95{
96 protected:
97 /**
98 * Indexes to enumerate the MSHR queues.
99 */
100 enum MSHRQueueIndex {
101 MSHRQueue_MSHRs,
102 MSHRQueue_WriteBuffer
103 };
104
105 public:
106 /**
107 * Reasons for caches to be blocked.
108 */
109 enum BlockedCause {
110 Blocked_NoMSHRs = MSHRQueue_MSHRs,
111 Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
112 Blocked_NoTargets,
113 NUM_BLOCKED_CAUSES
114 };
115
116 protected:
117
118 /**
119 * A cache master port is used for the memory-side port of the
120 * cache, and in addition to the basic timing port that only sends
121 * response packets through a transmit list, it also offers the
122 * ability to schedule and send request packets (requests &
123 * writebacks). The send event is scheduled through schedSendEvent,
124 * and the sendDeferredPacket of the timing port is modified to
125 * consider both the transmit list and the requests from the MSHR.
126 */
127 class CacheMasterPort : public QueuedMasterPort
128 {
129
130 public:
131
132 /**
133 * Schedule a send of a request packet (from the MSHR). Note
134 * that we could already have a retry outstanding.
135 */
136 void schedSendEvent(Tick time)
137 {
138 DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
139 reqQueue.schedSendEvent(time);
140 }
141
142 protected:
143
144 CacheMasterPort(const std::string &_name, BaseCache *_cache,
145 ReqPacketQueue &_reqQueue,
146 SnoopRespPacketQueue &_snoopRespQueue) :
147 QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
148 { }
149
150 /**
151 * Memory-side port always snoops.
152 *
153 * @return always true
154 */
155 virtual bool isSnooping() const { return true; }
156 };
157
158 /**
159 * Override the default behaviour of sendDeferredPacket to enable
160 * the memory-side cache port to also send requests based on the
161 * current MSHR status. This queue has a pointer to our specific
162 * cache implementation and is used by the MemSidePort.
163 */
164 class CacheReqPacketQueue : public ReqPacketQueue
165 {
166
167 protected:
168
169 BaseCache &cache;
170 SnoopRespPacketQueue &snoopRespQueue;
171
172 public:
173
174 CacheReqPacketQueue(BaseCache &cache, MasterPort &port,
175 SnoopRespPacketQueue &snoop_resp_queue,
176 const std::string &label) :
177 ReqPacketQueue(cache, port, label), cache(cache),
178 snoopRespQueue(snoop_resp_queue) { }
179
180 /**
181 * Override the normal sendDeferredPacket and do not only
182 * consider the transmit list (used for responses), but also
183 * requests.
184 */
185 virtual void sendDeferredPacket();
186
187 /**
188 * Check if there is a conflicting snoop response about to be
189 * send out, and if so simply stall any requests, and schedule
190 * a send event at the same time as the next snoop response is
191 * being sent out.
192 *
193 * @param pkt The packet to check for conflicts against.
194 */
195 bool checkConflictingSnoop(const PacketPtr pkt)
196 {
197 if (snoopRespQueue.checkConflict(pkt, cache.blkSize)) {
198 DPRINTF(CachePort, "Waiting for snoop response to be "
199 "sent\n");
200 Tick when = snoopRespQueue.deferredPacketReadyTime();
201 schedSendEvent(when);
202 return true;
203 }
204 return false;
205 }
206 };
207
208
209 /**
210 * The memory-side port extends the base cache master port with
211 * access functions for functional, atomic and timing snoops.
212 */
213 class MemSidePort : public CacheMasterPort
214 {
215 private:
216
217 /** The cache-specific queue. */
218 CacheReqPacketQueue _reqQueue;
219
220 SnoopRespPacketQueue _snoopRespQueue;
221
222 // a pointer to our specific cache implementation
223 BaseCache *cache;
224
225 protected:
226
227 virtual void recvTimingSnoopReq(PacketPtr pkt);
228
229 virtual bool recvTimingResp(PacketPtr pkt);
230
231 virtual Tick recvAtomicSnoop(PacketPtr pkt);
232
233 virtual void recvFunctionalSnoop(PacketPtr pkt);
234
235 public:
236
237 MemSidePort(const std::string &_name, BaseCache *_cache,
238 const std::string &_label);
239 };
240
241 /**
242 * A cache slave port is used for the CPU-side port of the cache,
243 * and it is basically a simple timing port that uses a transmit
244 * list for responses to the CPU (or connected master). In
245 * addition, it has the functionality to block the port for
246 * incoming requests. If blocked, the port will issue a retry once
247 * unblocked.
248 */
249 class CacheSlavePort : public QueuedSlavePort
250 {
251
252 public:
253
254 /** Do not accept any new requests. */
255 void setBlocked();
256
257 /** Return to normal operation and accept new requests. */
258 void clearBlocked();
259
260 bool isBlocked() const { return blocked; }
261
262 protected:
263
264 CacheSlavePort(const std::string &_name, BaseCache *_cache,
265 const std::string &_label);
266
267 /** A normal packet queue used to store responses. */
268 RespPacketQueue queue;
269
270 bool blocked;
271
272 bool mustSendRetry;
273
274 private:
275
276 void processSendRetry();
277
278 EventFunctionWrapper sendRetryEvent;
279
280 };
281
282 /**
283 * The CPU-side port extends the base cache slave port with access
284 * functions for functional, atomic and timing requests.
285 */
286 class CpuSidePort : public CacheSlavePort
287 {
288 private:
289
290 // a pointer to our specific cache implementation
291 BaseCache *cache;
292
293 protected:
294 virtual bool recvTimingSnoopResp(PacketPtr pkt) override;
295
296 virtual bool tryTiming(PacketPtr pkt) override;
297
298 virtual bool recvTimingReq(PacketPtr pkt) override;
299
300 virtual Tick recvAtomic(PacketPtr pkt) override;
301
302 virtual void recvFunctional(PacketPtr pkt) override;
303
304 virtual AddrRangeList getAddrRanges() const override;
305
306 public:
307
308 CpuSidePort(const std::string &_name, BaseCache *_cache,
309 const std::string &_label);
310
311 };
312
313 CpuSidePort cpuSidePort;
314 MemSidePort memSidePort;
315
316 protected:
317
318 /** Miss status registers */
319 MSHRQueue mshrQueue;
320
321 /** Write/writeback buffer */
322 WriteQueue writeBuffer;
323
324 /** Tag and data Storage */
325 BaseTags *tags;
326
327 /** Prefetcher */
328 BasePrefetcher *prefetcher;
329
330 /** To probe when a cache hit occurs */
331 ProbePointArg<PacketPtr> *ppHit;
332
333 /** To probe when a cache miss occurs */
334 ProbePointArg<PacketPtr> *ppMiss;
335
336 /** To probe when a cache fill occurs */
337 ProbePointArg<PacketPtr> *ppFill;
338
339 /**
340 * The writeAllocator drive optimizations for streaming writes.
341 * It first determines whether a WriteReq MSHR should be delayed,
342 * thus ensuring that we wait longer in cases when we are write
343 * coalescing and allowing all the bytes of the line to be written
344 * before the MSHR packet is sent downstream. This works in unison
345 * with the tracking in the MSHR to check if the entire line is
346 * written. The write mode also affects the behaviour on filling
347 * any whole-line writes. Normally the cache allocates the line
348 * when receiving the InvalidateResp, but after seeing enough
349 * consecutive lines we switch to using the tempBlock, and thus
350 * end up not allocating the line, and instead turning the
351 * whole-line write into a writeback straight away.
352 */
353 WriteAllocator * const writeAllocator;
354
355 /**
356 * Temporary cache block for occasional transitory use. We use
357 * the tempBlock to fill when allocation fails (e.g., when there
358 * is an outstanding request that accesses the victim block) or
359 * when we want to avoid allocation (e.g., exclusive caches)
360 */
361 TempCacheBlk *tempBlock;
362
363 /**
364 * Upstream caches need this packet until true is returned, so
365 * hold it for deletion until a subsequent call
366 */
367 std::unique_ptr<Packet> pendingDelete;
368
369 /**
370 * Mark a request as in service (sent downstream in the memory
371 * system), effectively making this MSHR the ordering point.
372 */
373 void markInService(MSHR *mshr, bool pending_modified_resp)
374 {
375 bool wasFull = mshrQueue.isFull();
376 mshrQueue.markInService(mshr, pending_modified_resp);
377
378 if (wasFull && !mshrQueue.isFull()) {
379 clearBlocked(Blocked_NoMSHRs);
380 }
381 }
382
383 void markInService(WriteQueueEntry *entry)
384 {
385 bool wasFull = writeBuffer.isFull();
386 writeBuffer.markInService(entry);
387
388 if (wasFull && !writeBuffer.isFull()) {
389 clearBlocked(Blocked_NoWBBuffers);
390 }
391 }
392
393 /**
394 * Determine whether we should allocate on a fill or not. If this
395 * cache is mostly inclusive with regards to the upstream cache(s)
396 * we always allocate (for any non-forwarded and cacheable
397 * requests). In the case of a mostly exclusive cache, we allocate
398 * on fill if the packet did not come from a cache, thus if we:
399 * are dealing with a whole-line write (the latter behaves much
400 * like a writeback), the original target packet came from a
401 * non-caching source, or if we are performing a prefetch or LLSC.
402 *
403 * @param cmd Command of the incoming requesting packet
404 * @return Whether we should allocate on the fill
405 */
406 inline bool allocOnFill(MemCmd cmd) const
407 {
408 return clusivity == Enums::mostly_incl ||
409 cmd == MemCmd::WriteLineReq ||
410 cmd == MemCmd::ReadReq ||
411 cmd == MemCmd::WriteReq ||
412 cmd.isPrefetch() ||
413 cmd.isLLSC();
414 }
415
416 /**
417 * Regenerate block address using tags.
418 * Block address regeneration depends on whether we're using a temporary
419 * block or not.
420 *
421 * @param blk The block to regenerate address.
422 * @return The block's address.
423 */
424 Addr regenerateBlkAddr(CacheBlk* blk);
425
426 /**
427 * Calculate latency of accesses that only touch the tag array.
428 * @sa calculateAccessLatency
429 *
430 * @param delay The delay until the packet's metadata is present.
431 * @param lookup_lat Latency of the respective tag lookup.
432 * @return The number of ticks that pass due to a tag-only access.
433 */
434 Cycles calculateTagOnlyLatency(const uint32_t delay,
435 const Cycles lookup_lat) const;
436 /**
437 * Calculate access latency in ticks given a tag lookup latency, and
438 * whether access was a hit or miss.
439 *
440 * @param blk The cache block that was accessed.
441 * @param delay The delay until the packet's metadata is present.
442 * @param lookup_lat Latency of the respective tag lookup.
443 * @return The number of ticks that pass due to a block access.
444 */
445 Cycles calculateAccessLatency(const CacheBlk* blk, const uint32_t delay,
446 const Cycles lookup_lat) const;
447
448 /**
449 * Does all the processing necessary to perform the provided request.
450 * @param pkt The memory request to perform.
451 * @param blk The cache block to be updated.
452 * @param lat The latency of the access.
453 * @param writebacks List for any writebacks that need to be performed.
454 * @return Boolean indicating whether the request was satisfied.
455 */
456 virtual bool access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
457 PacketList &writebacks);
458
459 /*
460 * Handle a timing request that hit in the cache
461 *
462 * @param ptk The request packet
463 * @param blk The referenced block
464 * @param request_time The tick at which the block lookup is compete
465 */
466 virtual void handleTimingReqHit(PacketPtr pkt, CacheBlk *blk,
467 Tick request_time);
468
469 /*
470 * Handle a timing request that missed in the cache
471 *
472 * Implementation specific handling for different cache
473 * implementations
474 *
475 * @param ptk The request packet
476 * @param blk The referenced block
477 * @param forward_time The tick at which we can process dependent requests
478 * @param request_time The tick at which the block lookup is compete
479 */
480 virtual void handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk,
481 Tick forward_time,
482 Tick request_time) = 0;
483
484 /*
485 * Handle a timing request that missed in the cache
486 *
487 * Common functionality across different cache implementations
488 *
489 * @param ptk The request packet
490 * @param blk The referenced block
491 * @param mshr Any existing mshr for the referenced cache block
492 * @param forward_time The tick at which we can process dependent requests
493 * @param request_time The tick at which the block lookup is compete
494 */
495 void handleTimingReqMiss(PacketPtr pkt, MSHR *mshr, CacheBlk *blk,
496 Tick forward_time, Tick request_time);
497
498 /**
499 * Performs the access specified by the request.
500 * @param pkt The request to perform.
501 */
502 virtual void recvTimingReq(PacketPtr pkt);
503
504 /**
505 * Handling the special case of uncacheable write responses to
506 * make recvTimingResp less cluttered.
507 */
508 void handleUncacheableWriteResp(PacketPtr pkt);
509
510 /**
511 * Service non-deferred MSHR targets using the received response
512 *
513 * Iterates through the list of targets that can be serviced with
514 * the current response.
515 *
516 * @param mshr The MSHR that corresponds to the reponse
517 * @param pkt The response packet
518 * @param blk The reference block
519 */
520 virtual void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt,
521 CacheBlk *blk) = 0;
522
523 /**
524 * Handles a response (cache line fill/write ack) from the bus.
525 * @param pkt The response packet
526 */
527 virtual void recvTimingResp(PacketPtr pkt);
528
529 /**
530 * Snoops bus transactions to maintain coherence.
531 * @param pkt The current bus transaction.
532 */
533 virtual void recvTimingSnoopReq(PacketPtr pkt) = 0;
534
535 /**
536 * Handle a snoop response.
537 * @param pkt Snoop response packet
538 */
539 virtual void recvTimingSnoopResp(PacketPtr pkt) = 0;
540
541 /**
542 * Handle a request in atomic mode that missed in this cache
543 *
544 * Creates a downstream request, sends it to the memory below and
545 * handles the response. As we are in atomic mode all operations
546 * are performed immediately.
547 *
548 * @param pkt The packet with the requests
549 * @param blk The referenced block
550 * @param writebacks A list with packets for any performed writebacks
551 * @return Cycles for handling the request
552 */
553 virtual Cycles handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
554 PacketList &writebacks) = 0;
555
556 /**
557 * Performs the access specified by the request.
558 * @param pkt The request to perform.
559 * @return The number of ticks required for the access.
560 */
561 virtual Tick recvAtomic(PacketPtr pkt);
562
563 /**
564 * Snoop for the provided request in the cache and return the estimated
565 * time taken.
566 * @param pkt The memory request to snoop
567 * @return The number of ticks required for the snoop.
568 */
569 virtual Tick recvAtomicSnoop(PacketPtr pkt) = 0;
570
571 /**
572 * Performs the access specified by the request.
573 *
574 * @param pkt The request to perform.
575 * @param fromCpuSide from the CPU side port or the memory side port
576 */
577 virtual void functionalAccess(PacketPtr pkt, bool from_cpu_side);
578
579 /**
580 * Handle doing the Compare and Swap function for SPARC.
581 */
582 void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
583
584 /**
585 * Return the next queue entry to service, either a pending miss
586 * from the MSHR queue, a buffered write from the write buffer, or
587 * something from the prefetcher. This function is responsible
588 * for prioritizing among those sources on the fly.
589 */
590 QueueEntry* getNextQueueEntry();
591
592 /**
593 * Insert writebacks into the write buffer
594 */
595 virtual void doWritebacks(PacketList& writebacks, Tick forward_time) = 0;
596
597 /**
598 * Send writebacks down the memory hierarchy in atomic mode
599 */
600 virtual void doWritebacksAtomic(PacketList& writebacks) = 0;
601
602 /**
603 * Create an appropriate downstream bus request packet.
604 *
605 * Creates a new packet with the request to be send to the memory
606 * below, or nullptr if the current request in cpu_pkt should just
607 * be forwarded on.
608 *
609 * @param cpu_pkt The miss packet that needs to be satisfied.
610 * @param blk The referenced block, can be nullptr.
611 * @param needs_writable Indicates that the block must be writable
612 * even if the request in cpu_pkt doesn't indicate that.
613 * @param is_whole_line_write True if there are writes for the
614 * whole line
615 * @return A packet send to the memory below
616 */
617 virtual PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
618 bool needs_writable,
619 bool is_whole_line_write) const = 0;
620
621 /**
622 * Determine if clean lines should be written back or not. In
623 * cases where a downstream cache is mostly inclusive we likely
624 * want it to act as a victim cache also for lines that have not
625 * been modified. Hence, we cannot simply drop the line (or send a
626 * clean evict), but rather need to send the actual data.
627 */
628 const bool writebackClean;
629
630 /**
631 * Writebacks from the tempBlock, resulting on the response path
632 * in atomic mode, must happen after the call to recvAtomic has
633 * finished (for the right ordering of the packets). We therefore
634 * need to hold on to the packets, and have a method and an event
635 * to send them.
636 */
637 PacketPtr tempBlockWriteback;
638
639 /**
640 * Send the outstanding tempBlock writeback. To be called after
641 * recvAtomic finishes in cases where the block we filled is in
642 * fact the tempBlock, and now needs to be written back.
643 */
644 void writebackTempBlockAtomic() {
645 assert(tempBlockWriteback != nullptr);
646 PacketList writebacks{tempBlockWriteback};
647 doWritebacksAtomic(writebacks);
648 tempBlockWriteback = nullptr;
649 }
650
651 /**
652 * An event to writeback the tempBlock after recvAtomic
653 * finishes. To avoid other calls to recvAtomic getting in
654 * between, we create this event with a higher priority.
655 */
656 EventFunctionWrapper writebackTempBlockAtomicEvent;
657
658 /**
659 * Perform any necessary updates to the block and perform any data
660 * exchange between the packet and the block. The flags of the
661 * packet are also set accordingly.
662 *
663 * @param pkt Request packet from upstream that hit a block
664 * @param blk Cache block that the packet hit
665 * @param deferred_response Whether this request originally missed
666 * @param pending_downgrade Whether the writable flag is to be removed
667 */
668 virtual void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
669 bool deferred_response = false,
670 bool pending_downgrade = false);
671
672 /**
673 * Maintain the clusivity of this cache by potentially
674 * invalidating a block. This method works in conjunction with
675 * satisfyRequest, but is separate to allow us to handle all MSHR
676 * targets before potentially dropping a block.
677 *
678 * @param from_cache Whether we have dealt with a packet from a cache
679 * @param blk The block that should potentially be dropped
680 */
681 void maintainClusivity(bool from_cache, CacheBlk *blk);
682
683 /**
684 * Handle a fill operation caused by a received packet.
685 *
686 * Populates a cache block and handles all outstanding requests for the
687 * satisfied fill request. This version takes two memory requests. One
688 * contains the fill data, the other is an optional target to satisfy.
689 * Note that the reason we return a list of writebacks rather than
690 * inserting them directly in the write buffer is that this function
691 * is called by both atomic and timing-mode accesses, and in atomic
692 * mode we don't mess with the write buffer (we just perform the
693 * writebacks atomically once the original request is complete).
694 *
695 * @param pkt The memory request with the fill data.
696 * @param blk The cache block if it already exists.
697 * @param writebacks List for any writebacks that need to be performed.
698 * @param allocate Whether to allocate a block or use the temp block
699 * @return Pointer to the new cache block.
700 */
701 CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
702 PacketList &writebacks, bool allocate);
703
704 /**
705 * Allocate a new block and perform any necessary writebacks
706 *
707 * Find a victim block and if necessary prepare writebacks for any
708 * existing data. May return nullptr if there are no replaceable
709 * blocks. If a replaceable block is found, it inserts the new block in
710 * its place. The new block, however, is not set as valid yet.
711 *
712 * @param pkt Packet holding the address to update
713 * @param writebacks A list of writeback packets for the evicted blocks
714 * @return the allocated block
715 */
716 CacheBlk *allocateBlock(const PacketPtr pkt, PacketList &writebacks);
717 /**
718 * Evict a cache block.
719 *
720 * Performs a writeback if necesssary and invalidates the block
721 *
722 * @param blk Block to invalidate
723 * @return A packet with the writeback, can be nullptr
724 */
725 M5_NODISCARD virtual PacketPtr evictBlock(CacheBlk *blk) = 0;
726
727 /**
728 * Evict a cache block.
729 *
730 * Performs a writeback if necesssary and invalidates the block
731 *
732 * @param blk Block to invalidate
733 * @param writebacks Return a list of packets with writebacks
734 */
735 void evictBlock(CacheBlk *blk, PacketList &writebacks);
736
737 /**
738 * Invalidate a cache block.
739 *
740 * @param blk Block to invalidate
741 */
742 void invalidateBlock(CacheBlk *blk);
743
744 /**
745 * Create a writeback request for the given block.
746 *
747 * @param blk The block to writeback.
748 * @return The writeback request for the block.
749 */
750 PacketPtr writebackBlk(CacheBlk *blk);
751
752 /**
753 * Create a writeclean request for the given block.
754 *
755 * Creates a request that writes the block to the cache below
756 * without evicting the block from the current cache.
757 *
758 * @param blk The block to write clean.
759 * @param dest The destination of the write clean operation.
760 * @param id Use the given packet id for the write clean operation.
761 * @return The generated write clean packet.
762 */
763 PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id);
764
765 /**
766 * Write back dirty blocks in the cache using functional accesses.
767 */
768 virtual void memWriteback() override;
769
770 /**
771 * Invalidates all blocks in the cache.
772 *
773 * @warn Dirty cache lines will not be written back to
774 * memory. Make sure to call functionalWriteback() first if you
775 * want the to write them to memory.
776 */
777 virtual void memInvalidate() override;
778
779 /**
780 * Determine if there are any dirty blocks in the cache.
781 *
782 * @return true if at least one block is dirty, false otherwise.
783 */
784 bool isDirty() const;
785
786 /**
787 * Determine if an address is in the ranges covered by this
788 * cache. This is useful to filter snoops.
789 *
790 * @param addr Address to check against
791 *
792 * @return If the address in question is in range
793 */
794 bool inRange(Addr addr) const;
795
796 /**
797 * Find next request ready time from among possible sources.
798 */
799 Tick nextQueueReadyTime() const;
800
801 /** Block size of this cache */
802 const unsigned blkSize;
803
804 /**
805 * The latency of tag lookup of a cache. It occurs when there is
806 * an access to the cache.
807 */
808 const Cycles lookupLatency;
809
810 /**
811 * The latency of data access of a cache. It occurs when there is
812 * an access to the cache.
813 */
814 const Cycles dataLatency;
815
816 /**
817 * This is the forward latency of the cache. It occurs when there
818 * is a cache miss and a request is forwarded downstream, in
819 * particular an outbound miss.
820 */
821 const Cycles forwardLatency;
822
823 /** The latency to fill a cache block */
824 const Cycles fillLatency;
825
826 /**
827 * The latency of sending reponse to its upper level cache/core on
828 * a linefill. The responseLatency parameter captures this
829 * latency.
830 */
831 const Cycles responseLatency;
832
833 /**
834 * Whether tags and data are accessed sequentially.
835 */
836 const bool sequentialAccess;
837
838 /** The number of targets for each MSHR. */
839 const int numTarget;
840
841 /** Do we forward snoops from mem side port through to cpu side port? */
842 bool forwardSnoops;
843
844 /**
845 * Clusivity with respect to the upstream cache, determining if we
846 * fill into both this cache and the cache above on a miss. Note
847 * that we currently do not support strict clusivity policies.
848 */
849 const Enums::Clusivity clusivity;
850
851 /**
852 * Is this cache read only, for example the instruction cache, or
853 * table-walker cache. A cache that is read only should never see
854 * any writes, and should never get any dirty data (and hence
855 * never have to do any writebacks).
856 */
857 const bool isReadOnly;
858
859 /**
860 * Bit vector of the blocking reasons for the access path.
861 * @sa #BlockedCause
862 */
863 uint8_t blocked;
864
865 /** Increasing order number assigned to each incoming request. */
866 uint64_t order;
867
868 /** Stores time the cache blocked for statistics. */
869 Cycles blockedCycle;
870
871 /** Pointer to the MSHR that has no targets. */
872 MSHR *noTargetMSHR;
873
874 /** The number of misses to trigger an exit event. */
875 Counter missCount;
876
877 /**
878 * The address range to which the cache responds on the CPU side.
879 * Normally this is all possible memory addresses. */
880 const AddrRangeList addrRanges;
881
882 public:
883 /** System we are currently operating in. */
884 System *system;
885
886 // Statistics
887 /**
888 * @addtogroup CacheStatistics
889 * @{
890 */
891
892 /** Number of hits per thread for each type of command.
893 @sa Packet::Command */
894 Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
895 /** Number of hits for demand accesses. */
896 Stats::Formula demandHits;
897 /** Number of hit for all accesses. */
898 Stats::Formula overallHits;
899
900 /** Number of misses per thread for each type of command.
901 @sa Packet::Command */
902 Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
903 /** Number of misses for demand accesses. */
904 Stats::Formula demandMisses;
905 /** Number of misses for all accesses. */
906 Stats::Formula overallMisses;
907
908 /**
909 * Total number of cycles per thread/command spent waiting for a miss.
910 * Used to calculate the average miss latency.
911 */
912 Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
913 /** Total number of cycles spent waiting for demand misses. */
914 Stats::Formula demandMissLatency;
915 /** Total number of cycles spent waiting for all misses. */
916 Stats::Formula overallMissLatency;
917
918 /** The number of accesses per command and thread. */
919 Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
920 /** The number of demand accesses. */
921 Stats::Formula demandAccesses;
922 /** The number of overall accesses. */
923 Stats::Formula overallAccesses;
924
925 /** The miss rate per command and thread. */
926 Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
927 /** The miss rate of all demand accesses. */
928 Stats::Formula demandMissRate;
929 /** The miss rate for all accesses. */
930 Stats::Formula overallMissRate;
931
932 /** The average miss latency per command and thread. */
933 Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
934 /** The average miss latency for demand misses. */
935 Stats::Formula demandAvgMissLatency;
936 /** The average miss latency for all misses. */
937 Stats::Formula overallAvgMissLatency;
938
939 /** The total number of cycles blocked for each blocked cause. */
940 Stats::Vector blocked_cycles;
941 /** The number of times this cache blocked for each blocked cause. */
942 Stats::Vector blocked_causes;
943
944 /** The average number of cycles blocked for each blocked cause. */
945 Stats::Formula avg_blocked;
946
947 /** The number of times a HW-prefetched block is evicted w/o reference. */
948 Stats::Scalar unusedPrefetches;
949
950 /** Number of blocks written back per thread. */
951 Stats::Vector writebacks;
952
953 /** Number of misses that hit in the MSHRs per command and thread. */
954 Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
955 /** Demand misses that hit in the MSHRs. */
956 Stats::Formula demandMshrHits;
957 /** Total number of misses that hit in the MSHRs. */
958 Stats::Formula overallMshrHits;
959
960 /** Number of misses that miss in the MSHRs, per command and thread. */
961 Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
962 /** Demand misses that miss in the MSHRs. */
963 Stats::Formula demandMshrMisses;
964 /** Total number of misses that miss in the MSHRs. */
965 Stats::Formula overallMshrMisses;
966
967 /** Number of misses that miss in the MSHRs, per command and thread. */
968 Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
969 /** Total number of misses that miss in the MSHRs. */
970 Stats::Formula overallMshrUncacheable;
971
972 /** Total cycle latency of each MSHR miss, per command and thread. */
973 Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
974 /** Total cycle latency of demand MSHR misses. */
975 Stats::Formula demandMshrMissLatency;
976 /** Total cycle latency of overall MSHR misses. */
977 Stats::Formula overallMshrMissLatency;
978
979 /** Total cycle latency of each MSHR miss, per command and thread. */
980 Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
981 /** Total cycle latency of overall MSHR misses. */
982 Stats::Formula overallMshrUncacheableLatency;
983
984#if 0
985 /** The total number of MSHR accesses per command and thread. */
986 Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
987 /** The total number of demand MSHR accesses. */
988 Stats::Formula demandMshrAccesses;
989 /** The total number of MSHR accesses. */
990 Stats::Formula overallMshrAccesses;
991#endif
992
993 /** The miss rate in the MSHRs pre command and thread. */
994 Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
995 /** The demand miss rate in the MSHRs. */
996 Stats::Formula demandMshrMissRate;
997 /** The overall miss rate in the MSHRs. */
998 Stats::Formula overallMshrMissRate;
999
1000 /** The average latency of an MSHR miss, per command and thread. */
1001 Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
1002 /** The average latency of a demand MSHR miss. */
1003 Stats::Formula demandAvgMshrMissLatency;
1004 /** The average overall latency of an MSHR miss. */
1005 Stats::Formula overallAvgMshrMissLatency;
1006
1007 /** The average latency of an MSHR miss, per command and thread. */
1008 Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
1009 /** The average overall latency of an MSHR miss. */
1010 Stats::Formula overallAvgMshrUncacheableLatency;
1011
1012 /** Number of replacements of valid blocks. */
1013 Stats::Scalar replacements;
1014
1015 /**
1016 * @}
1017 */
1018
1019 /**
1020 * Register stats for this object.
1021 */
1022 void regStats() override;
1023
1024 /** Registers probes. */
1025 void regProbePoints() override;
1026
1027 public:
1028 BaseCache(const BaseCacheParams *p, unsigned blk_size);
1029 ~BaseCache();
1030
1031 void init() override;
1032
1033 Port &getPort(const std::string &if_name,
1034 PortID idx=InvalidPortID) override;
1035
1036 /**
1037 * Query block size of a cache.
1038 * @return The block size
1039 */
1040 unsigned
1041 getBlockSize() const
1042 {
1043 return blkSize;
1044 }
1045
1046 const AddrRangeList &getAddrRanges() const { return addrRanges; }
1047
1048 MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
1049 {
1050 MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
1051 pkt, time, order++,
1052 allocOnFill(pkt->cmd));
1053
1054 if (mshrQueue.isFull()) {
1055 setBlocked((BlockedCause)MSHRQueue_MSHRs);
1056 }
1057
1058 if (sched_send) {
1059 // schedule the send
1060 schedMemSideSendEvent(time);
1061 }
1062
1063 return mshr;
1064 }
1065
1066 void allocateWriteBuffer(PacketPtr pkt, Tick time)
1067 {
1068 // should only see writes or clean evicts here
1069 assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);
1070
1071 Addr blk_addr = pkt->getBlockAddr(blkSize);
1072
1073 WriteQueueEntry *wq_entry =
1074 writeBuffer.findMatch(blk_addr, pkt->isSecure());
1075 if (wq_entry && !wq_entry->inService) {
1076 DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
1077 }
1078
1079 writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);
1080
1081 if (writeBuffer.isFull()) {
1082 setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
1083 }
1084
1085 // schedule the send
1086 schedMemSideSendEvent(time);
1087 }
1088
1089 /**
1090 * Returns true if the cache is blocked for accesses.
1091 */
1092 bool isBlocked() const
1093 {
1094 return blocked != 0;
1095 }
1096
1097 /**
1098 * Marks the access path of the cache as blocked for the given cause. This
1099 * also sets the blocked flag in the slave interface.
1100 * @param cause The reason for the cache blocking.
1101 */
1102 void setBlocked(BlockedCause cause)
1103 {
1104 uint8_t flag = 1 << cause;
1105 if (blocked == 0) {
1106 blocked_causes[cause]++;
1107 blockedCycle = curCycle();
1108 cpuSidePort.setBlocked();
1109 }
1110 blocked |= flag;
1111 DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
1112 }
1113
1114 /**
1115 * Marks the cache as unblocked for the given cause. This also clears the
1116 * blocked flags in the appropriate interfaces.
1117 * @param cause The newly unblocked cause.
1118 * @warning Calling this function can cause a blocked request on the bus to
1119 * access the cache. The cache must be in a state to handle that request.
1120 */
1121 void clearBlocked(BlockedCause cause)
1122 {
1123 uint8_t flag = 1 << cause;
1124 blocked &= ~flag;
1125 DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
1126 if (blocked == 0) {
1127 blocked_cycles[cause] += curCycle() - blockedCycle;
1128 cpuSidePort.clearBlocked();
1129 }
1130 }
1131
1132 /**
1133 * Schedule a send event for the memory-side port. If already
1134 * scheduled, this may reschedule the event at an earlier
1135 * time. When the specified time is reached, the port is free to
1136 * send either a response, a request, or a prefetch request.
1137 *
1138 * @param time The time when to attempt sending a packet.
1139 */
1140 void schedMemSideSendEvent(Tick time)
1141 {
1142 memSidePort.schedSendEvent(time);
1143 }
1144
1145 bool inCache(Addr addr, bool is_secure) const {
1146 return tags->findBlock(addr, is_secure);
1147 }
1148
1149 bool hasBeenPrefetched(Addr addr, bool is_secure) const {
1150 CacheBlk *block = tags->findBlock(addr, is_secure);
1151 if (block) {
1152 return block->wasPrefetched();
1153 } else {
1154 return false;
1155 }
1156 }
1157
1158 bool inMissQueue(Addr addr, bool is_secure) const {
1159 return mshrQueue.findMatch(addr, is_secure);
1160 }
1161
1162 void incMissCount(PacketPtr pkt)
1163 {
1164 assert(pkt->req->masterId() < system->maxMasters());
1165 misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
1166 pkt->req->incAccessDepth();
1167 if (missCount) {
1168 --missCount;
1169 if (missCount == 0)
1170 exitSimLoop("A cache reached the maximum miss count");
1171 }
1172 }
1173 void incHitCount(PacketPtr pkt)
1174 {
1175 assert(pkt->req->masterId() < system->maxMasters());
1176 hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
1177
1178 }
1179
1180 /**
1181 * Checks if the cache is coalescing writes
1182 *
1183 * @return True if the cache is coalescing writes
1184 */
1185 bool coalesce() const;
1186
1187
1188 /**
1189 * Cache block visitor that writes back dirty cache blocks using
1190 * functional writes.
1191 */
1192 void writebackVisitor(CacheBlk &blk);
1193
1194 /**
1195 * Cache block visitor that invalidates all blocks in the cache.
1196 *
1197 * @warn Dirty cache lines will not be written back to memory.
1198 */
1199 void invalidateVisitor(CacheBlk &blk);
1200
1201 /**
1202 * Take an MSHR, turn it into a suitable downstream packet, and
1203 * send it out. This construct allows a queue entry to choose a suitable
1204 * approach based on its type.
1205 *
1206 * @param mshr The MSHR to turn into a packet and send
1207 * @return True if the port is waiting for a retry
1208 */
1209 virtual bool sendMSHRQueuePacket(MSHR* mshr);
1210
1211 /**
1212 * Similar to sendMSHR, but for a write-queue entry
1213 * instead. Create the packet, and send it, and if successful also
1214 * mark the entry in service.
1215 *
1216 * @param wq_entry The write-queue entry to turn into a packet and send
1217 * @return True if the port is waiting for a retry
1218 */
1219 bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
1220
1221 /**
1222 * Serialize the state of the caches
1223 *
1224 * We currently don't support checkpointing cache state, so this panics.
1225 */
1226 void serialize(CheckpointOut &cp) const override;
1227 void unserialize(CheckpointIn &cp) override;
1228};
1229
1230/**
1231 * The write allocator inspects write packets and detects streaming
1232 * patterns. The write allocator supports a single stream where writes
1233 * are expected to access consecutive locations and keeps track of
1234 * size of the area covered by the concecutive writes in byteCount.
1235 *
1236 * 1) When byteCount has surpassed the coallesceLimit the mode
1237 * switches from ALLOCATE to COALESCE where writes should be delayed
1238 * until the whole block is written at which point a single packet
1239 * (whole line write) can service them.
1240 *
1241 * 2) When byteCount has also exceeded the noAllocateLimit (whole
1242 * line) we switch to NO_ALLOCATE when writes should not allocate in
1243 * the cache but rather send a whole line write to the memory below.
1244 */
1245class WriteAllocator : public SimObject {
1246 public:
1247 WriteAllocator(const WriteAllocatorParams *p) :
1248 SimObject(p),
1249 coalesceLimit(p->coalesce_limit * p->block_size),
1250 noAllocateLimit(p->no_allocate_limit * p->block_size),
1251 delayThreshold(p->delay_threshold)
1252 {
1253 reset();
1254 }
1255
1256 /**
1257 * Should writes be coalesced? This is true if the mode is set to
1258 * NO_ALLOCATE.
1259 *
1260 * @return return true if the cache should coalesce writes.
1261 */
1262 bool coalesce() const {
1263 return mode != WriteMode::ALLOCATE;
1264 }
1265
1266 /**
1267 * Should writes allocate?
1268 *
1269 * @return return true if the cache should not allocate for writes.
1270 */
1271 bool allocate() const {
1272 return mode != WriteMode::NO_ALLOCATE;
1273 }
1274
1275 /**
1276 * Reset the write allocator state, meaning that it allocates for
1277 * writes and has not recorded any information about qualifying
1278 * writes that might trigger a switch to coalescing and later no
1279 * allocation.
1280 */
1281 void reset() {
1282 mode = WriteMode::ALLOCATE;
1283 byteCount = 0;
1284 nextAddr = 0;
1285 }
1286
1287 /**
1288 * Access whether we need to delay the current write.
1289 *
1290 * @param blk_addr The block address the packet writes to
1291 * @return true if the current packet should be delayed
1292 */
1293 bool delay(Addr blk_addr) {
1294 if (delayCtr[blk_addr] > 0) {
1295 --delayCtr[blk_addr];
1296 return true;
1297 } else {
1298 return false;
1299 }
1300 }
1301
1302 /**
1303 * Clear delay counter for the input block
1304 *
1305 * @param blk_addr The accessed cache block
1306 */
1307 void resetDelay(Addr blk_addr) {
1308 delayCtr.erase(blk_addr);
1309 }
1310
1311 /**
1312 * Update the write mode based on the current write
1313 * packet. This method compares the packet's address with any
1314 * current stream, and updates the tracking and the mode
1315 * accordingly.
1316 *
1317 * @param write_addr Start address of the write request
1318 * @param write_size Size of the write request
1319 * @param blk_addr The block address that this packet writes to
1320 */
1321 void updateMode(Addr write_addr, unsigned write_size, Addr blk_addr);
1322
1323 private:
1324 /**
1325 * The current mode for write coalescing and allocation, either
1326 * normal operation (ALLOCATE), write coalescing (COALESCE), or
1327 * write coalescing without allocation (NO_ALLOCATE).
1328 */
1329 enum class WriteMode : char {
1330 ALLOCATE,
1331 COALESCE,
1332 NO_ALLOCATE,
1333 };
1334 WriteMode mode;
1335
1336 /** Address to match writes against to detect streams. */
1337 Addr nextAddr;
1338
1339 /**
1340 * Bytes written contiguously. Saturating once we no longer
1341 * allocate.
1342 */
1343 uint32_t byteCount;
1344
1345 /**
1346 * Limits for when to switch between the different write modes.
1347 */
1348 const uint32_t coalesceLimit;
1349 const uint32_t noAllocateLimit;
1350 /**
1351 * The number of times the allocator will delay an WriteReq MSHR.
1352 */
1353 const uint32_t delayThreshold;
1354
1355 /**
1356 * Keep track of the number of times the allocator has delayed an
1357 * WriteReq MSHR.
1358 */
1359 std::unordered_map<Addr, Counter> delayCtr;
1360};
1361
1362#endif //__MEM_CACHE_BASE_HH__
| 95{
96 protected:
97 /**
98 * Indexes to enumerate the MSHR queues.
99 */
100 enum MSHRQueueIndex {
101 MSHRQueue_MSHRs,
102 MSHRQueue_WriteBuffer
103 };
104
105 public:
106 /**
107 * Reasons for caches to be blocked.
108 */
109 enum BlockedCause {
110 Blocked_NoMSHRs = MSHRQueue_MSHRs,
111 Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
112 Blocked_NoTargets,
113 NUM_BLOCKED_CAUSES
114 };
115
116 protected:
117
118 /**
119 * A cache master port is used for the memory-side port of the
120 * cache, and in addition to the basic timing port that only sends
121 * response packets through a transmit list, it also offers the
122 * ability to schedule and send request packets (requests &
123 * writebacks). The send event is scheduled through schedSendEvent,
124 * and the sendDeferredPacket of the timing port is modified to
125 * consider both the transmit list and the requests from the MSHR.
126 */
127 class CacheMasterPort : public QueuedMasterPort
128 {
129
130 public:
131
132 /**
133 * Schedule a send of a request packet (from the MSHR). Note
134 * that we could already have a retry outstanding.
135 */
136 void schedSendEvent(Tick time)
137 {
138 DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
139 reqQueue.schedSendEvent(time);
140 }
141
142 protected:
143
144 CacheMasterPort(const std::string &_name, BaseCache *_cache,
145 ReqPacketQueue &_reqQueue,
146 SnoopRespPacketQueue &_snoopRespQueue) :
147 QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
148 { }
149
150 /**
151 * Memory-side port always snoops.
152 *
153 * @return always true
154 */
155 virtual bool isSnooping() const { return true; }
156 };
157
158 /**
159 * Override the default behaviour of sendDeferredPacket to enable
160 * the memory-side cache port to also send requests based on the
161 * current MSHR status. This queue has a pointer to our specific
162 * cache implementation and is used by the MemSidePort.
163 */
164 class CacheReqPacketQueue : public ReqPacketQueue
165 {
166
167 protected:
168
169 BaseCache &cache;
170 SnoopRespPacketQueue &snoopRespQueue;
171
172 public:
173
174 CacheReqPacketQueue(BaseCache &cache, MasterPort &port,
175 SnoopRespPacketQueue &snoop_resp_queue,
176 const std::string &label) :
177 ReqPacketQueue(cache, port, label), cache(cache),
178 snoopRespQueue(snoop_resp_queue) { }
179
180 /**
181 * Override the normal sendDeferredPacket and do not only
182 * consider the transmit list (used for responses), but also
183 * requests.
184 */
185 virtual void sendDeferredPacket();
186
187 /**
188 * Check if there is a conflicting snoop response about to be
189 * send out, and if so simply stall any requests, and schedule
190 * a send event at the same time as the next snoop response is
191 * being sent out.
192 *
193 * @param pkt The packet to check for conflicts against.
194 */
195 bool checkConflictingSnoop(const PacketPtr pkt)
196 {
197 if (snoopRespQueue.checkConflict(pkt, cache.blkSize)) {
198 DPRINTF(CachePort, "Waiting for snoop response to be "
199 "sent\n");
200 Tick when = snoopRespQueue.deferredPacketReadyTime();
201 schedSendEvent(when);
202 return true;
203 }
204 return false;
205 }
206 };
207
208
209 /**
210 * The memory-side port extends the base cache master port with
211 * access functions for functional, atomic and timing snoops.
212 */
213 class MemSidePort : public CacheMasterPort
214 {
215 private:
216
217 /** The cache-specific queue. */
218 CacheReqPacketQueue _reqQueue;
219
220 SnoopRespPacketQueue _snoopRespQueue;
221
222 // a pointer to our specific cache implementation
223 BaseCache *cache;
224
225 protected:
226
227 virtual void recvTimingSnoopReq(PacketPtr pkt);
228
229 virtual bool recvTimingResp(PacketPtr pkt);
230
231 virtual Tick recvAtomicSnoop(PacketPtr pkt);
232
233 virtual void recvFunctionalSnoop(PacketPtr pkt);
234
235 public:
236
237 MemSidePort(const std::string &_name, BaseCache *_cache,
238 const std::string &_label);
239 };
240
241 /**
242 * A cache slave port is used for the CPU-side port of the cache,
243 * and it is basically a simple timing port that uses a transmit
244 * list for responses to the CPU (or connected master). In
245 * addition, it has the functionality to block the port for
246 * incoming requests. If blocked, the port will issue a retry once
247 * unblocked.
248 */
249 class CacheSlavePort : public QueuedSlavePort
250 {
251
252 public:
253
254 /** Do not accept any new requests. */
255 void setBlocked();
256
257 /** Return to normal operation and accept new requests. */
258 void clearBlocked();
259
260 bool isBlocked() const { return blocked; }
261
262 protected:
263
264 CacheSlavePort(const std::string &_name, BaseCache *_cache,
265 const std::string &_label);
266
267 /** A normal packet queue used to store responses. */
268 RespPacketQueue queue;
269
270 bool blocked;
271
272 bool mustSendRetry;
273
274 private:
275
276 void processSendRetry();
277
278 EventFunctionWrapper sendRetryEvent;
279
280 };
281
282 /**
283 * The CPU-side port extends the base cache slave port with access
284 * functions for functional, atomic and timing requests.
285 */
286 class CpuSidePort : public CacheSlavePort
287 {
288 private:
289
290 // a pointer to our specific cache implementation
291 BaseCache *cache;
292
293 protected:
294 virtual bool recvTimingSnoopResp(PacketPtr pkt) override;
295
296 virtual bool tryTiming(PacketPtr pkt) override;
297
298 virtual bool recvTimingReq(PacketPtr pkt) override;
299
300 virtual Tick recvAtomic(PacketPtr pkt) override;
301
302 virtual void recvFunctional(PacketPtr pkt) override;
303
304 virtual AddrRangeList getAddrRanges() const override;
305
306 public:
307
308 CpuSidePort(const std::string &_name, BaseCache *_cache,
309 const std::string &_label);
310
311 };
312
313 CpuSidePort cpuSidePort;
314 MemSidePort memSidePort;
315
316 protected:
317
318 /** Miss status registers */
319 MSHRQueue mshrQueue;
320
321 /** Write/writeback buffer */
322 WriteQueue writeBuffer;
323
324 /** Tag and data Storage */
325 BaseTags *tags;
326
327 /** Prefetcher */
328 BasePrefetcher *prefetcher;
329
330 /** To probe when a cache hit occurs */
331 ProbePointArg<PacketPtr> *ppHit;
332
333 /** To probe when a cache miss occurs */
334 ProbePointArg<PacketPtr> *ppMiss;
335
336 /** To probe when a cache fill occurs */
337 ProbePointArg<PacketPtr> *ppFill;
338
339 /**
340 * The writeAllocator drive optimizations for streaming writes.
341 * It first determines whether a WriteReq MSHR should be delayed,
342 * thus ensuring that we wait longer in cases when we are write
343 * coalescing and allowing all the bytes of the line to be written
344 * before the MSHR packet is sent downstream. This works in unison
345 * with the tracking in the MSHR to check if the entire line is
346 * written. The write mode also affects the behaviour on filling
347 * any whole-line writes. Normally the cache allocates the line
348 * when receiving the InvalidateResp, but after seeing enough
349 * consecutive lines we switch to using the tempBlock, and thus
350 * end up not allocating the line, and instead turning the
351 * whole-line write into a writeback straight away.
352 */
353 WriteAllocator * const writeAllocator;
354
355 /**
356 * Temporary cache block for occasional transitory use. We use
357 * the tempBlock to fill when allocation fails (e.g., when there
358 * is an outstanding request that accesses the victim block) or
359 * when we want to avoid allocation (e.g., exclusive caches)
360 */
361 TempCacheBlk *tempBlock;
362
363 /**
364 * Upstream caches need this packet until true is returned, so
365 * hold it for deletion until a subsequent call
366 */
367 std::unique_ptr<Packet> pendingDelete;
368
369 /**
370 * Mark a request as in service (sent downstream in the memory
371 * system), effectively making this MSHR the ordering point.
372 */
373 void markInService(MSHR *mshr, bool pending_modified_resp)
374 {
375 bool wasFull = mshrQueue.isFull();
376 mshrQueue.markInService(mshr, pending_modified_resp);
377
378 if (wasFull && !mshrQueue.isFull()) {
379 clearBlocked(Blocked_NoMSHRs);
380 }
381 }
382
383 void markInService(WriteQueueEntry *entry)
384 {
385 bool wasFull = writeBuffer.isFull();
386 writeBuffer.markInService(entry);
387
388 if (wasFull && !writeBuffer.isFull()) {
389 clearBlocked(Blocked_NoWBBuffers);
390 }
391 }
392
393 /**
394 * Determine whether we should allocate on a fill or not. If this
395 * cache is mostly inclusive with regards to the upstream cache(s)
396 * we always allocate (for any non-forwarded and cacheable
397 * requests). In the case of a mostly exclusive cache, we allocate
398 * on fill if the packet did not come from a cache, thus if we:
399 * are dealing with a whole-line write (the latter behaves much
400 * like a writeback), the original target packet came from a
401 * non-caching source, or if we are performing a prefetch or LLSC.
402 *
403 * @param cmd Command of the incoming requesting packet
404 * @return Whether we should allocate on the fill
405 */
406 inline bool allocOnFill(MemCmd cmd) const
407 {
408 return clusivity == Enums::mostly_incl ||
409 cmd == MemCmd::WriteLineReq ||
410 cmd == MemCmd::ReadReq ||
411 cmd == MemCmd::WriteReq ||
412 cmd.isPrefetch() ||
413 cmd.isLLSC();
414 }
415
416 /**
417 * Regenerate block address using tags.
418 * Block address regeneration depends on whether we're using a temporary
419 * block or not.
420 *
421 * @param blk The block to regenerate address.
422 * @return The block's address.
423 */
424 Addr regenerateBlkAddr(CacheBlk* blk);
425
426 /**
427 * Calculate latency of accesses that only touch the tag array.
428 * @sa calculateAccessLatency
429 *
430 * @param delay The delay until the packet's metadata is present.
431 * @param lookup_lat Latency of the respective tag lookup.
432 * @return The number of ticks that pass due to a tag-only access.
433 */
434 Cycles calculateTagOnlyLatency(const uint32_t delay,
435 const Cycles lookup_lat) const;
436 /**
437 * Calculate access latency in ticks given a tag lookup latency, and
438 * whether access was a hit or miss.
439 *
440 * @param blk The cache block that was accessed.
441 * @param delay The delay until the packet's metadata is present.
442 * @param lookup_lat Latency of the respective tag lookup.
443 * @return The number of ticks that pass due to a block access.
444 */
445 Cycles calculateAccessLatency(const CacheBlk* blk, const uint32_t delay,
446 const Cycles lookup_lat) const;
447
448 /**
449 * Does all the processing necessary to perform the provided request.
450 * @param pkt The memory request to perform.
451 * @param blk The cache block to be updated.
452 * @param lat The latency of the access.
453 * @param writebacks List for any writebacks that need to be performed.
454 * @return Boolean indicating whether the request was satisfied.
455 */
456 virtual bool access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
457 PacketList &writebacks);
458
459 /*
460 * Handle a timing request that hit in the cache
461 *
462 * @param ptk The request packet
463 * @param blk The referenced block
464 * @param request_time The tick at which the block lookup is compete
465 */
466 virtual void handleTimingReqHit(PacketPtr pkt, CacheBlk *blk,
467 Tick request_time);
468
469 /*
470 * Handle a timing request that missed in the cache
471 *
472 * Implementation specific handling for different cache
473 * implementations
474 *
475 * @param ptk The request packet
476 * @param blk The referenced block
477 * @param forward_time The tick at which we can process dependent requests
478 * @param request_time The tick at which the block lookup is compete
479 */
480 virtual void handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk,
481 Tick forward_time,
482 Tick request_time) = 0;
483
484 /*
485 * Handle a timing request that missed in the cache
486 *
487 * Common functionality across different cache implementations
488 *
489 * @param ptk The request packet
490 * @param blk The referenced block
491 * @param mshr Any existing mshr for the referenced cache block
492 * @param forward_time The tick at which we can process dependent requests
493 * @param request_time The tick at which the block lookup is compete
494 */
495 void handleTimingReqMiss(PacketPtr pkt, MSHR *mshr, CacheBlk *blk,
496 Tick forward_time, Tick request_time);
497
498 /**
499 * Performs the access specified by the request.
500 * @param pkt The request to perform.
501 */
502 virtual void recvTimingReq(PacketPtr pkt);
503
504 /**
505 * Handling the special case of uncacheable write responses to
506 * make recvTimingResp less cluttered.
507 */
508 void handleUncacheableWriteResp(PacketPtr pkt);
509
510 /**
511 * Service non-deferred MSHR targets using the received response
512 *
513 * Iterates through the list of targets that can be serviced with
514 * the current response.
515 *
516 * @param mshr The MSHR that corresponds to the reponse
517 * @param pkt The response packet
518 * @param blk The reference block
519 */
520 virtual void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt,
521 CacheBlk *blk) = 0;
522
523 /**
524 * Handles a response (cache line fill/write ack) from the bus.
525 * @param pkt The response packet
526 */
527 virtual void recvTimingResp(PacketPtr pkt);
528
529 /**
530 * Snoops bus transactions to maintain coherence.
531 * @param pkt The current bus transaction.
532 */
533 virtual void recvTimingSnoopReq(PacketPtr pkt) = 0;
534
535 /**
536 * Handle a snoop response.
537 * @param pkt Snoop response packet
538 */
539 virtual void recvTimingSnoopResp(PacketPtr pkt) = 0;
540
541 /**
542 * Handle a request in atomic mode that missed in this cache
543 *
544 * Creates a downstream request, sends it to the memory below and
545 * handles the response. As we are in atomic mode all operations
546 * are performed immediately.
547 *
548 * @param pkt The packet with the requests
549 * @param blk The referenced block
550 * @param writebacks A list with packets for any performed writebacks
551 * @return Cycles for handling the request
552 */
553 virtual Cycles handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
554 PacketList &writebacks) = 0;
555
556 /**
557 * Performs the access specified by the request.
558 * @param pkt The request to perform.
559 * @return The number of ticks required for the access.
560 */
561 virtual Tick recvAtomic(PacketPtr pkt);
562
563 /**
564 * Snoop for the provided request in the cache and return the estimated
565 * time taken.
566 * @param pkt The memory request to snoop
567 * @return The number of ticks required for the snoop.
568 */
569 virtual Tick recvAtomicSnoop(PacketPtr pkt) = 0;
570
571 /**
572 * Performs the access specified by the request.
573 *
574 * @param pkt The request to perform.
575 * @param fromCpuSide from the CPU side port or the memory side port
576 */
577 virtual void functionalAccess(PacketPtr pkt, bool from_cpu_side);
578
579 /**
580 * Handle doing the Compare and Swap function for SPARC.
581 */
582 void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
583
584 /**
585 * Return the next queue entry to service, either a pending miss
586 * from the MSHR queue, a buffered write from the write buffer, or
587 * something from the prefetcher. This function is responsible
588 * for prioritizing among those sources on the fly.
589 */
590 QueueEntry* getNextQueueEntry();
591
592 /**
593 * Insert writebacks into the write buffer
594 */
595 virtual void doWritebacks(PacketList& writebacks, Tick forward_time) = 0;
596
597 /**
598 * Send writebacks down the memory hierarchy in atomic mode
599 */
600 virtual void doWritebacksAtomic(PacketList& writebacks) = 0;
601
602 /**
603 * Create an appropriate downstream bus request packet.
604 *
605 * Creates a new packet with the request to be send to the memory
606 * below, or nullptr if the current request in cpu_pkt should just
607 * be forwarded on.
608 *
609 * @param cpu_pkt The miss packet that needs to be satisfied.
610 * @param blk The referenced block, can be nullptr.
611 * @param needs_writable Indicates that the block must be writable
612 * even if the request in cpu_pkt doesn't indicate that.
613 * @param is_whole_line_write True if there are writes for the
614 * whole line
615 * @return A packet send to the memory below
616 */
617 virtual PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
618 bool needs_writable,
619 bool is_whole_line_write) const = 0;
620
621 /**
622 * Determine if clean lines should be written back or not. In
623 * cases where a downstream cache is mostly inclusive we likely
624 * want it to act as a victim cache also for lines that have not
625 * been modified. Hence, we cannot simply drop the line (or send a
626 * clean evict), but rather need to send the actual data.
627 */
628 const bool writebackClean;
629
630 /**
631 * Writebacks from the tempBlock, resulting on the response path
632 * in atomic mode, must happen after the call to recvAtomic has
633 * finished (for the right ordering of the packets). We therefore
634 * need to hold on to the packets, and have a method and an event
635 * to send them.
636 */
637 PacketPtr tempBlockWriteback;
638
639 /**
640 * Send the outstanding tempBlock writeback. To be called after
641 * recvAtomic finishes in cases where the block we filled is in
642 * fact the tempBlock, and now needs to be written back.
643 */
644 void writebackTempBlockAtomic() {
645 assert(tempBlockWriteback != nullptr);
646 PacketList writebacks{tempBlockWriteback};
647 doWritebacksAtomic(writebacks);
648 tempBlockWriteback = nullptr;
649 }
650
651 /**
652 * An event to writeback the tempBlock after recvAtomic
653 * finishes. To avoid other calls to recvAtomic getting in
654 * between, we create this event with a higher priority.
655 */
656 EventFunctionWrapper writebackTempBlockAtomicEvent;
657
658 /**
659 * Perform any necessary updates to the block and perform any data
660 * exchange between the packet and the block. The flags of the
661 * packet are also set accordingly.
662 *
663 * @param pkt Request packet from upstream that hit a block
664 * @param blk Cache block that the packet hit
665 * @param deferred_response Whether this request originally missed
666 * @param pending_downgrade Whether the writable flag is to be removed
667 */
668 virtual void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
669 bool deferred_response = false,
670 bool pending_downgrade = false);
671
672 /**
673 * Maintain the clusivity of this cache by potentially
674 * invalidating a block. This method works in conjunction with
675 * satisfyRequest, but is separate to allow us to handle all MSHR
676 * targets before potentially dropping a block.
677 *
678 * @param from_cache Whether we have dealt with a packet from a cache
679 * @param blk The block that should potentially be dropped
680 */
681 void maintainClusivity(bool from_cache, CacheBlk *blk);
682
683 /**
684 * Handle a fill operation caused by a received packet.
685 *
686 * Populates a cache block and handles all outstanding requests for the
687 * satisfied fill request. This version takes two memory requests. One
688 * contains the fill data, the other is an optional target to satisfy.
689 * Note that the reason we return a list of writebacks rather than
690 * inserting them directly in the write buffer is that this function
691 * is called by both atomic and timing-mode accesses, and in atomic
692 * mode we don't mess with the write buffer (we just perform the
693 * writebacks atomically once the original request is complete).
694 *
695 * @param pkt The memory request with the fill data.
696 * @param blk The cache block if it already exists.
697 * @param writebacks List for any writebacks that need to be performed.
698 * @param allocate Whether to allocate a block or use the temp block
699 * @return Pointer to the new cache block.
700 */
701 CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
702 PacketList &writebacks, bool allocate);
703
704 /**
705 * Allocate a new block and perform any necessary writebacks
706 *
707 * Find a victim block and if necessary prepare writebacks for any
708 * existing data. May return nullptr if there are no replaceable
709 * blocks. If a replaceable block is found, it inserts the new block in
710 * its place. The new block, however, is not set as valid yet.
711 *
712 * @param pkt Packet holding the address to update
713 * @param writebacks A list of writeback packets for the evicted blocks
714 * @return the allocated block
715 */
716 CacheBlk *allocateBlock(const PacketPtr pkt, PacketList &writebacks);
717 /**
718 * Evict a cache block.
719 *
720 * Performs a writeback if necesssary and invalidates the block
721 *
722 * @param blk Block to invalidate
723 * @return A packet with the writeback, can be nullptr
724 */
725 M5_NODISCARD virtual PacketPtr evictBlock(CacheBlk *blk) = 0;
726
727 /**
728 * Evict a cache block.
729 *
730 * Performs a writeback if necesssary and invalidates the block
731 *
732 * @param blk Block to invalidate
733 * @param writebacks Return a list of packets with writebacks
734 */
735 void evictBlock(CacheBlk *blk, PacketList &writebacks);
736
737 /**
738 * Invalidate a cache block.
739 *
740 * @param blk Block to invalidate
741 */
742 void invalidateBlock(CacheBlk *blk);
743
744 /**
745 * Create a writeback request for the given block.
746 *
747 * @param blk The block to writeback.
748 * @return The writeback request for the block.
749 */
750 PacketPtr writebackBlk(CacheBlk *blk);
751
752 /**
753 * Create a writeclean request for the given block.
754 *
755 * Creates a request that writes the block to the cache below
756 * without evicting the block from the current cache.
757 *
758 * @param blk The block to write clean.
759 * @param dest The destination of the write clean operation.
760 * @param id Use the given packet id for the write clean operation.
761 * @return The generated write clean packet.
762 */
763 PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id);
764
765 /**
766 * Write back dirty blocks in the cache using functional accesses.
767 */
768 virtual void memWriteback() override;
769
770 /**
771 * Invalidates all blocks in the cache.
772 *
773 * @warn Dirty cache lines will not be written back to
774 * memory. Make sure to call functionalWriteback() first if you
775 * want the to write them to memory.
776 */
777 virtual void memInvalidate() override;
778
779 /**
780 * Determine if there are any dirty blocks in the cache.
781 *
782 * @return true if at least one block is dirty, false otherwise.
783 */
784 bool isDirty() const;
785
786 /**
787 * Determine if an address is in the ranges covered by this
788 * cache. This is useful to filter snoops.
789 *
790 * @param addr Address to check against
791 *
792 * @return If the address in question is in range
793 */
794 bool inRange(Addr addr) const;
795
796 /**
797 * Find next request ready time from among possible sources.
798 */
799 Tick nextQueueReadyTime() const;
800
801 /** Block size of this cache */
802 const unsigned blkSize;
803
804 /**
805 * The latency of tag lookup of a cache. It occurs when there is
806 * an access to the cache.
807 */
808 const Cycles lookupLatency;
809
810 /**
811 * The latency of data access of a cache. It occurs when there is
812 * an access to the cache.
813 */
814 const Cycles dataLatency;
815
816 /**
817 * This is the forward latency of the cache. It occurs when there
818 * is a cache miss and a request is forwarded downstream, in
819 * particular an outbound miss.
820 */
821 const Cycles forwardLatency;
822
823 /** The latency to fill a cache block */
824 const Cycles fillLatency;
825
826 /**
827 * The latency of sending reponse to its upper level cache/core on
828 * a linefill. The responseLatency parameter captures this
829 * latency.
830 */
831 const Cycles responseLatency;
832
833 /**
834 * Whether tags and data are accessed sequentially.
835 */
836 const bool sequentialAccess;
837
838 /** The number of targets for each MSHR. */
839 const int numTarget;
840
841 /** Do we forward snoops from mem side port through to cpu side port? */
842 bool forwardSnoops;
843
844 /**
845 * Clusivity with respect to the upstream cache, determining if we
846 * fill into both this cache and the cache above on a miss. Note
847 * that we currently do not support strict clusivity policies.
848 */
849 const Enums::Clusivity clusivity;
850
851 /**
852 * Is this cache read only, for example the instruction cache, or
853 * table-walker cache. A cache that is read only should never see
854 * any writes, and should never get any dirty data (and hence
855 * never have to do any writebacks).
856 */
857 const bool isReadOnly;
858
859 /**
860 * Bit vector of the blocking reasons for the access path.
861 * @sa #BlockedCause
862 */
863 uint8_t blocked;
864
865 /** Increasing order number assigned to each incoming request. */
866 uint64_t order;
867
868 /** Stores time the cache blocked for statistics. */
869 Cycles blockedCycle;
870
871 /** Pointer to the MSHR that has no targets. */
872 MSHR *noTargetMSHR;
873
874 /** The number of misses to trigger an exit event. */
875 Counter missCount;
876
877 /**
878 * The address range to which the cache responds on the CPU side.
879 * Normally this is all possible memory addresses. */
880 const AddrRangeList addrRanges;
881
882 public:
883 /** System we are currently operating in. */
884 System *system;
885
886 // Statistics
887 /**
888 * @addtogroup CacheStatistics
889 * @{
890 */
891
892 /** Number of hits per thread for each type of command.
893 @sa Packet::Command */
894 Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
895 /** Number of hits for demand accesses. */
896 Stats::Formula demandHits;
897 /** Number of hit for all accesses. */
898 Stats::Formula overallHits;
899
900 /** Number of misses per thread for each type of command.
901 @sa Packet::Command */
902 Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
903 /** Number of misses for demand accesses. */
904 Stats::Formula demandMisses;
905 /** Number of misses for all accesses. */
906 Stats::Formula overallMisses;
907
908 /**
909 * Total number of cycles per thread/command spent waiting for a miss.
910 * Used to calculate the average miss latency.
911 */
912 Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
913 /** Total number of cycles spent waiting for demand misses. */
914 Stats::Formula demandMissLatency;
915 /** Total number of cycles spent waiting for all misses. */
916 Stats::Formula overallMissLatency;
917
918 /** The number of accesses per command and thread. */
919 Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
920 /** The number of demand accesses. */
921 Stats::Formula demandAccesses;
922 /** The number of overall accesses. */
923 Stats::Formula overallAccesses;
924
925 /** The miss rate per command and thread. */
926 Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
927 /** The miss rate of all demand accesses. */
928 Stats::Formula demandMissRate;
929 /** The miss rate for all accesses. */
930 Stats::Formula overallMissRate;
931
932 /** The average miss latency per command and thread. */
933 Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
934 /** The average miss latency for demand misses. */
935 Stats::Formula demandAvgMissLatency;
936 /** The average miss latency for all misses. */
937 Stats::Formula overallAvgMissLatency;
938
939 /** The total number of cycles blocked for each blocked cause. */
940 Stats::Vector blocked_cycles;
941 /** The number of times this cache blocked for each blocked cause. */
942 Stats::Vector blocked_causes;
943
944 /** The average number of cycles blocked for each blocked cause. */
945 Stats::Formula avg_blocked;
946
947 /** The number of times a HW-prefetched block is evicted w/o reference. */
948 Stats::Scalar unusedPrefetches;
949
950 /** Number of blocks written back per thread. */
951 Stats::Vector writebacks;
952
953 /** Number of misses that hit in the MSHRs per command and thread. */
954 Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
955 /** Demand misses that hit in the MSHRs. */
956 Stats::Formula demandMshrHits;
957 /** Total number of misses that hit in the MSHRs. */
958 Stats::Formula overallMshrHits;
959
960 /** Number of misses that miss in the MSHRs, per command and thread. */
961 Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
962 /** Demand misses that miss in the MSHRs. */
963 Stats::Formula demandMshrMisses;
964 /** Total number of misses that miss in the MSHRs. */
965 Stats::Formula overallMshrMisses;
966
967 /** Number of misses that miss in the MSHRs, per command and thread. */
968 Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
969 /** Total number of misses that miss in the MSHRs. */
970 Stats::Formula overallMshrUncacheable;
971
972 /** Total cycle latency of each MSHR miss, per command and thread. */
973 Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
974 /** Total cycle latency of demand MSHR misses. */
975 Stats::Formula demandMshrMissLatency;
976 /** Total cycle latency of overall MSHR misses. */
977 Stats::Formula overallMshrMissLatency;
978
979 /** Total cycle latency of each MSHR miss, per command and thread. */
980 Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
981 /** Total cycle latency of overall MSHR misses. */
982 Stats::Formula overallMshrUncacheableLatency;
983
984#if 0
985 /** The total number of MSHR accesses per command and thread. */
986 Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
987 /** The total number of demand MSHR accesses. */
988 Stats::Formula demandMshrAccesses;
989 /** The total number of MSHR accesses. */
990 Stats::Formula overallMshrAccesses;
991#endif
992
993 /** The miss rate in the MSHRs pre command and thread. */
994 Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
995 /** The demand miss rate in the MSHRs. */
996 Stats::Formula demandMshrMissRate;
997 /** The overall miss rate in the MSHRs. */
998 Stats::Formula overallMshrMissRate;
999
1000 /** The average latency of an MSHR miss, per command and thread. */
1001 Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
1002 /** The average latency of a demand MSHR miss. */
1003 Stats::Formula demandAvgMshrMissLatency;
1004 /** The average overall latency of an MSHR miss. */
1005 Stats::Formula overallAvgMshrMissLatency;
1006
1007 /** The average latency of an MSHR miss, per command and thread. */
1008 Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
1009 /** The average overall latency of an MSHR miss. */
1010 Stats::Formula overallAvgMshrUncacheableLatency;
1011
1012 /** Number of replacements of valid blocks. */
1013 Stats::Scalar replacements;
1014
1015 /**
1016 * @}
1017 */
1018
1019 /**
1020 * Register stats for this object.
1021 */
1022 void regStats() override;
1023
1024 /** Registers probes. */
1025 void regProbePoints() override;
1026
1027 public:
1028 BaseCache(const BaseCacheParams *p, unsigned blk_size);
1029 ~BaseCache();
1030
1031 void init() override;
1032
1033 Port &getPort(const std::string &if_name,
1034 PortID idx=InvalidPortID) override;
1035
1036 /**
1037 * Query block size of a cache.
1038 * @return The block size
1039 */
1040 unsigned
1041 getBlockSize() const
1042 {
1043 return blkSize;
1044 }
1045
1046 const AddrRangeList &getAddrRanges() const { return addrRanges; }
1047
1048 MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
1049 {
1050 MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
1051 pkt, time, order++,
1052 allocOnFill(pkt->cmd));
1053
1054 if (mshrQueue.isFull()) {
1055 setBlocked((BlockedCause)MSHRQueue_MSHRs);
1056 }
1057
1058 if (sched_send) {
1059 // schedule the send
1060 schedMemSideSendEvent(time);
1061 }
1062
1063 return mshr;
1064 }
1065
1066 void allocateWriteBuffer(PacketPtr pkt, Tick time)
1067 {
1068 // should only see writes or clean evicts here
1069 assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);
1070
1071 Addr blk_addr = pkt->getBlockAddr(blkSize);
1072
1073 WriteQueueEntry *wq_entry =
1074 writeBuffer.findMatch(blk_addr, pkt->isSecure());
1075 if (wq_entry && !wq_entry->inService) {
1076 DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
1077 }
1078
1079 writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);
1080
1081 if (writeBuffer.isFull()) {
1082 setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
1083 }
1084
1085 // schedule the send
1086 schedMemSideSendEvent(time);
1087 }
1088
1089 /**
1090 * Returns true if the cache is blocked for accesses.
1091 */
1092 bool isBlocked() const
1093 {
1094 return blocked != 0;
1095 }
1096
1097 /**
1098 * Marks the access path of the cache as blocked for the given cause. This
1099 * also sets the blocked flag in the slave interface.
1100 * @param cause The reason for the cache blocking.
1101 */
1102 void setBlocked(BlockedCause cause)
1103 {
1104 uint8_t flag = 1 << cause;
1105 if (blocked == 0) {
1106 blocked_causes[cause]++;
1107 blockedCycle = curCycle();
1108 cpuSidePort.setBlocked();
1109 }
1110 blocked |= flag;
1111 DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
1112 }
1113
1114 /**
1115 * Marks the cache as unblocked for the given cause. This also clears the
1116 * blocked flags in the appropriate interfaces.
1117 * @param cause The newly unblocked cause.
1118 * @warning Calling this function can cause a blocked request on the bus to
1119 * access the cache. The cache must be in a state to handle that request.
1120 */
1121 void clearBlocked(BlockedCause cause)
1122 {
1123 uint8_t flag = 1 << cause;
1124 blocked &= ~flag;
1125 DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
1126 if (blocked == 0) {
1127 blocked_cycles[cause] += curCycle() - blockedCycle;
1128 cpuSidePort.clearBlocked();
1129 }
1130 }
1131
1132 /**
1133 * Schedule a send event for the memory-side port. If already
1134 * scheduled, this may reschedule the event at an earlier
1135 * time. When the specified time is reached, the port is free to
1136 * send either a response, a request, or a prefetch request.
1137 *
1138 * @param time The time when to attempt sending a packet.
1139 */
1140 void schedMemSideSendEvent(Tick time)
1141 {
1142 memSidePort.schedSendEvent(time);
1143 }
1144
1145 bool inCache(Addr addr, bool is_secure) const {
1146 return tags->findBlock(addr, is_secure);
1147 }
1148
1149 bool hasBeenPrefetched(Addr addr, bool is_secure) const {
1150 CacheBlk *block = tags->findBlock(addr, is_secure);
1151 if (block) {
1152 return block->wasPrefetched();
1153 } else {
1154 return false;
1155 }
1156 }
1157
1158 bool inMissQueue(Addr addr, bool is_secure) const {
1159 return mshrQueue.findMatch(addr, is_secure);
1160 }
1161
1162 void incMissCount(PacketPtr pkt)
1163 {
1164 assert(pkt->req->masterId() < system->maxMasters());
1165 misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
1166 pkt->req->incAccessDepth();
1167 if (missCount) {
1168 --missCount;
1169 if (missCount == 0)
1170 exitSimLoop("A cache reached the maximum miss count");
1171 }
1172 }
1173 void incHitCount(PacketPtr pkt)
1174 {
1175 assert(pkt->req->masterId() < system->maxMasters());
1176 hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
1177
1178 }
1179
1180 /**
1181 * Checks if the cache is coalescing writes
1182 *
1183 * @return True if the cache is coalescing writes
1184 */
1185 bool coalesce() const;
1186
1187
1188 /**
1189 * Cache block visitor that writes back dirty cache blocks using
1190 * functional writes.
1191 */
1192 void writebackVisitor(CacheBlk &blk);
1193
1194 /**
1195 * Cache block visitor that invalidates all blocks in the cache.
1196 *
1197 * @warn Dirty cache lines will not be written back to memory.
1198 */
1199 void invalidateVisitor(CacheBlk &blk);
1200
1201 /**
1202 * Take an MSHR, turn it into a suitable downstream packet, and
1203 * send it out. This construct allows a queue entry to choose a suitable
1204 * approach based on its type.
1205 *
1206 * @param mshr The MSHR to turn into a packet and send
1207 * @return True if the port is waiting for a retry
1208 */
1209 virtual bool sendMSHRQueuePacket(MSHR* mshr);
1210
1211 /**
1212 * Similar to sendMSHR, but for a write-queue entry
1213 * instead. Create the packet, and send it, and if successful also
1214 * mark the entry in service.
1215 *
1216 * @param wq_entry The write-queue entry to turn into a packet and send
1217 * @return True if the port is waiting for a retry
1218 */
1219 bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
1220
1221 /**
1222 * Serialize the state of the caches
1223 *
1224 * We currently don't support checkpointing cache state, so this panics.
1225 */
1226 void serialize(CheckpointOut &cp) const override;
1227 void unserialize(CheckpointIn &cp) override;
1228};
1229
1230/**
1231 * The write allocator inspects write packets and detects streaming
1232 * patterns. The write allocator supports a single stream where writes
1233 * are expected to access consecutive locations and keeps track of
1234 * size of the area covered by the concecutive writes in byteCount.
1235 *
1236 * 1) When byteCount has surpassed the coallesceLimit the mode
1237 * switches from ALLOCATE to COALESCE where writes should be delayed
1238 * until the whole block is written at which point a single packet
1239 * (whole line write) can service them.
1240 *
1241 * 2) When byteCount has also exceeded the noAllocateLimit (whole
1242 * line) we switch to NO_ALLOCATE when writes should not allocate in
1243 * the cache but rather send a whole line write to the memory below.
1244 */
1245class WriteAllocator : public SimObject {
1246 public:
1247 WriteAllocator(const WriteAllocatorParams *p) :
1248 SimObject(p),
1249 coalesceLimit(p->coalesce_limit * p->block_size),
1250 noAllocateLimit(p->no_allocate_limit * p->block_size),
1251 delayThreshold(p->delay_threshold)
1252 {
1253 reset();
1254 }
1255
1256 /**
1257 * Should writes be coalesced? This is true if the mode is set to
1258 * NO_ALLOCATE.
1259 *
1260 * @return return true if the cache should coalesce writes.
1261 */
1262 bool coalesce() const {
1263 return mode != WriteMode::ALLOCATE;
1264 }
1265
1266 /**
1267 * Should writes allocate?
1268 *
1269 * @return return true if the cache should not allocate for writes.
1270 */
1271 bool allocate() const {
1272 return mode != WriteMode::NO_ALLOCATE;
1273 }
1274
1275 /**
1276 * Reset the write allocator state, meaning that it allocates for
1277 * writes and has not recorded any information about qualifying
1278 * writes that might trigger a switch to coalescing and later no
1279 * allocation.
1280 */
1281 void reset() {
1282 mode = WriteMode::ALLOCATE;
1283 byteCount = 0;
1284 nextAddr = 0;
1285 }
1286
1287 /**
1288 * Access whether we need to delay the current write.
1289 *
1290 * @param blk_addr The block address the packet writes to
1291 * @return true if the current packet should be delayed
1292 */
1293 bool delay(Addr blk_addr) {
1294 if (delayCtr[blk_addr] > 0) {
1295 --delayCtr[blk_addr];
1296 return true;
1297 } else {
1298 return false;
1299 }
1300 }
1301
1302 /**
1303 * Clear delay counter for the input block
1304 *
1305 * @param blk_addr The accessed cache block
1306 */
1307 void resetDelay(Addr blk_addr) {
1308 delayCtr.erase(blk_addr);
1309 }
1310
1311 /**
1312 * Update the write mode based on the current write
1313 * packet. This method compares the packet's address with any
1314 * current stream, and updates the tracking and the mode
1315 * accordingly.
1316 *
1317 * @param write_addr Start address of the write request
1318 * @param write_size Size of the write request
1319 * @param blk_addr The block address that this packet writes to
1320 */
1321 void updateMode(Addr write_addr, unsigned write_size, Addr blk_addr);
1322
1323 private:
1324 /**
1325 * The current mode for write coalescing and allocation, either
1326 * normal operation (ALLOCATE), write coalescing (COALESCE), or
1327 * write coalescing without allocation (NO_ALLOCATE).
1328 */
1329 enum class WriteMode : char {
1330 ALLOCATE,
1331 COALESCE,
1332 NO_ALLOCATE,
1333 };
1334 WriteMode mode;
1335
1336 /** Address to match writes against to detect streams. */
1337 Addr nextAddr;
1338
1339 /**
1340 * Bytes written contiguously. Saturating once we no longer
1341 * allocate.
1342 */
1343 uint32_t byteCount;
1344
1345 /**
1346 * Limits for when to switch between the different write modes.
1347 */
1348 const uint32_t coalesceLimit;
1349 const uint32_t noAllocateLimit;
1350 /**
1351 * The number of times the allocator will delay an WriteReq MSHR.
1352 */
1353 const uint32_t delayThreshold;
1354
1355 /**
1356 * Keep track of the number of times the allocator has delayed an
1357 * WriteReq MSHR.
1358 */
1359 std::unordered_map<Addr, Counter> delayCtr;
1360};
1361
1362#endif //__MEM_CACHE_BASE_HH__
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