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33 * Definitions of LRU tag store for a partitioned cache.
38 #include "mem/cache/base_cache.hh"
39 #include "base/intmath.hh"
40 #include "mem/cache/tags/split_lru.hh"
41 #include "sim/core.hh"
46 SplitCacheSet::findBlk(Addr tag
) const
48 for (int i
= 0; i
< assoc
; ++i
) {
49 if (blks
[i
]->tag
== tag
&& blks
[i
]->isValid()) {
58 SplitCacheSet::moveToHead(SplitBlk
*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 SplitBlk
*tmp
= blks
[i
];
78 } while (next
!= blk
);
82 // create and initialize a LRU/MRU cache structure
83 SplitLRU::SplitLRU(int _numSets
, int _blkSize
, int _assoc
, int _hit_latency
, int _part
) :
84 numSets(_numSets
), blkSize(_blkSize
), assoc(_assoc
), hitLatency(_hit_latency
), part(_part
)
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 SplitCacheSet
[numSets
];
112 blks
= new SplitBlk
[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 SplitBlk
*[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;
147 SplitLRU::~SplitLRU()
155 SplitLRU::regStats(const std::string
&name
)
157 BaseTags::regStats(name
);
160 .name(name
+ ".hits")
161 .desc("number of hits on this partition")
166 .name(name
+ ".misses")
167 .desc("number of misses in this partition")
172 // probe cache for presence of given block.
174 SplitLRU::probe(Addr addr
) const
176 // return(findBlock(Read, addr, asid) != 0);
177 Addr tag
= extractTag(addr
);
178 unsigned myset
= extractSet(addr
);
180 SplitBlk
*blk
= sets
[myset
].findBlk(tag
);
182 return (blk
!= NULL
); // true if in cache
186 SplitLRU::findBlock(Addr addr
, int &lat
)
188 Addr tag
= extractTag(addr
);
189 unsigned set
= extractSet(addr
);
190 SplitBlk
*blk
= sets
[set
].findBlk(tag
);
193 // move this block to head of the MRU list
194 sets
[set
].moveToHead(blk
);
195 if (blk
->whenReady
> curTick
&& blk
->whenReady
- curTick
> hitLatency
){
196 lat
= blk
->whenReady
- curTick
;
207 SplitLRU::findBlock(Addr addr
) const
209 Addr tag
= extractTag(addr
);
210 unsigned set
= extractSet(addr
);
211 SplitBlk
*blk
= sets
[set
].findBlk(tag
);
216 SplitLRU::findReplacement(PacketPtr
&pkt
, PacketList
&writebacks
,
217 BlkList
&compress_blocks
)
219 unsigned set
= extractSet(pkt
->getAddr());
220 // grab a replacement candidate
221 SplitBlk
*blk
= sets
[set
].blks
[assoc
-1];
222 sets
[set
].moveToHead(blk
);
223 if (blk
->isValid()) {
225 totalRefs
+= blk
->refCount
;
228 } else if (!blk
->isTouched
) {
230 blk
->isTouched
= true;
231 if (!warmedUp
&& tagsInUse
.value() >= warmupBound
) {
233 warmupCycle
= curTick
;
243 SplitLRU::invalidateBlk(SplitLRU::BlkType
*blk
)
247 blk
->isTouched
= false;
253 SplitLRU::cleanupRefs()
255 for (int i
= 0; i
< numSets
*assoc
; ++i
) {
256 if (blks
[i
].isValid()) {
257 totalRefs
+= blks
[i
].refCount
;