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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 "base/logging.hh"
56 #include "base/types.hh"
57 #include "debug/CacheRepl.hh"
58 #include "mem/cache/base.hh"
59 #include "mem/cache/blk.hh"
60 #include "mem/cache/replacement_policies/base.hh"
61 #include "mem/cache/tags/base.hh"
62 #include "mem/cache/tags/cacheset.hh"
63 #include "mem/packet.hh"
64 #include "params/BaseSetAssoc.hh"
67 * A BaseSetAssoc cache tag store.
68 * @sa \ref gem5MemorySystem "gem5 Memory System"
70 * The BaseSetAssoc placement policy divides the cache into s sets of w
71 * cache lines (ways). A cache line is mapped onto a set, and can be placed
72 * into any of the ways of this set.
74 class BaseSetAssoc : public BaseTags
77 /** Typedef the block type used in this tag store. */
78 typedef CacheBlk BlkType;
79 /** Typedef the set type used in this tag store. */
80 typedef CacheSet<CacheBlk> SetType;
83 /** The associativity of the cache. */
85 /** The allocatable associativity of the cache (alloc mask). */
88 /** The cache blocks. */
89 std::vector<BlkType> blks;
91 /** The number of sets in the cache. */
92 const unsigned numSets;
94 /** Whether tags and data are accessed sequentially. */
95 const bool sequentialAccess;
97 /** The cache sets. */
98 std::vector<SetType> sets;
100 /** The amount to shift the address to get the set. */
102 /** The amount to shift the address to get the tag. */
104 /** Mask out all bits that aren't part of the set index. */
107 /** Replacement policy */
108 BaseReplacementPolicy *replacementPolicy;
111 /** Convenience typedef. */
112 typedef BaseSetAssocParams Params;
115 * Construct and initialize this tag store.
117 BaseSetAssoc(const Params *p);
122 virtual ~BaseSetAssoc() {};
125 * This function updates the tags when a block is invalidated. It also
126 * updates the replacement data.
128 * @param blk The block to invalidate.
130 void invalidate(CacheBlk *blk) override;
133 * Access block and update replacement data. May not succeed, in which case
134 * nullptr is returned. This has all the implications of a cache
135 * access and should only be used as such. Returns the access latency as a
137 * @param addr The address to find.
138 * @param is_secure True if the target memory space is secure.
139 * @param lat The access latency.
140 * @return Pointer to the cache block if found.
142 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override
144 BlkType *blk = findBlock(addr, is_secure);
146 // Access all tags in parallel, hence one in each way. The data side
147 // either accesses all blocks in parallel, or one block sequentially on
148 // a hit. Sequential access with a miss doesn't access data.
149 tagAccesses += allocAssoc;
150 if (sequentialAccess) {
151 if (blk != nullptr) {
155 dataAccesses += allocAssoc;
158 if (blk != nullptr) {
161 // Check if the block to be accessed is available. If not,
162 // apply the accessLatency on top of block->whenReady.
163 if (blk->whenReady > curTick() &&
164 cache->ticksToCycles(blk->whenReady - curTick()) >
166 lat = cache->ticksToCycles(blk->whenReady - curTick()) +
170 // Update number of references to accessed block
173 // Update replacement data of accessed block
174 replacementPolicy->touch(blk->replacementData);
184 * Finds the given address in the cache, do not update replacement data.
185 * i.e. This is a no-side-effect find of a block.
186 * @param addr The address to find.
187 * @param is_secure True if the target memory space is secure.
188 * @param asid The address space ID.
189 * @return Pointer to the cache block if found.
191 CacheBlk* findBlock(Addr addr, bool is_secure) const override;
194 * Find a block given set and way.
196 * @param set The set of the block.
197 * @param way The way of the block.
200 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override;
203 * Find replacement victim based on address. The list of evicted blocks
204 * only contains the victim.
206 * @param addr Address to find a victim for.
207 * @param is_secure True if the target memory space is secure.
208 * @param evict_blks Cache blocks to be evicted.
209 * @return Cache block to be replaced.
211 CacheBlk* findVictim(Addr addr, const bool is_secure,
212 std::vector<CacheBlk*>& evict_blks) const override
214 // Get possible locations for the victim block
215 std::vector<CacheBlk*> locations = getPossibleLocations(addr);
217 // Choose replacement victim from replacement candidates
218 CacheBlk* victim = static_cast<CacheBlk*>(replacementPolicy->getVictim(
219 std::vector<ReplaceableEntry*>(
220 locations.begin(), locations.end())));
222 // There is only one eviction for this replacement
223 evict_blks.push_back(victim);
225 DPRINTF(CacheRepl, "set %x, way %x: selecting blk for replacement\n",
226 victim->set, victim->way);
232 * Find all possible block locations for insertion and replacement of
233 * an address. Should be called immediately before ReplacementPolicy's
234 * findVictim() not to break cache resizing.
235 * Returns blocks in all ways belonging to the set of the address.
237 * @param addr The addr to a find possible locations for.
238 * @return The possible locations.
240 const std::vector<CacheBlk*> getPossibleLocations(Addr addr) const
242 return sets[extractSet(addr)].blks;
246 * Insert the new block into the cache and update replacement data.
248 * @param pkt Packet holding the address to update
249 * @param blk The block to update.
251 void insertBlock(const PacketPtr pkt, CacheBlk *blk) override
254 BaseTags::insertBlock(pkt, blk);
256 // Increment tag counter
259 // Update replacement policy
260 replacementPolicy->reset(blk->replacementData);
264 * Limit the allocation for the cache ways.
265 * @param ways The maximum number of ways available for replacement.
267 virtual void setWayAllocationMax(int ways) override
269 fatal_if(ways < 1, "Allocation limit must be greater than zero");
274 * Get the way allocation mask limit.
275 * @return The maximum number of ways available for replacement.
277 virtual int getWayAllocationMax() const override
283 * Generate the tag from the given address.
284 * @param addr The address to get the tag from.
285 * @return The tag of the address.
287 Addr extractTag(Addr addr) const override
289 return (addr >> tagShift);
293 * Regenerate the block address from the tag and set.
295 * @param block The block.
296 * @return the block address.
298 Addr regenerateBlkAddr(const CacheBlk* blk) const override
300 return ((blk->tag << tagShift) | ((Addr)blk->set << setShift));
303 void forEachBlk(std::function<void(CacheBlk &)> visitor) override {
304 for (CacheBlk& blk : blks) {
309 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override {
310 for (CacheBlk& blk : blks) {
320 * Calculate the set index from the address.
322 * @param addr The address to get the set from.
323 * @return The set index of the address.
325 int extractSet(Addr addr) const
327 return ((addr >> setShift) & setMask);
331 #endif //__MEM_CACHE_TAGS_BASE_SET_ASSOC_HH__