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1/*
2 * Copyright (c) 2012-2013,2016,2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Erik Hallnor
41 * Nikos Nikoleris
42 */
43
44/**
45 * @file
46 * Declaration of a fully associative LRU tag store.
47 */
48
49#ifndef __MEM_CACHE_TAGS_FA_LRU_HH__
50#define __MEM_CACHE_TAGS_FA_LRU_HH__
51
52#include <cstdint>
53#include <functional>
54#include <string>
55#include <unordered_map>
56
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"
66
67// Uncomment to enable sanity checks for the FALRU cache and the
68// TrackedCaches class
69//#define FALRU_DEBUG
70
71// A bitmask of the caches we are keeping track of. Currently the
72// lowest bit is the smallest cache we are tracking, as it is
73// specified by the corresponding parameter. The rest of the bits are
74// for exponentially growing cache sizes.
75typedef uint32_t CachesMask;
76
77/**
78 * A fully associative cache block.
79 */
80class FALRUBlk : public CacheBlk
81{
82 public:
83 /** The previous block in LRU order. */
84 FALRUBlk *prev;
85 /** The next block in LRU order. */
86 FALRUBlk *next;
87
88 /** A bit mask of the caches that fit this block. */
89 CachesMask inCachesMask;
90};
91
92/**
93 * A fully associative LRU cache. Keeps statistics for accesses to a number of
94 * cache sizes at once.
95 */
96class FALRU : public BaseTags
97{
98 public:
99 /** Typedef the block type used in this class. */
100 typedef FALRUBlk BlkType;
101
102 protected:
103 /** The cache blocks. */
104 FALRUBlk *blks;
105
106 /** The MRU block. */
107 FALRUBlk *head;
108 /** The LRU block. */
109 FALRUBlk *tail;
110
111 /** Hash table type mapping addresses to cache block pointers. */
112 typedef std::unordered_map<Addr, FALRUBlk *, std::hash<Addr> > hash_t;
113 /** Iterator into the address hash table. */
114 typedef hash_t::const_iterator tagIterator;
115
116 /** The address hash table. */
117 hash_t tagHash;
118
119 /**
120 * Find the cache block for the given address.
121 * @param addr The address to find.
122 * @return The cache block of the address, if any.
123 */
124 FALRUBlk * hashLookup(Addr addr) const;
125
126 /**
127 * Move a cache block to the MRU position.
128 *
129 * @param blk The block to promote.
130 */
131 void moveToHead(FALRUBlk *blk);
132
133 /**
134 * Move a cache block to the LRU position.
135 *
136 * @param blk The block to demote.
137 */
138 void moveToTail(FALRUBlk *blk);
139
140 public:
141 typedef FALRUParams Params;
142
143 /**
144 * Construct and initialize this cache tagstore.
145 */
146 FALRU(const Params *p);
147 ~FALRU();
148
149 /**
150 * Register the stats for this object.
151 */
152 void regStats() override;
153
154 /**
155 * Invalidate a cache block.
156 * @param blk The block to invalidate.
157 */
158 void invalidate(CacheBlk *blk) override;
159
160 /**
161 * Access block and update replacement data. May not succeed, in which
162 * case nullptr pointer is returned. This has all the implications of a
163 * cache access and should only be used as such.
164 * Returns the access latency and inCachesMask flags as a side effect.
165 * @param addr The address to look for.
166 * @param is_secure True if the target memory space is secure.
167 * @param lat The latency of the access.
168 * @param in_cache_mask Mask indicating the caches in which the blk fits.
169 * @return Pointer to the cache block.
170 */
171 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat,
172 CachesMask *in_cache_mask);
173
174 /**
175 * Just a wrapper of above function to conform with the base interface.
176 */
177 CacheBlk* accessBlock(Addr addr, bool is_secure, Cycles &lat) override;
178
179 /**
180 * Find the block in the cache, do not update the replacement data.
181 * @param addr The address to look for.
182 * @param is_secure True if the target memory space is secure.
183 * @param asid The address space ID.
184 * @return Pointer to the cache block.
185 */
186 CacheBlk* findBlock(Addr addr, bool is_secure) const override;
187
188 /**
189 * Find a block given set and way.
190 *
191 * @param set The set of the block.
192 * @param way The way of the block.
193 * @return The block.
194 */
195 ReplaceableEntry* findBlockBySetAndWay(int set, int way) const override;
196
197 /**
198 * Find replacement victim based on address. The list of evicted blocks
199 * only contains the victim.
200 *
201 * @param addr Address to find a victim for.
202 * @param is_secure True if the target memory space is secure.
203 * @param evict_blks Cache blocks to be evicted.
204 * @return Cache block to be replaced.
205 */
206 CacheBlk* findVictim(Addr addr, const bool is_secure,
207 std::vector<CacheBlk*>& evict_blks) const override;
208
209 /**
210 * Insert the new block into the cache and update replacement data.
211 *
212 * @param pkt Packet holding the address to update
213 * @param blk The block to update.
214 */
215 void insertBlock(const PacketPtr pkt, CacheBlk *blk) override;
216
217 /**
218 * Generate the tag from the addres. For fully associative this is just the
219 * block address.
220 * @param addr The address to get the tag from.
221 * @return The tag.
222 */
223 Addr extractTag(Addr addr) const override
224 {
225 return blkAlign(addr);
226 }
227
228 /**
229 * Regenerate the block address from the tag.
230 *
231 * @param block The block.
232 * @return the block address.
233 */
234 Addr regenerateBlkAddr(const CacheBlk* blk) const override
235 {
236 return blk->tag;
237 }
238
239 void forEachBlk(std::function<void(CacheBlk &)> visitor) override {
240 for (int i = 0; i < numBlocks; i++) {
241 visitor(blks[i]);
242 }
243 }
244
245 bool anyBlk(std::function<bool(CacheBlk &)> visitor) override {
246 for (int i = 0; i < numBlocks; i++) {
247 if (visitor(blks[i])) {
248 return true;
249 }
250 }
251 return false;
252 }
253
254 private:
255 /**
256 * Mechanism that allows us to simultaneously collect miss
257 * statistics for multiple caches. Currently, we keep track of
258 * caches from a set minimum size of interest up to the actual
259 * cache size.
260 */
261 class CacheTracking
262 {
263 public:
264 CacheTracking(unsigned min_size, unsigned max_size,
265 unsigned block_size)
266 : blkSize(block_size),
267 minTrackedSize(min_size),
268 numTrackedCaches(max_size > min_size ?
269 floorLog2(max_size) - floorLog2(min_size) : 0),
270 inAllCachesMask(mask(numTrackedCaches)),
271 boundaries(new FALRUBlk *[numTrackedCaches])
272 {
273 fatal_if(numTrackedCaches > sizeof(CachesMask) * 8,
274 "Not enough bits (%s) in type CachesMask type to keep "
275 "track of %d caches\n", sizeof(CachesMask),
276 numTrackedCaches);
277 }
278
279 ~CacheTracking()
280 {
281 delete[] boundaries;
282 }
283
284 /**
285 * Initialiaze cache blocks and the tracking mechanism
286 *
287 * All blocks in the cache need to be initialized once.
288 *
289 * @param blk the MRU block
290 * @param blk the LRU block
291 */
292 void init(FALRUBlk *head, FALRUBlk *tail);
293
294 /**
295 * Update boundaries as a block will be moved to the MRU.
296 *
297 * For all caches that didn't fit the block before moving it,
298 * we move their boundaries one block closer to the MRU. We
299 * also update InCacheMasks as neccessary.
300 *
301 * @param blk the block that will be moved to the head
302 */
303 void moveBlockToHead(FALRUBlk *blk);
304
305 /**
306 * Update boundaries as a block will be moved to the LRU.
307 *
308 * For all caches that fitted the block before moving it, we
309 * move their boundaries one block closer to the LRU. We
310 * also update InCacheMasks as neccessary.
311 *
312 * @param blk the block that will be moved to the head
313 */
314 void moveBlockToTail(FALRUBlk *blk);
315
316 /**
317 * Notify of a block access.
318 *
319 * This should be called every time a block is accessed and it
320 * updates statistics. If the input block is nullptr then we
321 * treat the access as a miss. The block's InCacheMask
322 * determines the caches in which the block fits.
323 *
324 * @param blk the block to record the access for
325 */
326 void recordAccess(FALRUBlk *blk);
327
328 /**
329 * Check that the tracking mechanism is in consistent state.
330 *
331 * Iterate from the head (MRU) to the tail (LRU) of the list
332 * of blocks and assert the inCachesMask and the boundaries
333 * are in consistent state.
334 *
335 * @param head the MRU block of the actual cache
336 * @param head the LRU block of the actual cache
337 */
338 void check(FALRUBlk *head, FALRUBlk *tail);
339
340 /**
341 * Register the stats for this object.
342 */
343 void regStats(std::string name);
344
345 private:
346 /** The size of the cache block */
347 const unsigned blkSize;
348 /** The smallest cache we are tracking */
349 const unsigned minTrackedSize;
350 /** The number of different size caches being tracked. */
351 const int numTrackedCaches;
352 /** A mask for all cache being tracked. */
353 const CachesMask inAllCachesMask;
354 /** Array of pointers to blocks at the cache boundaries. */
355 FALRUBlk** boundaries;
356
357 protected:
358 /**
359 * @defgroup FALRUStats Fully Associative LRU specific statistics
360 * The FA lru stack lets us track multiple cache sizes at once. These
361 * statistics track the hits and misses for different cache sizes.
362 * @{
363 */
364
365 /** Hits in each cache */
366 Stats::Vector hits;
367 /** Misses in each cache */
368 Stats::Vector misses;
369 /** Total number of accesses */
370 Stats::Scalar accesses;
371
372 /**
373 * @}
374 */
375 };
376 CacheTracking cacheTracking;
377};
378
379#endif // __MEM_CACHE_TAGS_FA_LRU_HH__