowerOf2(blkSize))
49        fatal("cache block size (in bytes) `%d' must be a power of two",
50              blkSize);
51    if (!(hitLatency > 0))
52        fatal("Access latency in cycles must be at least one cycle");
53    if (!isPowerOf2(size))
54        fatal("Cache Size must be power of 2 for now");
55
56    // Track all cache sizes from 128K up by powers of 2
57    numCaches = floorLog2(size) - 17;
58    if (numCaches >0){
59        cacheBoundaries = new FALRUBlk *[numCaches];
60        cacheMask = (1 << numCaches) - 1;
61    } else {
62        cacheMask = 0;
63    }
64
65    warmedUp = false;
66    warmupBound = size/blkSize;
67    numBlocks = size/blkSize;
68
69    blks = new FALRUBlk[numBlocks];
70    head = &(blks[0]);
71    tail = &(blks[numBlocks-1]);
72
73    head->prev = NULL;
74    head->next = &(blks[1]);
75    head->inCache = cacheMask;
76
77    tail->prev = &(blks[numBlocks-2]);
78    tail->next = NULL;
79    tail->inCache = 0;
80
81    unsigned index = (1 << 17) / blkSize;
82    unsigned j = 0;
83    int flags = cacheMask;
84    for (unsigned i = 1; i < numBlocks - 1; i++) {
85        blks[i].inCache = flags;
86        if (i == index - 1){
87            cacheBoundaries[j] = &(blks[i]);
88            flags &= ~ (1<<j);
89            ++j;
90            index = index << 1;
91        }
92        blks[i].prev = &(blks[i-1]);
93        blks[i].next = &(blks[i+1]);
94        blks[i].isTouched = false;
95    }
96    assert(j == numCaches);
97    assert(index == numBlocks);
98    //assert(check());
99}
100
101FALRU::~FALRU()
102{
103    if (numCaches)
104        delete[] cacheBoundaries;
105
106    delete[] blks;
107}
108
109void
110FALRU::regStats(const string &name)
111{
112    using namespace Stats;
113    BaseTags::regStats(name);
114    hits
115        .init(numCaches+1)
116        .name(name + ".falru_hits")
117        .desc("The number of hits in each cache size.")
118        ;
119    misses
120        .init(numCaches+1)
121        .name(name + ".falru_misses")
122        .desc("The number of misses in each cache size.")
123        ;
124    accesses
125        .name(name + ".falru_accesses")
126        .desc("The number of accesses to the FA LRU cache.")
127        ;
128
129    for (unsigned i = 0; i <= numCaches; ++i) {
130        stringstream size_str;
131        if (i < 3){
132            size_str << (1<<(i+7)) <<"K";
133        } else {
134            size_str << (1<<(i-3)) <<"M";
135        }
136
137        hits.subname(i, size_str.str());
138        hits.subdesc(i, "Hits in a " + size_str.str() +" cache");
139        misses.subname(i, size_str.str());
140        misses.subdesc(i, "Misses in a " + size_str.str() +" cache");
141    }
142}
143
144FALRUBlk *
145FALRU::hashLookup(Addr addr) const
146{
147    tagIterator iter = tagHash.find(addr);
148    if (iter != tagHash.end()) {
149        return (*iter).second;
150    }
151    return NULL;
152}
153
154void
155FALRU::invalidate(FALRU::BlkType *blk)
156{
157    assert(blk);
158    tagsInUse--;
159}
160
161FALRUBlk*
162FALRU::accessBlock(Addr addr, Cycles &lat, int context_src, int *inCache)
163{
164    accesses++;
165    int tmp_in_cache = 0;
166    Addr blkAddr = blkAlign(addr);
167    FALRUBlk* blk = hashLookup(blkAddr);
168
169    if (blk && blk->isValid()) {
170        assert(blk->tag == blkAddr);
171        tmp_in_cache = blk->inCache;
172        for (unsigned i = 0; i < numCaches; i++) {
173            if (1<<i & blk->inCache) {
174                hits[i]++;
175            } else {
176                misses[i]++;
177            }
178        }
179        hits[numCaches]++;
180        if (blk != head){
181            moveToHead(blk);
182        }
183    } else {
184        blk = NULL;
185        for (unsigned i = 0; i <= numCaches; ++i) {
186            misses[i]++;
187        }
188    }
189    if (inCache) {
190        *inCache = tmp_in_cache;
191    }
192
193    lat = hitLatency;
194    //assert(check());
195    return blk;
196}
197
198
199FALRUBlk*
200FALRU::findBlock(Addr addr) const
201{
202    Addr blkAddr = blkAlign(addr);
203    FALRUBlk* blk = hashLookup(blkAddr);
204
205    if (blk && blk->isValid()) {
206        assert(blk->tag == blkAddr);
207    } else {
208        blk = NULL;
209    }
210    return blk;
211}
212
213FALRUBlk*
214FALRU::findVictim(Addr addr, PacketList &writebacks)
215{
216    FALRUBlk * blk = tail;
217    assert(blk->inCache == 0);
218    moveToHead(blk);
219    tagHash.erase(blk->tag);
220    tagHash[blkAlign(addr)] = blk;
221    if (blk->isValid()) {
222        replacements[0]++;
223    } else {
224        tagsInUse++;
225        blk->isTouched = true;
226        if (!warmedUp && tagsInUse.value() >= warmupBound) {
227            warmedUp = true;
228            warmupCycle = curTick();
229        }
230    }
231    //assert(check());
232    return blk;
233}
234
235void
236FALRU::insertBlock(Addr addr, FALRU::BlkType *blk, int context_src)
237{
238}
239
240void
241FALRU::moveToHead(FALRUBlk *blk)
242{
243    int updateMask = blk->inCache ^ cacheMask;
244    for (unsigned i = 0; i < numCaches; i++){
245        if ((1<<i) & updateMask) {
246            cacheBoundaries[i]->inCache &= ~(1<<i);
247            cacheBoundaries[i] = cacheBoundaries[i]->prev;
248        } else if (cacheBoundaries[i] == blk) {
249            cacheBoundaries[i] = blk->prev;
250        }
251    }
252    blk->inCache = cacheMask;
253    if (blk != head) {
254        if (blk == tail){
255            assert(blk->next == NULL);
256            tail = blk->prev;
257            tail->next = NULL;
258        } else {
259            blk->prev->next = blk->next;
260            blk->next->prev = blk->prev;
261        }
262        blk->next = head;
263        blk->prev = NULL;
264        head->prev = blk;
265        head = blk;
266    }
267}
268
269bool
270FALRU::check()
271{
272    FALRUBlk* blk = head;
273    int size = 0;
274    int boundary = 1<<17;
275    int j = 0;
276    int flags = cacheMask;
277    while (blk) {
278        size += blkSize;
279        if (blk->inCache != flags) {
280            return false;
281        }
282        if (size == boundary && blk != tail) {
283            if (cacheBoundaries[j] != blk) {
284                return false;
285            }
286            flags &=~(1 << j);
287            boundary = boundary<<1;
288            ++j;
289        }
290        blk = blk->next;
291    }
292    return true;
293}
294
295void
296FALRU::clearLocks()
297{
298    for (int i = 0; i < numBlocks; i++){
299        blks[i].clearLoadLocks();
300    }
301}
302