cache.hh revision 12719
1/* 2 * Copyright (c) 2012-2018 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) 2002-2005 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 * Dave Greene 42 * Steve Reinhardt 43 * Ron Dreslinski 44 * Andreas Hansson 45 */ 46 47/** 48 * @file 49 * Describes a cache based on template policies. 50 */ 51 52#ifndef __MEM_CACHE_CACHE_HH__ 53#define __MEM_CACHE_CACHE_HH__ 54 55#include <unordered_set> 56 57#include "base/logging.hh" // fatal, panic, and warn 58#include "enums/Clusivity.hh" 59#include "mem/cache/base.hh" 60#include "mem/cache/blk.hh" 61#include "mem/cache/mshr.hh" 62#include "mem/cache/tags/base.hh" 63#include "params/Cache.hh" 64#include "sim/eventq.hh" 65 66//Forward decleration 67class BasePrefetcher; 68 69/** 70 * A template-policy based cache. The behavior of the cache can be altered by 71 * supplying different template policies. TagStore handles all tag and data 72 * storage @sa TagStore, \ref gem5MemorySystem "gem5 Memory System" 73 */ 74class Cache : public BaseCache 75{ 76 protected: 77 78 /** 79 * The CPU-side port extends the base cache slave port with access 80 * functions for functional, atomic and timing requests. 81 */ 82 class CpuSidePort : public CacheSlavePort 83 { 84 private: 85 86 // a pointer to our specific cache implementation 87 Cache *cache; 88 89 protected: 90 91 virtual bool recvTimingSnoopResp(PacketPtr pkt); 92 93 virtual bool tryTiming(PacketPtr pkt); 94 95 virtual bool recvTimingReq(PacketPtr pkt); 96 97 virtual Tick recvAtomic(PacketPtr pkt); 98 99 virtual void recvFunctional(PacketPtr pkt); 100 101 virtual AddrRangeList getAddrRanges() const; 102 103 public: 104 105 CpuSidePort(const std::string &_name, Cache *_cache, 106 const std::string &_label); 107 108 }; 109 110 /** 111 * Override the default behaviour of sendDeferredPacket to enable 112 * the memory-side cache port to also send requests based on the 113 * current MSHR status. This queue has a pointer to our specific 114 * cache implementation and is used by the MemSidePort. 115 */ 116 class CacheReqPacketQueue : public ReqPacketQueue 117 { 118 119 protected: 120 121 Cache &cache; 122 SnoopRespPacketQueue &snoopRespQueue; 123 124 public: 125 126 CacheReqPacketQueue(Cache &cache, MasterPort &port, 127 SnoopRespPacketQueue &snoop_resp_queue, 128 const std::string &label) : 129 ReqPacketQueue(cache, port, label), cache(cache), 130 snoopRespQueue(snoop_resp_queue) { } 131 132 /** 133 * Override the normal sendDeferredPacket and do not only 134 * consider the transmit list (used for responses), but also 135 * requests. 136 */ 137 virtual void sendDeferredPacket(); 138 139 /** 140 * Check if there is a conflicting snoop response about to be 141 * send out, and if so simply stall any requests, and schedule 142 * a send event at the same time as the next snoop response is 143 * being sent out. 144 */ 145 bool checkConflictingSnoop(Addr addr) 146 { 147 if (snoopRespQueue.hasAddr(addr)) { 148 DPRINTF(CachePort, "Waiting for snoop response to be " 149 "sent\n"); 150 Tick when = snoopRespQueue.deferredPacketReadyTime(); 151 schedSendEvent(when); 152 return true; 153 } 154 return false; 155 } 156 }; 157 158 /** 159 * The memory-side port extends the base cache master port with 160 * access functions for functional, atomic and timing snoops. 161 */ 162 class MemSidePort : public CacheMasterPort 163 { 164 private: 165 166 /** The cache-specific queue. */ 167 CacheReqPacketQueue _reqQueue; 168 169 SnoopRespPacketQueue _snoopRespQueue; 170 171 // a pointer to our specific cache implementation 172 Cache *cache; 173 174 protected: 175 176 virtual void recvTimingSnoopReq(PacketPtr pkt); 177 178 virtual bool recvTimingResp(PacketPtr pkt); 179 180 virtual Tick recvAtomicSnoop(PacketPtr pkt); 181 182 virtual void recvFunctionalSnoop(PacketPtr pkt); 183 184 public: 185 186 MemSidePort(const std::string &_name, Cache *_cache, 187 const std::string &_label); 188 }; 189 190 /** Tag and data Storage */ 191 BaseTags *tags; 192 193 /** Prefetcher */ 194 BasePrefetcher *prefetcher; 195 196 /** Temporary cache block for occasional transitory use */ 197 CacheBlk *tempBlock; 198 199 /** 200 * This cache should allocate a block on a line-sized write miss. 201 */ 202 const bool doFastWrites; 203 204 /** 205 * Turn line-sized writes into WriteInvalidate transactions. 206 */ 207 void promoteWholeLineWrites(PacketPtr pkt); 208 209 /** 210 * Notify the prefetcher on every access, not just misses. 211 */ 212 const bool prefetchOnAccess; 213 214 /** 215 * Clusivity with respect to the upstream cache, determining if we 216 * fill into both this cache and the cache above on a miss. Note 217 * that we currently do not support strict clusivity policies. 218 */ 219 const Enums::Clusivity clusivity; 220 221 /** 222 * Determine if clean lines should be written back or not. In 223 * cases where a downstream cache is mostly inclusive we likely 224 * want it to act as a victim cache also for lines that have not 225 * been modified. Hence, we cannot simply drop the line (or send a 226 * clean evict), but rather need to send the actual data. 227 */ 228 const bool writebackClean; 229 230 /** 231 * Upstream caches need this packet until true is returned, so 232 * hold it for deletion until a subsequent call 233 */ 234 std::unique_ptr<Packet> pendingDelete; 235 236 /** 237 * Writebacks from the tempBlock, resulting on the response path 238 * in atomic mode, must happen after the call to recvAtomic has 239 * finished (for the right ordering of the packets). We therefore 240 * need to hold on to the packets, and have a method and an event 241 * to send them. 242 */ 243 PacketPtr tempBlockWriteback; 244 245 /** 246 * Send the outstanding tempBlock writeback. To be called after 247 * recvAtomic finishes in cases where the block we filled is in 248 * fact the tempBlock, and now needs to be written back. 249 */ 250 void writebackTempBlockAtomic() { 251 assert(tempBlockWriteback != nullptr); 252 PacketList writebacks{tempBlockWriteback}; 253 doWritebacksAtomic(writebacks); 254 tempBlockWriteback = nullptr; 255 } 256 257 /** 258 * An event to writeback the tempBlock after recvAtomic 259 * finishes. To avoid other calls to recvAtomic getting in 260 * between, we create this event with a higher priority. 261 */ 262 EventFunctionWrapper writebackTempBlockAtomicEvent; 263 264 /** 265 * Store the outstanding requests that we are expecting snoop 266 * responses from so we can determine which snoop responses we 267 * generated and which ones were merely forwarded. 268 */ 269 std::unordered_set<RequestPtr> outstandingSnoop; 270 271 /** 272 * Does all the processing necessary to perform the provided request. 273 * @param pkt The memory request to perform. 274 * @param blk The cache block to be updated. 275 * @param lat The latency of the access. 276 * @param writebacks List for any writebacks that need to be performed. 277 * @return Boolean indicating whether the request was satisfied. 278 */ 279 bool access(PacketPtr pkt, CacheBlk *&blk, 280 Cycles &lat, PacketList &writebacks); 281 282 /** 283 *Handle doing the Compare and Swap function for SPARC. 284 */ 285 void cmpAndSwap(CacheBlk *blk, PacketPtr pkt); 286 287 /** 288 * Find a block frame for new block at address addr targeting the 289 * given security space, assuming that the block is not currently 290 * in the cache. Append writebacks if any to provided packet 291 * list. Return free block frame. May return nullptr if there are 292 * no replaceable blocks at the moment. 293 */ 294 CacheBlk *allocateBlock(Addr addr, bool is_secure, PacketList &writebacks); 295 296 /** 297 * Invalidate a cache block. 298 * 299 * @param blk Block to invalidate 300 */ 301 void invalidateBlock(CacheBlk *blk); 302 303 /** 304 * Maintain the clusivity of this cache by potentially 305 * invalidating a block. This method works in conjunction with 306 * satisfyRequest, but is separate to allow us to handle all MSHR 307 * targets before potentially dropping a block. 308 * 309 * @param from_cache Whether we have dealt with a packet from a cache 310 * @param blk The block that should potentially be dropped 311 */ 312 void maintainClusivity(bool from_cache, CacheBlk *blk); 313 314 /** 315 * Populates a cache block and handles all outstanding requests for the 316 * satisfied fill request. This version takes two memory requests. One 317 * contains the fill data, the other is an optional target to satisfy. 318 * @param pkt The memory request with the fill data. 319 * @param blk The cache block if it already exists. 320 * @param writebacks List for any writebacks that need to be performed. 321 * @param allocate Whether to allocate a block or use the temp block 322 * @return Pointer to the new cache block. 323 */ 324 CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk, 325 PacketList &writebacks, bool allocate); 326 327 /** 328 * Determine whether we should allocate on a fill or not. If this 329 * cache is mostly inclusive with regards to the upstream cache(s) 330 * we always allocate (for any non-forwarded and cacheable 331 * requests). In the case of a mostly exclusive cache, we allocate 332 * on fill if the packet did not come from a cache, thus if we: 333 * are dealing with a whole-line write (the latter behaves much 334 * like a writeback), the original target packet came from a 335 * non-caching source, or if we are performing a prefetch or LLSC. 336 * 337 * @param cmd Command of the incoming requesting packet 338 * @return Whether we should allocate on the fill 339 */ 340 inline bool allocOnFill(MemCmd cmd) const override 341 { 342 return clusivity == Enums::mostly_incl || 343 cmd == MemCmd::WriteLineReq || 344 cmd == MemCmd::ReadReq || 345 cmd == MemCmd::WriteReq || 346 cmd.isPrefetch() || 347 cmd.isLLSC(); 348 } 349 350 /** 351 * Performs the access specified by the request. 352 * @param pkt The request to perform. 353 */ 354 void recvTimingReq(PacketPtr pkt); 355 356 /** 357 * Insert writebacks into the write buffer 358 */ 359 void doWritebacks(PacketList& writebacks, Tick forward_time); 360 361 /** 362 * Send writebacks down the memory hierarchy in atomic mode 363 */ 364 void doWritebacksAtomic(PacketList& writebacks); 365 366 /** 367 * Handling the special case of uncacheable write responses to 368 * make recvTimingResp less cluttered. 369 */ 370 void handleUncacheableWriteResp(PacketPtr pkt); 371 372 /** 373 * Service non-deferred MSHR targets using the received response 374 * 375 * Iterates through the list of targets that can be serviced with 376 * the current response. Any writebacks that need to performed 377 * must be appended to the writebacks parameter. 378 * 379 * @param mshr The MSHR that corresponds to the reponse 380 * @param pkt The response packet 381 * @param blk The reference block 382 * @param writebacks List of writebacks that need to be performed 383 */ 384 void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt, CacheBlk *blk, 385 PacketList& writebacks); 386 387 /** 388 * Handles a response (cache line fill/write ack) from the bus. 389 * @param pkt The response packet 390 */ 391 void recvTimingResp(PacketPtr pkt); 392 393 /** 394 * Snoops bus transactions to maintain coherence. 395 * @param pkt The current bus transaction. 396 */ 397 void recvTimingSnoopReq(PacketPtr pkt); 398 399 /** 400 * Handle a snoop response. 401 * @param pkt Snoop response packet 402 */ 403 void recvTimingSnoopResp(PacketPtr pkt); 404 405 /** 406 * Performs the access specified by the request. 407 * @param pkt The request to perform. 408 * @return The number of ticks required for the access. 409 */ 410 Tick recvAtomic(PacketPtr pkt); 411 412 /** 413 * Snoop for the provided request in the cache and return the estimated 414 * time taken. 415 * @param pkt The memory request to snoop 416 * @return The number of ticks required for the snoop. 417 */ 418 Tick recvAtomicSnoop(PacketPtr pkt); 419 420 /** 421 * Performs the access specified by the request. 422 * @param pkt The request to perform. 423 * @param fromCpuSide from the CPU side port or the memory side port 424 */ 425 void functionalAccess(PacketPtr pkt, bool fromCpuSide); 426 427 /** 428 * Perform any necessary updates to the block and perform any data 429 * exchange between the packet and the block. The flags of the 430 * packet are also set accordingly. 431 * 432 * @param pkt Request packet from upstream that hit a block 433 * @param blk Cache block that the packet hit 434 * @param deferred_response Whether this hit is to block that 435 * originally missed 436 * @param pending_downgrade Whether the writable flag is to be removed 437 * 438 * @return True if the block is to be invalidated 439 */ 440 void satisfyRequest(PacketPtr pkt, CacheBlk *blk, 441 bool deferred_response = false, 442 bool pending_downgrade = false); 443 444 void doTimingSupplyResponse(PacketPtr req_pkt, const uint8_t *blk_data, 445 bool already_copied, bool pending_inval); 446 447 /** 448 * Perform an upward snoop if needed, and update the block state 449 * (possibly invalidating the block). Also create a response if required. 450 * 451 * @param pkt Snoop packet 452 * @param blk Cache block being snooped 453 * @param is_timing Timing or atomic for the response 454 * @param is_deferred Is this a deferred snoop or not? 455 * @param pending_inval Do we have a pending invalidation? 456 * 457 * @return The snoop delay incurred by the upwards snoop 458 */ 459 uint32_t handleSnoop(PacketPtr pkt, CacheBlk *blk, 460 bool is_timing, bool is_deferred, bool pending_inval); 461 462 /** 463 * Create a writeback request for the given block. 464 * @param blk The block to writeback. 465 * @return The writeback request for the block. 466 */ 467 PacketPtr writebackBlk(CacheBlk *blk); 468 469 /** 470 * Create a writeclean request for the given block. 471 * @param blk The block to write clean 472 * @param dest The destination of this clean operation 473 * @return The write clean packet for the block. 474 */ 475 PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id); 476 477 /** 478 * Create a CleanEvict request for the given block. 479 * @param blk The block to evict. 480 * @return The CleanEvict request for the block. 481 */ 482 PacketPtr cleanEvictBlk(CacheBlk *blk); 483 484 485 void memWriteback() override; 486 void memInvalidate() override; 487 bool isDirty() const override; 488 489 /** 490 * Cache block visitor that writes back dirty cache blocks using 491 * functional writes. 492 * 493 * \return Always returns true. 494 */ 495 bool writebackVisitor(CacheBlk &blk); 496 /** 497 * Cache block visitor that invalidates all blocks in the cache. 498 * 499 * @warn Dirty cache lines will not be written back to memory. 500 * 501 * \return Always returns true. 502 */ 503 bool invalidateVisitor(CacheBlk &blk); 504 505 /** 506 * Create an appropriate downstream bus request packet for the 507 * given parameters. 508 * @param cpu_pkt The miss that needs to be satisfied. 509 * @param blk The block currently in the cache corresponding to 510 * cpu_pkt (nullptr if none). 511 * @param needsWritable Indicates that the block must be writable 512 * even if the request in cpu_pkt doesn't indicate that. 513 * @return A new Packet containing the request, or nullptr if the 514 * current request in cpu_pkt should just be forwarded on. 515 */ 516 PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk, 517 bool needsWritable) const; 518 519 /** 520 * Return the next queue entry to service, either a pending miss 521 * from the MSHR queue, a buffered write from the write buffer, or 522 * something from the prefetcher. This function is responsible 523 * for prioritizing among those sources on the fly. 524 */ 525 QueueEntry* getNextQueueEntry(); 526 527 /** 528 * Send up a snoop request and find cached copies. If cached copies are 529 * found, set the BLOCK_CACHED flag in pkt. 530 */ 531 bool isCachedAbove(PacketPtr pkt, bool is_timing = true) const; 532 533 /** 534 * Return whether there are any outstanding misses. 535 */ 536 bool outstandingMisses() const 537 { 538 return !mshrQueue.isEmpty(); 539 } 540 541 CacheBlk *findBlock(Addr addr, bool is_secure) const { 542 return tags->findBlock(addr, is_secure); 543 } 544 545 bool inCache(Addr addr, bool is_secure) const override { 546 return (tags->findBlock(addr, is_secure) != 0); 547 } 548 549 bool inMissQueue(Addr addr, bool is_secure) const override { 550 return (mshrQueue.findMatch(addr, is_secure) != 0); 551 } 552 553 /** 554 * Find next request ready time from among possible sources. 555 */ 556 Tick nextQueueReadyTime() const; 557 558 public: 559 /** Instantiates a basic cache object. */ 560 Cache(const CacheParams *p); 561 562 /** Non-default destructor is needed to deallocate memory. */ 563 virtual ~Cache(); 564 565 void regStats() override; 566 567 /** 568 * Take an MSHR, turn it into a suitable downstream packet, and 569 * send it out. This construct allows a queue entry to choose a suitable 570 * approach based on its type. 571 * 572 * @param mshr The MSHR to turn into a packet and send 573 * @return True if the port is waiting for a retry 574 */ 575 bool sendMSHRQueuePacket(MSHR* mshr); 576 577 /** 578 * Similar to sendMSHR, but for a write-queue entry 579 * instead. Create the packet, and send it, and if successful also 580 * mark the entry in service. 581 * 582 * @param wq_entry The write-queue entry to turn into a packet and send 583 * @return True if the port is waiting for a retry 584 */ 585 bool sendWriteQueuePacket(WriteQueueEntry* wq_entry); 586 587 /** serialize the state of the caches 588 * We currently don't support checkpointing cache state, so this panics. 589 */ 590 void serialize(CheckpointOut &cp) const override; 591 void unserialize(CheckpointIn &cp) override; 592}; 593 594/** 595 * Wrap a method and present it as a cache block visitor. 596 * 597 * For example the forEachBlk method in the tag arrays expects a 598 * callable object/function as their parameter. This class wraps a 599 * method in an object and presents callable object that adheres to 600 * the cache block visitor protocol. 601 */ 602class CacheBlkVisitorWrapper : public CacheBlkVisitor 603{ 604 public: 605 typedef bool (Cache::*VisitorPtr)(CacheBlk &blk); 606 607 CacheBlkVisitorWrapper(Cache &_cache, VisitorPtr _visitor) 608 : cache(_cache), visitor(_visitor) {} 609 610 bool operator()(CacheBlk &blk) override { 611 return (cache.*visitor)(blk); 612 } 613 614 private: 615 Cache &cache; 616 VisitorPtr visitor; 617}; 618 619/** 620 * Cache block visitor that determines if there are dirty blocks in a 621 * cache. 622 * 623 * Use with the forEachBlk method in the tag array to determine if the 624 * array contains dirty blocks. 625 */ 626class CacheBlkIsDirtyVisitor : public CacheBlkVisitor 627{ 628 public: 629 CacheBlkIsDirtyVisitor() 630 : _isDirty(false) {} 631 632 bool operator()(CacheBlk &blk) override { 633 if (blk.isDirty()) { 634 _isDirty = true; 635 return false; 636 } else { 637 return true; 638 } 639 } 640 641 /** 642 * Does the array contain a dirty line? 643 * 644 * \return true if yes, false otherwise. 645 */ 646 bool isDirty() const { return _isDirty; }; 647 648 private: 649 bool _isDirty; 650}; 651 652#endif // __MEM_CACHE_CACHE_HH__ 653