fa_lru.cc revision 7823:dac01f14f20f 
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, unsigned 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
101void
102FALRU::regStats(const string &name)
103{
104    using namespace Stats;
105    BaseTags::regStats(name);
106    hits
107        .init(numCaches+1)
108        .name(name + ".falru_hits")
109        .desc("The number of hits in each cache size.")
110        ;
111    misses
112        .init(numCaches+1)
113        .name(name + ".falru_misses")
114        .desc("The number of misses in each cache size.")
115        ;
116    accesses
117        .name(name + ".falru_accesses")
118        .desc("The number of accesses to the FA LRU cache.")
119        ;
120
121    for (unsigned i = 0; i <= numCaches; ++i) {
122        stringstream size_str;
123        if (i < 3){
124            size_str << (1<<(i+7)) <<"K";
125        } else {
126            size_str << (1<<(i-3)) <<"M";
127        }
128
129        hits.subname(i, size_str.str());
130        hits.subdesc(i, "Hits in a " + size_str.str() +" cache");
131        misses.subname(i, size_str.str());
132        misses.subdesc(i, "Misses in a " + size_str.str() +" cache");
133    }
134}
135
136FALRUBlk *
137FALRU::hashLookup(Addr addr) const
138{
139    tagIterator iter = tagHash.find(addr);
140    if (iter != tagHash.end()) {
141        return (*iter).second;
142    }
143    return NULL;
144}
145
146void
147FALRU::invalidateBlk(FALRU::BlkType *blk)
148{
149    if (blk) {
150        blk->status = 0;
151        blk->isTouched = false;
152        tagsInUse--;
153    }
154}
155
156FALRUBlk*
157FALRU::accessBlock(Addr addr, int &lat, int context_src, int *inCache)
158{
159    accesses++;
160    int tmp_in_cache = 0;
161    Addr blkAddr = blkAlign(addr);
162    FALRUBlk* blk = hashLookup(blkAddr);
163
164    if (blk && blk->isValid()) {
165        assert(blk->tag == blkAddr);
166        tmp_in_cache = blk->inCache;
167        for (unsigned i = 0; i < numCaches; i++) {
168            if (1<<i & blk->inCache) {
169                hits[i]++;
170            } else {
171                misses[i]++;
172            }
173        }
174        hits[numCaches]++;
175        if (blk != head){
176            moveToHead(blk);
177        }
178    } else {
179        blk = NULL;
180        for (unsigned i = 0; i <= numCaches; ++i) {
181            misses[i]++;
182        }
183    }
184    if (inCache) {
185        *inCache = tmp_in_cache;
186    }
187
188    lat = hitLatency;
189    //assert(check());
190    return blk;
191}
192
193
194FALRUBlk*
195FALRU::findBlock(Addr addr) const
196{
197    Addr blkAddr = blkAlign(addr);
198    FALRUBlk* blk = hashLookup(blkAddr);
199
200    if (blk && blk->isValid()) {
201        assert(blk->tag == blkAddr);
202    } else {
203        blk = NULL;
204    }
205    return blk;
206}
207
208FALRUBlk*
209FALRU::findVictim(Addr addr, PacketList &writebacks)
210{
211    FALRUBlk * blk = tail;
212    assert(blk->inCache == 0);
213    moveToHead(blk);
214    tagHash.erase(blk->tag);
215    tagHash[blkAlign(addr)] = blk;
216    if (blk->isValid()) {
217        replacements[0]++;
218    } else {
219        tagsInUse++;
220        blk->isTouched = true;
221        if (!warmedUp && tagsInUse.value() >= warmupBound) {
222            warmedUp = true;
223            warmupCycle = curTick();
224        }
225    }
226    //assert(check());
227    return blk;
228}
229
230void
231FALRU::insertBlock(Addr addr, FALRU::BlkType *blk, int context_src)
232{
233}
234
235void
236FALRU::moveToHead(FALRUBlk *blk)
237{
238    int updateMask = blk->inCache ^ cacheMask;
239    for (unsigned i = 0; i < numCaches; i++){
240        if ((1<<i) & updateMask) {
241            cacheBoundaries[i]->inCache &= ~(1<<i);
242            cacheBoundaries[i] = cacheBoundaries[i]->prev;
243        } else if (cacheBoundaries[i] == blk) {
244            cacheBoundaries[i] = blk->prev;
245        }
246    }
247    blk->inCache = cacheMask;
248    if (blk != head) {
249        if (blk == tail){
250            assert(blk->next == NULL);
251            tail = blk->prev;
252            tail->next = NULL;
253        } else {
254            blk->prev->next = blk->next;
255            blk->next->prev = blk->prev;
256        }
257        blk->next = head;
258        blk->prev = NULL;
259        head->prev = blk;
260        head = blk;
261    }
262}
263
264bool
265FALRU::check()
266{
267    FALRUBlk* blk = head;
268    int size = 0;
269    int boundary = 1<<17;
270    int j = 0;
271    int flags = cacheMask;
272    while (blk) {
273        size += blkSize;
274        if (blk->inCache != flags) {
275            return false;
276        }
277        if (size == boundary && blk != tail) {
278            if (cacheBoundaries[j] != blk) {
279                return false;
280            }
281            flags &=~(1 << j);
282            boundary = boundary<<1;
283            ++j;
284        }
285        blk = blk->next;
286    }
287    return true;
288}
289
290void
291FALRU::clearLocks()
292{
293    for (int i = 0; i < numBlocks; i++){
294        blks[i].clearLoadLocks();
295    }
296}
297