2 * Copyright (c) 2003-2005 The Regents of The University of Michigan
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16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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28 * Authors: Erik Hallnor
33 * Definitions of LRU tag store.
38 #include "mem/cache/base_cache.hh"
39 #include "base/intmath.hh"
40 #include "mem/cache/tags/lru.hh"
41 #include "sim/core.hh"
46 CacheSet::findBlk(Addr tag
) const
48 for (int i
= 0; i
< assoc
; ++i
) {
49 if (blks
[i
]->tag
== tag
&& blks
[i
]->isValid()) {
58 CacheSet::moveToHead(LRUBlk
*blk
)
60 // nothing to do if blk is already head
64 // write 'next' block into blks[i], moving up from MRU toward LRU
65 // until we overwrite the block we moved to head.
67 // start by setting up to write 'blk' into blks[0]
73 // swap blks[i] and next
74 LRUBlk
*tmp
= blks
[i
];
78 } while (next
!= blk
);
82 // create and initialize a LRU/MRU cache structure
83 LRU::LRU(int _numSets
, int _blkSize
, int _assoc
, int _hit_latency
) :
84 numSets(_numSets
), blkSize(_blkSize
), assoc(_assoc
), hitLatency(_hit_latency
)
87 if (blkSize
< 4 || !isPowerOf2(blkSize
)) {
88 fatal("Block size must be at least 4 and a power of 2");
90 if (numSets
<= 0 || !isPowerOf2(numSets
)) {
91 fatal("# of sets must be non-zero and a power of 2");
94 fatal("associativity must be greater than zero");
96 if (hitLatency
<= 0) {
97 fatal("access latency must be greater than zero");
103 blkMask
= blkSize
- 1;
104 setShift
= floorLog2(blkSize
);
105 setMask
= numSets
- 1;
106 tagShift
= setShift
+ floorLog2(numSets
);
108 /** @todo Make warmup percentage a parameter. */
109 warmupBound
= numSets
* assoc
;
111 sets
= new CacheSet
[numSets
];
112 blks
= new LRUBlk
[numSets
* assoc
];
113 // allocate data storage in one big chunk
114 dataBlks
= new uint8_t[numSets
*assoc
*blkSize
];
116 blkIndex
= 0; // index into blks array
117 for (i
= 0; i
< numSets
; ++i
) {
118 sets
[i
].assoc
= assoc
;
120 sets
[i
].blks
= new LRUBlk
*[assoc
];
122 // link in the data blocks
123 for (j
= 0; j
< assoc
; ++j
) {
124 // locate next cache block
125 blk
= &blks
[blkIndex
];
126 blk
->data
= &dataBlks
[blkSize
*blkIndex
];
129 // invalidate new cache block
132 //EGH Fix Me : do we need to initialize blk?
134 // Setting the tag to j is just to prevent long chains in the hash
135 // table; won't matter because the block is invalid
138 blk
->isTouched
= false;
153 // probe cache for presence of given block.
155 LRU::probe(Addr addr
) const
157 // return(findBlock(Read, addr, asid) != 0);
158 Addr tag
= extractTag(addr
);
159 unsigned myset
= extractSet(addr
);
161 LRUBlk
*blk
= sets
[myset
].findBlk(tag
);
163 return (blk
!= NULL
); // true if in cache
167 LRU::findBlock(Addr addr
, int &lat
)
169 Addr tag
= extractTag(addr
);
170 unsigned set
= extractSet(addr
);
171 LRUBlk
*blk
= sets
[set
].findBlk(tag
);
174 // move this block to head of the MRU list
175 sets
[set
].moveToHead(blk
);
176 DPRINTF(CacheRepl
, "set %x: moving blk %x to MRU\n",
177 set
, regenerateBlkAddr(tag
, set
));
178 if (blk
->whenReady
> curTick
179 && blk
->whenReady
- curTick
> hitLatency
) {
180 lat
= blk
->whenReady
- curTick
;
190 LRU::findBlock(Addr addr
) const
192 Addr tag
= extractTag(addr
);
193 unsigned set
= extractSet(addr
);
194 LRUBlk
*blk
= sets
[set
].findBlk(tag
);
199 LRU::findReplacement(Addr addr
, PacketList
&writebacks
)
201 unsigned set
= extractSet(addr
);
202 // grab a replacement candidate
203 LRUBlk
*blk
= sets
[set
].blks
[assoc
-1];
204 sets
[set
].moveToHead(blk
);
205 if (blk
->isValid()) {
207 totalRefs
+= blk
->refCount
;
211 DPRINTF(CacheRepl
, "set %x: selecting blk %x for replacement\n",
212 set
, regenerateBlkAddr(blk
->tag
, set
));
213 } else if (!blk
->isTouched
) {
215 blk
->isTouched
= true;
216 if (!warmedUp
&& tagsInUse
.value() >= warmupBound
) {
218 warmupCycle
= curTick
;
226 LRU::invalidateBlk(LRU::BlkType
*blk
)
230 blk
->isTouched
= false;
231 blk
->clearLoadLocks();
239 for (int i
= 0; i
< numSets
*assoc
; ++i
) {
240 if (blks
[i
].isValid()) {
241 totalRefs
+= blks
[i
].refCount
;