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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>
58 #include "base/bitfield.hh"
59 #include "base/intmath.hh"
60 #include "base/logging.hh"
61 #include "base/statistics.hh"
62 #include "base/types.hh"
63 #include "mem/cache/blk.hh"
64 #include "mem/cache/tags/base.hh"
65 #include "params/FALRU.hh"
67 // Uncomment to enable sanity checks for the FALRU cache and the
68 // TrackedCaches class
72 class ReplaceableEntry;
74 // A bitmask of the caches we are keeping track of. Currently the
75 // lowest bit is the smallest cache we are tracking, as it is
76 // specified by the corresponding parameter. The rest of the bits are
77 // for exponentially growing cache sizes.
78 typedef uint32_t CachesMask;
81 * A fully associative cache block.
83 class FALRUBlk : public CacheBlk
86 FALRUBlk() : CacheBlk(), prev(nullptr), next(nullptr), inCachesMask(0) {}
88 /** The previous block in LRU order. */
90 /** The next block in LRU order. */
93 /** A bit mask of the caches that fit this block. */
94 CachesMask inCachesMask;
97 * Pretty-print inCachesMask and other CacheBlk information.
99 * @return string with basic state information
101 std::string print() const override;
105 * A fully associative LRU cache. Keeps statistics for accesses to a number of
106 * cache sizes at once.
108 class FALRU : public BaseTags
111 /** Typedef the block type used in this class. */
112 typedef FALRUBlk BlkType;
115 /** The cache blocks. */
118 /** The MRU block. */
120 /** The LRU block. */
123 /** Hash table type mapping addresses to cache block pointers. */
126 template <class T1, class T2>
127 std::size_t operator()(const std::pair<T1, T2> &p) const
129 return std::hash<T1>()(p.first) ^ std::hash<T2>()(p.second);
132 typedef std::pair<Addr, bool> TagHashKey;
133 typedef std::unordered_map<TagHashKey, FALRUBlk *, PairHash> TagHash;
135 /** The address hash table. */
139 * Move a cache block to the MRU position.
141 * @param blk The block to promote.
143 void moveToHead(FALRUBlk *blk);
146 * Move a cache block to the LRU position.
148 * @param blk The block to demote.
150 void moveToTail(FALRUBlk *blk);
153 typedef FALRUParams Params;
156 * Construct and initialize this cache tagstore.
158 FALRU(const Params *p);
162 * Initialize blocks and set the parent cache back pointer.
164 * @param _cache Pointer to parent cache.
166 void init(BaseCache *_cache) override;
169 * Register the stats for this object.
171 void regStats() override;
174 * Invalidate a cache block.
175 * @param blk The block to invalidate.
177 void invalidate(CacheBlk *blk) override;
180 * Access block and update replacement data. May not succeed, in which
181 * case nullptr pointer is returned. This has all the implications of a
182 * cache access and should only be used as such.
183 * Returns the access latency and inCachesMask flags as a side effect.
184 * @param addr The address to look for.
185 * @param is_secure True if the target memory space is secure.
186 * @param lat The latency of the access.
187 * @param in_cache_mask Mask indicating the caches in which the blk fits.
188 * @return Pointer to the cache block.
190 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat,
191 CachesMask *in_cache_mask);
194 * Just a wrapper of above function to conform with the base interface.
196 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override;
199 * Find the block in the cache, do not update the replacement data.
200 * @param addr The address to look for.
201 * @param is_secure True if the target memory space is secure.
202 * @param asid The address space ID.
203 * @return Pointer to the cache block.
205 CacheBlk* findBlock(Addr addr, bool is_secure) const override;
208 * Find a block given set and way.
210 * @param set The set of the block.
211 * @param way The way of the block.
214 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override;
217 * Find replacement victim based on address. The list of evicted blocks
218 * only contains the victim.
220 * @param addr Address to find a victim for.
221 * @param is_secure True if the target memory space is secure.
222 * @param evict_blks Cache blocks to be evicted.
223 * @return Cache block to be replaced.
225 CacheBlk* findVictim(Addr addr, const bool is_secure,
226 std::vector<CacheBlk*>& evict_blks) const override;
229 * Insert the new block into the cache and update replacement data.
231 * @param addr Address of the block.
232 * @param is_secure Whether the block is in secure space or not.
233 * @param src_master_ID The source requestor ID.
234 * @param task_ID The new task ID.
235 * @param blk The block to update.
237 void insertBlock(const Addr addr, const bool is_secure,
238 const int src_master_ID, const uint32_t task_ID,
239 CacheBlk *blk) override;
242 * Generate the tag from the addres. For fully associative this is just the
244 * @param addr The address to get the tag from.
247 Addr extractTag(Addr addr) const override
249 return blkAlign(addr);
253 * Regenerate the block address from the tag.
255 * @param block The block.
256 * @return the block address.
258 Addr regenerateBlkAddr(const CacheBlk* blk) const override
263 void forEachBlk(std::function<void(CacheBlk &)> visitor) override {
264 for (int i = 0; i < numBlocks; i++) {
269 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override {
270 for (int i = 0; i < numBlocks; i++) {
271 if (visitor(blks[i])) {
280 * Mechanism that allows us to simultaneously collect miss
281 * statistics for multiple caches. Currently, we keep track of
282 * caches from a set minimum size of interest up to the actual
288 CacheTracking(unsigned min_size, unsigned max_size,
290 : blkSize(block_size),
291 minTrackedSize(min_size),
292 numTrackedCaches(max_size > min_size ?
293 floorLog2(max_size) - floorLog2(min_size) : 0),
294 inAllCachesMask(mask(numTrackedCaches)),
295 boundaries(numTrackedCaches)
297 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8,
298 "Not enough bits (%s) in type CachesMask type to keep "
299 "track of %d caches\n", sizeof(CachesMask),
304 * Initialiaze cache blocks and the tracking mechanism
306 * All blocks in the cache need to be initialized once.
308 * @param blk the MRU block
309 * @param blk the LRU block
311 void init(FALRUBlk *head, FALRUBlk *tail);
314 * Update boundaries as a block will be moved to the MRU.
316 * For all caches that didn't fit the block before moving it,
317 * we move their boundaries one block closer to the MRU. We
318 * also update InCacheMasks as neccessary.
320 * @param blk the block that will be moved to the head
322 void moveBlockToHead(FALRUBlk *blk);
325 * Update boundaries as a block will be moved to the LRU.
327 * For all caches that fitted the block before moving it, we
328 * move their boundaries one block closer to the LRU. We
329 * also update InCacheMasks as neccessary.
331 * @param blk the block that will be moved to the head
333 void moveBlockToTail(FALRUBlk *blk);
336 * Notify of a block access.
338 * This should be called every time a block is accessed and it
339 * updates statistics. If the input block is nullptr then we
340 * treat the access as a miss. The block's InCacheMask
341 * determines the caches in which the block fits.
343 * @param blk the block to record the access for
345 void recordAccess(FALRUBlk *blk);
348 * Check that the tracking mechanism is in consistent state.
350 * Iterate from the head (MRU) to the tail (LRU) of the list
351 * of blocks and assert the inCachesMask and the boundaries
352 * are in consistent state.
354 * @param head the MRU block of the actual cache
355 * @param head the LRU block of the actual cache
357 void check(const FALRUBlk *head, const FALRUBlk *tail) const;
360 * Register the stats for this object.
362 void regStats(std::string name);
365 /** The size of the cache block */
366 const unsigned blkSize;
367 /** The smallest cache we are tracking */
368 const unsigned minTrackedSize;
369 /** The number of different size caches being tracked. */
370 const int numTrackedCaches;
371 /** A mask for all cache being tracked. */
372 const CachesMask inAllCachesMask;
373 /** Array of pointers to blocks at the cache boundaries. */
374 std::vector<FALRUBlk*> boundaries;
378 * @defgroup FALRUStats Fully Associative LRU specific statistics
379 * The FA lru stack lets us track multiple cache sizes at once. These
380 * statistics track the hits and misses for different cache sizes.
384 /** Hits in each cache */
386 /** Misses in each cache */
387 Stats::Vector misses;
388 /** Total number of accesses */
389 Stats::Scalar accesses;
395 CacheTracking cacheTracking;
398 #endif // __MEM_CACHE_TAGS_FA_LRU_HH__