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40 * Authors: Erik Hallnor
46 * Declaration of a fully associative LRU tag store.
49 #ifndef __MEM_CACHE_TAGS_FA_LRU_HH__
50 #define __MEM_CACHE_TAGS_FA_LRU_HH__
55 #include <unordered_map>
57 #include "base/bitfield.hh"
58 #include "base/intmath.hh"
59 #include "base/logging.hh"
60 #include "base/statistics.hh"
61 #include "base/types.hh"
62 #include "mem/cache/blk.hh"
63 #include "mem/cache/tags/base.hh"
64 #include "mem/packet.hh"
65 #include "params/FALRU.hh"
67 // Uncomment to enable sanity checks for the FALRU cache and the
68 // TrackedCaches class
71 class ReplaceableEntry;
73 // A bitmask of the caches we are keeping track of. Currently the
74 // lowest bit is the smallest cache we are tracking, as it is
75 // specified by the corresponding parameter. The rest of the bits are
76 // for exponentially growing cache sizes.
77 typedef uint32_t CachesMask;
80 * A fully associative cache block.
82 class FALRUBlk : public CacheBlk
85 /** The previous block in LRU order. */
87 /** The next block in LRU order. */
90 /** A bit mask of the caches that fit this block. */
91 CachesMask inCachesMask;
95 * A fully associative LRU cache. Keeps statistics for accesses to a number of
96 * cache sizes at once.
98 class FALRU : public BaseTags
101 /** Typedef the block type used in this class. */
102 typedef FALRUBlk BlkType;
105 /** The cache blocks. */
108 /** The MRU block. */
110 /** The LRU block. */
113 /** Hash table type mapping addresses to cache block pointers. */
114 typedef std::unordered_map<Addr, FALRUBlk *, std::hash<Addr> > hash_t;
115 /** Iterator into the address hash table. */
116 typedef hash_t::const_iterator tagIterator;
118 /** The address hash table. */
122 * Find the cache block for the given address.
123 * @param addr The address to find.
124 * @return The cache block of the address, if any.
126 FALRUBlk * hashLookup(Addr addr) const;
129 * Move a cache block to the MRU position.
131 * @param blk The block to promote.
133 void moveToHead(FALRUBlk *blk);
136 * Move a cache block to the LRU position.
138 * @param blk The block to demote.
140 void moveToTail(FALRUBlk *blk);
143 typedef FALRUParams Params;
146 * Construct and initialize this cache tagstore.
148 FALRU(const Params *p);
152 * Register the stats for this object.
154 void regStats() override;
157 * Invalidate a cache block.
158 * @param blk The block to invalidate.
160 void invalidate(CacheBlk *blk) override;
163 * Access block and update replacement data. May not succeed, in which
164 * case nullptr pointer is returned. This has all the implications of a
165 * cache access and should only be used as such.
166 * Returns the access latency and inCachesMask flags as a side effect.
167 * @param addr The address to look for.
168 * @param is_secure True if the target memory space is secure.
169 * @param lat The latency of the access.
170 * @param in_cache_mask Mask indicating the caches in which the blk fits.
171 * @return Pointer to the cache block.
173 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat,
174 CachesMask *in_cache_mask);
177 * Just a wrapper of above function to conform with the base interface.
179 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override;
182 * Find the block in the cache, do not update the replacement data.
183 * @param addr The address to look for.
184 * @param is_secure True if the target memory space is secure.
185 * @param asid The address space ID.
186 * @return Pointer to the cache block.
188 CacheBlk* findBlock(Addr addr, bool is_secure) const override;
191 * Find a block given set and way.
193 * @param set The set of the block.
194 * @param way The way of the block.
197 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override;
200 * Find replacement victim based on address. The list of evicted blocks
201 * only contains the victim.
203 * @param addr Address to find a victim for.
204 * @param is_secure True if the target memory space is secure.
205 * @param evict_blks Cache blocks to be evicted.
206 * @return Cache block to be replaced.
208 CacheBlk* findVictim(Addr addr, const bool is_secure,
209 std::vector<CacheBlk*>& evict_blks) const override;
212 * Insert the new block into the cache and update replacement data.
214 * @param pkt Packet holding the address to update
215 * @param blk The block to update.
217 void insertBlock(const PacketPtr pkt, CacheBlk *blk) override;
220 * Generate the tag from the addres. For fully associative this is just the
222 * @param addr The address to get the tag from.
225 Addr extractTag(Addr addr) const override
227 return blkAlign(addr);
231 * Regenerate the block address from the tag.
233 * @param block The block.
234 * @return the block address.
236 Addr regenerateBlkAddr(const CacheBlk* blk) const override
241 void forEachBlk(std::function<void(CacheBlk &)> visitor) override {
242 for (int i = 0; i < numBlocks; i++) {
247 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override {
248 for (int i = 0; i < numBlocks; i++) {
249 if (visitor(blks[i])) {
258 * Mechanism that allows us to simultaneously collect miss
259 * statistics for multiple caches. Currently, we keep track of
260 * caches from a set minimum size of interest up to the actual
266 CacheTracking(unsigned min_size, unsigned max_size,
268 : blkSize(block_size),
269 minTrackedSize(min_size),
270 numTrackedCaches(max_size > min_size ?
271 floorLog2(max_size) - floorLog2(min_size) : 0),
272 inAllCachesMask(mask(numTrackedCaches)),
273 boundaries(new FALRUBlk *[numTrackedCaches])
275 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8,
276 "Not enough bits (%s) in type CachesMask type to keep "
277 "track of %d caches\n", sizeof(CachesMask),
287 * Initialiaze cache blocks and the tracking mechanism
289 * All blocks in the cache need to be initialized once.
291 * @param blk the MRU block
292 * @param blk the LRU block
294 void init(FALRUBlk *head, FALRUBlk *tail);
297 * Update boundaries as a block will be moved to the MRU.
299 * For all caches that didn't fit the block before moving it,
300 * we move their boundaries one block closer to the MRU. We
301 * also update InCacheMasks as neccessary.
303 * @param blk the block that will be moved to the head
305 void moveBlockToHead(FALRUBlk *blk);
308 * Update boundaries as a block will be moved to the LRU.
310 * For all caches that fitted the block before moving it, we
311 * move their boundaries one block closer to the LRU. We
312 * also update InCacheMasks as neccessary.
314 * @param blk the block that will be moved to the head
316 void moveBlockToTail(FALRUBlk *blk);
319 * Notify of a block access.
321 * This should be called every time a block is accessed and it
322 * updates statistics. If the input block is nullptr then we
323 * treat the access as a miss. The block's InCacheMask
324 * determines the caches in which the block fits.
326 * @param blk the block to record the access for
328 void recordAccess(FALRUBlk *blk);
331 * Check that the tracking mechanism is in consistent state.
333 * Iterate from the head (MRU) to the tail (LRU) of the list
334 * of blocks and assert the inCachesMask and the boundaries
335 * are in consistent state.
337 * @param head the MRU block of the actual cache
338 * @param head the LRU block of the actual cache
340 void check(FALRUBlk *head, FALRUBlk *tail);
343 * Register the stats for this object.
345 void regStats(std::string name);
348 /** The size of the cache block */
349 const unsigned blkSize;
350 /** The smallest cache we are tracking */
351 const unsigned minTrackedSize;
352 /** The number of different size caches being tracked. */
353 const int numTrackedCaches;
354 /** A mask for all cache being tracked. */
355 const CachesMask inAllCachesMask;
356 /** Array of pointers to blocks at the cache boundaries. */
357 FALRUBlk** boundaries;
361 * @defgroup FALRUStats Fully Associative LRU specific statistics
362 * The FA lru stack lets us track multiple cache sizes at once. These
363 * statistics track the hits and misses for different cache sizes.
367 /** Hits in each cache */
369 /** Misses in each cache */
370 Stats::Vector misses;
371 /** Total number of accesses */
372 Stats::Scalar accesses;
378 CacheTracking cacheTracking;
381 #endif // __MEM_CACHE_TAGS_FA_LRU_HH__