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28 * Authors: Daniel Carvalho
33 * Definitions of a base set associative sector tag store.
36 #include "mem/cache/tags/sector_tags.hh"
42 #include "base/intmath.hh"
43 #include "base/logging.hh"
44 #include "base/types.hh"
45 #include "debug/CacheRepl.hh"
46 #include "mem/cache/base.hh"
47 #include "mem/cache/replacement_policies/base.hh"
49 SectorTags::SectorTags(const SectorTagsParams
*p
)
50 : BaseTags(p
), assoc(p
->assoc
), allocAssoc(p
->assoc
),
51 sequentialAccess(p
->sequential_access
),
52 replacementPolicy(p
->replacement_policy
),
53 numBlocksPerSector(p
->num_blocks_per_sector
),
54 numSectors(numBlocks
/ p
->num_blocks_per_sector
),
55 numSets(numSectors
/ p
->assoc
),
56 blks(numBlocks
), secBlks(numSectors
), sets(numSets
),
57 sectorShift(floorLog2(blkSize
)),
58 setShift(sectorShift
+ floorLog2(numBlocksPerSector
)),
59 tagShift(setShift
+ floorLog2(numSets
)),
60 sectorMask(numBlocksPerSector
- 1), setMask(numSets
- 1)
63 fatal_if(blkSize
< 4 || !isPowerOf2(blkSize
),
64 "Block size must be at least 4 and a power of 2");
65 fatal_if(!isPowerOf2(numSets
),
66 "# of sets must be non-zero and a power of 2");
67 fatal_if(!isPowerOf2(numBlocksPerSector
),
68 "# of blocks per sector must be non-zero and a power of 2");
69 fatal_if(assoc
<= 0, "associativity must be greater than zero");
73 SectorTags::init(BaseCache
* cache
)
78 // Initialize all sets
79 unsigned sec_blk_index
= 0; // index into sector blks array
80 unsigned blk_index
= 0; // index into blks array
81 for (unsigned i
= 0; i
< numSets
; ++i
) {
82 sets
[i
].resize(assoc
);
84 // Initialize all sectors in this set
85 for (unsigned j
= 0; j
< assoc
; ++j
) {
86 // Select block within the set to be linked
87 SectorBlk
*& sec_blk
= sets
[i
][j
];
89 // Locate next cache sector
90 sec_blk
= &secBlks
[sec_blk_index
];
92 // Associate a replacement data entry to the sector
93 sec_blk
->replacementData
= replacementPolicy
->instantiateEntry();
95 // Initialize all blocks in this sector
96 sec_blk
->blks
.resize(numBlocksPerSector
);
97 for (unsigned k
= 0; k
< numBlocksPerSector
; ++k
){
98 // Select block within the set to be linked
99 SectorSubBlk
*& blk
= sec_blk
->blks
[k
];
101 // Locate next cache block
102 blk
= &blks
[blk_index
];
104 // Associate a data chunk to the block
105 blk
->data
= &dataBlks
[blkSize
*blk_index
];
107 // Associate sector block to this block
108 blk
->setSectorBlock(sec_blk
);
110 // Associate the sector replacement data to this block
111 blk
->replacementData
= sec_blk
->replacementData
;
113 // Set its set, way and sector offset
116 blk
->setSectorOffset(k
);
118 // Update block index
122 // Update sector block index
129 SectorTags::invalidate(CacheBlk
*blk
)
131 BaseTags::invalidate(blk
);
133 // Get block's sector
134 SectorSubBlk
* sub_blk
= static_cast<SectorSubBlk
*>(blk
);
135 const SectorBlk
* sector_blk
= sub_blk
->getSectorBlock();
137 // When a block in a sector is invalidated, it does not make the tag
138 // invalid automatically, as there might be other blocks in the sector
139 // using it. The tag is invalidated only when there is a single block
141 if (!sector_blk
->isValid()) {
142 // Decrease the number of tags in use
145 // Invalidate replacement data, as we're invalidating the sector
146 replacementPolicy
->invalidate(sector_blk
->replacementData
);
151 SectorTags::accessBlock(Addr addr
, bool is_secure
, Cycles
&lat
)
153 CacheBlk
*blk
= findBlock(addr
, is_secure
);
155 // Access all tags in parallel, hence one in each way. The data side
156 // either accesses all blocks in parallel, or one block sequentially on
157 // a hit. Sequential access with a miss doesn't access data.
158 tagAccesses
+= allocAssoc
;
159 if (sequentialAccess
) {
160 if (blk
!= nullptr) {
164 dataAccesses
+= allocAssoc
*numBlocksPerSector
;
167 if (blk
!= nullptr) {
170 // Check if the block to be accessed is available. If not,
171 // apply the accessLatency on top of block->whenReady.
172 if (blk
->whenReady
> curTick() &&
173 cache
->ticksToCycles(blk
->whenReady
- curTick()) >
175 lat
= cache
->ticksToCycles(blk
->whenReady
- curTick()) +
179 // Update number of references to accessed block
182 // Get block's sector
183 SectorSubBlk
* sub_blk
= static_cast<SectorSubBlk
*>(blk
);
184 const SectorBlk
* sector_blk
= sub_blk
->getSectorBlock();
186 // Update replacement data of accessed block, which is shared with
187 // the whole sector it belongs to
188 replacementPolicy
->touch(sector_blk
->replacementData
);
197 const std::vector
<SectorBlk
*>
198 SectorTags::getPossibleLocations(Addr addr
) const
200 return sets
[extractSet(addr
)];
204 SectorTags::insertBlock(const Addr addr
, const bool is_secure
,
205 const int src_master_ID
, const uint32_t task_ID
,
208 // Do common block insertion functionality
209 BaseTags::insertBlock(addr
, is_secure
, src_master_ID
, task_ID
, blk
);
211 // Get block's sector
212 SectorSubBlk
* sub_blk
= static_cast<SectorSubBlk
*>(blk
);
213 const SectorBlk
* sector_blk
= sub_blk
->getSectorBlock();
215 // When a block is inserted, the tag is only a newly used tag if the
216 // sector was not previously present in the cache.
217 // This assumes BaseTags::insertBlock does not set the valid bit.
218 if (sector_blk
->isValid()) {
219 // An existing entry's replacement data is just updated
220 replacementPolicy
->touch(sector_blk
->replacementData
);
222 // Increment tag counter
225 // A new entry resets the replacement data
226 replacementPolicy
->reset(sector_blk
->replacementData
);
231 SectorTags::findBlock(Addr addr
, bool is_secure
) const
233 // Extract sector tag
234 const Addr tag
= extractTag(addr
);
236 // The address can only be mapped to a specific location of a sector
237 // due to sectors being composed of contiguous-address entries
238 const Addr offset
= extractSectorOffset(addr
);
240 // Find all possible sector locations for the given address
241 const std::vector
<SectorBlk
*> locations
= getPossibleLocations(addr
);
244 for (const auto& sector
: locations
) {
245 auto blk
= sector
->blks
[offset
];
246 if (blk
->getTag() == tag
&& blk
->isValid() &&
247 blk
->isSecure() == is_secure
) {
252 // Did not find block
257 SectorTags::findBlockBySetAndWay(int set
, int way
) const
259 return sets
[set
][way
];
263 SectorTags::findVictim(Addr addr
, const bool is_secure
,
264 std::vector
<CacheBlk
*>& evict_blks
) const
266 // Get all possible locations of this sector
267 const std::vector
<SectorBlk
*> sector_locations
=
268 getPossibleLocations(addr
);
270 // Check if the sector this address belongs to has been allocated
271 Addr tag
= extractTag(addr
);
272 SectorBlk
* victim_sector
= nullptr;
273 for (const auto& sector
: sector_locations
){
274 if ((tag
== sector
->getTag()) && sector
->isValid() &&
275 (is_secure
== sector
->isSecure())){
276 victim_sector
= sector
;
281 // If the sector is not present
282 if (victim_sector
== nullptr){
283 // Choose replacement victim from replacement candidates
284 victim_sector
= static_cast<SectorBlk
*>(replacementPolicy
->getVictim(
285 std::vector
<ReplaceableEntry
*>(
286 sector_locations
.begin(), sector_locations
.end())));
289 // Get the location of the victim block within the sector
290 SectorSubBlk
* victim
= victim_sector
->blks
[extractSectorOffset(addr
)];
292 // Get evicted blocks. Blocks are only evicted if the sectors mismatch and
293 // the currently existing sector is valid.
294 if ((tag
== victim_sector
->getTag()) &&
295 (is_secure
== victim_sector
->isSecure())){
296 // It would be a hit if victim was valid, and upgrades do not call
297 // findVictim, so it cannot happen
298 assert(!victim
->isValid());
300 // The whole sector must be evicted to make room for the new sector
301 for (const auto& blk
: victim_sector
->blks
){
302 evict_blks
.push_back(blk
);
306 DPRINTF(CacheRepl
, "set %x, way %x, sector offset %x: %s\n",
307 "selecting blk for replacement\n", victim
->set
, victim
->way
,
308 victim
->getSectorOffset());
314 SectorTags::extractTag(Addr addr
) const
316 return addr
>> tagShift
;
320 SectorTags::extractSet(Addr addr
) const
322 return (addr
>> setShift
) & setMask
;
326 SectorTags::extractSectorOffset(Addr addr
) const
328 return (addr
>> sectorShift
) & sectorMask
;
332 SectorTags::regenerateBlkAddr(const CacheBlk
* blk
) const
334 const SectorSubBlk
* blk_cast
= static_cast<const SectorSubBlk
*>(blk
);
335 return ((blk_cast
->getTag() << tagShift
) | ((Addr
)blk
->set
<< setShift
) |
336 ((Addr
)blk_cast
->getSectorOffset() << sectorShift
));
340 SectorTags::forEachBlk(std::function
<void(CacheBlk
&)> visitor
)
342 for (SectorSubBlk
& blk
: blks
) {
348 SectorTags::anyBlk(std::function
<bool(CacheBlk
&)> visitor
)
350 for (SectorSubBlk
& blk
: blks
) {
359 SectorTagsParams::create()
361 return new SectorTags(this);