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40 * Authors: Erik Hallnor
45 * Declaration of a base set associative tag store.
48 #ifndef __MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__
49 #define __MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__
55 #include "debug/CacheRepl.hh"
56 #include "mem/cache/base.hh"
57 #include "mem/cache/blk.hh"
58 #include "mem/cache/replacement_policies/base.hh"
59 #include "mem/cache/tags/base.hh"
60 #include "mem/cache/tags/cacheset.hh"
61 #include "mem/packet.hh"
62 #include "params/BaseSetAssoc.hh"
65 * A BaseSetAssoc cache tag store.
66 * @sa \ref gem5MemorySystem "gem5 Memory System"
68 * The BaseSetAssoc placement policy divides the cache into s sets of w
69 * cache lines (ways). A cache line is mapped onto a set, and can be placed
70 * into any of the ways of this set.
72 class BaseSetAssoc : public BaseTags
75 /** Typedef the block type used in this tag store. */
76 typedef CacheBlk BlkType;
77 /** Typedef the set type used in this tag store. */
78 typedef CacheSet<CacheBlk> SetType;
81 /** The associativity of the cache. */
83 /** The allocatable associativity of the cache (alloc mask). */
86 /** The cache blocks. */
87 std::vector<BlkType> blks;
89 /** The number of sets in the cache. */
90 const unsigned numSets;
92 /** Whether tags and data are accessed sequentially. */
93 const bool sequentialAccess;
95 /** The cache sets. */
96 std::vector<SetType> sets;
98 /** The amount to shift the address to get the set. */
100 /** The amount to shift the address to get the tag. */
102 /** Mask out all bits that aren't part of the set index. */
105 /** Replacement policy */
106 BaseReplacementPolicy *replacementPolicy;
109 /** Convenience typedef. */
110 typedef BaseSetAssocParams Params;
113 * Construct and initialize this tag store.
115 BaseSetAssoc(const Params *p);
120 virtual ~BaseSetAssoc() {};
123 * This function updates the tags when a block is invalidated but does
124 * not invalidate the block itself. It also updates the replacement data.
126 * @param blk The block to invalidate.
128 void invalidate(CacheBlk *blk) override;
131 * Find the cache block given set and way
132 * @param set The set of the block.
133 * @param way The way of the block.
134 * @return The cache block.
136 CacheBlk *findBlockBySetAndWay(int set, int way) const override;
139 * Access block and update replacement data. May not succeed, in which case
140 * nullptr is returned. This has all the implications of a cache
141 * access and should only be used as such. Returns the access latency as a
143 * @param addr The address to find.
144 * @param is_secure True if the target memory space is secure.
145 * @param lat The access latency.
146 * @return Pointer to the cache block if found.
148 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override
150 BlkType *blk = findBlock(addr, is_secure);
152 // Access all tags in parallel, hence one in each way. The data side
153 // either accesses all blocks in parallel, or one block sequentially on
154 // a hit. Sequential access with a miss doesn't access data.
155 tagAccesses += allocAssoc;
156 if (sequentialAccess) {
157 if (blk != nullptr) {
161 dataAccesses += allocAssoc;
164 if (blk != nullptr) {
167 // Check if the block to be accessed is available. If not,
168 // apply the accessLatency on top of block->whenReady.
169 if (blk->whenReady > curTick() &&
170 cache->ticksToCycles(blk->whenReady - curTick()) >
172 lat = cache->ticksToCycles(blk->whenReady - curTick()) +
176 // Update number of references to accessed block
179 // Update replacement data of accessed block
180 replacementPolicy->touch(blk->replacementData);
190 * Finds the given address in the cache, do not update replacement data.
191 * i.e. This is a no-side-effect find of a block.
192 * @param addr The address to find.
193 * @param is_secure True if the target memory space is secure.
194 * @param asid The address space ID.
195 * @return Pointer to the cache block if found.
197 CacheBlk* findBlock(Addr addr, bool is_secure) const override;
200 * Find replacement victim based on address.
202 * @param addr Address to find a victim for.
203 * @return Cache block to be replaced.
205 CacheBlk* findVictim(Addr addr) override
207 // Get possible locations for the victim block
208 std::vector<CacheBlk*> locations = getPossibleLocations(addr);
210 // Choose replacement victim from replacement candidates
211 CacheBlk* victim = static_cast<CacheBlk*>(replacementPolicy->getVictim(
212 std::vector<ReplaceableEntry*>(
213 locations.begin(), locations.end())));
215 DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
216 victim->set, victim->way);
222 * Find all possible block locations for insertion and replacement of
223 * an address. Should be called immediately before ReplacementPolicy's
224 * findVictim() not to break cache resizing.
225 * Returns blocks in all ways belonging to the set of the address.
227 * @param addr The addr to a find possible locations for.
228 * @return The possible locations.
230 const std::vector<CacheBlk*> getPossibleLocations(Addr addr)
232 return sets[extractSet(addr)].blks;
236 * Insert the new block into the cache and update replacement data.
238 * @param pkt Packet holding the address to update
239 * @param blk The block to update.
241 void insertBlock(PacketPtr pkt, CacheBlk *blk) override
244 BaseTags::insertBlock(pkt, blk);
246 // Update replacement policy
247 replacementPolicy->reset(blk->replacementData);
251 * Limit the allocation for the cache ways.
252 * @param ways The maximum number of ways available for replacement.
254 virtual void setWayAllocationMax(int ways) override
256 fatal_if(ways < 1, "Allocation limit must be greater than zero");
261 * Get the way allocation mask limit.
262 * @return The maximum number of ways available for replacement.
264 virtual int getWayAllocationMax() const override
270 * Generate the tag from the given address.
271 * @param addr The address to get the tag from.
272 * @return The tag of the address.
274 Addr extractTag(Addr addr) const override
276 return (addr >> tagShift);
280 * Calculate the set index from the address.
281 * @param addr The address to get the set from.
282 * @return The set index of the address.
284 int extractSet(Addr addr) const override
286 return ((addr >> setShift) & setMask);
290 * Regenerate the block address from the tag and set.
292 * @param block The block.
293 * @return the block address.
295 Addr regenerateBlkAddr(const CacheBlk* blk) const override
297 return ((blk->tag << tagShift) | ((Addr)blk->set << setShift));
301 * Called at end of simulation to complete average block reference stats.
303 void cleanupRefs() override;
306 * Print all tags used
308 std::string print() const override;
311 * Called prior to dumping stats to compute task occupancy
313 void computeStats() override;
316 * Visit each block in the tag store and apply a visitor to the
319 * The visitor should be a function (or object that behaves like a
320 * function) that takes a cache block reference as its parameter
321 * and returns a bool. A visitor can request the traversal to be
322 * stopped by returning false, returning true causes it to be
323 * called for the next block in the tag store.
325 * \param visitor Visitor to call on each block.
327 void forEachBlk(CacheBlkVisitor &visitor) override {
328 for (CacheBlk& blk : blks) {
335 #endif //__MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__