1/*
2 * Copyright (c) 2012-2013, 2015-2016, 2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Erik Hallnor
41 * Steve Reinhardt
42 * Ron Dreslinski
43 * Andreas Hansson
44 * Nikos Nikoleris
45 */
46
47/**
48 * @file
49 * Declares a basic cache interface BaseCache.
50 */
51
52#ifndef __MEM_CACHE_BASE_HH__
53#define __MEM_CACHE_BASE_HH__
54
55#include <cassert>
56#include <cstdint>
57#include <string>
58
59#include "base/addr_range.hh"
60#include "base/statistics.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CachePort.hh"
65#include "enums/Clusivity.hh"
66#include "mem/cache/cache_blk.hh"
67#include "mem/cache/mshr_queue.hh"
68#include "mem/cache/tags/base.hh"
69#include "mem/cache/write_queue.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/mem_object.hh"
72#include "mem/packet.hh"
73#include "mem/packet_queue.hh"
74#include "mem/qport.hh"
75#include "mem/request.hh"
76#include "params/WriteAllocator.hh"
77#include "sim/eventq.hh"
78#include "sim/serialize.hh"
79#include "sim/sim_exit.hh"
80#include "sim/system.hh"
81
82class BaseMasterPort;
83class BasePrefetcher;
84class BaseSlavePort;
85class MSHR;
86class MasterPort;
87class QueueEntry;
88struct BaseCacheParams;
89
90/**
91 * A basic cache interface. Implements some common functions for speed.
92 */
93class BaseCache : public MemObject
94{
95 protected:
96 /**
97 * Indexes to enumerate the MSHR queues.
98 */
99 enum MSHRQueueIndex {
100 MSHRQueue_MSHRs,
101 MSHRQueue_WriteBuffer
102 };
103
104 public:
105 /**
106 * Reasons for caches to be blocked.
107 */
108 enum BlockedCause {
109 Blocked_NoMSHRs = MSHRQueue_MSHRs,
110 Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
111 Blocked_NoTargets,
112 NUM_BLOCKED_CAUSES
113 };
114
115 protected:
116
117 /**
118 * A cache master port is used for the memory-side port of the
119 * cache, and in addition to the basic timing port that only sends
120 * response packets through a transmit list, it also offers the
121 * ability to schedule and send request packets (requests &
122 * writebacks). The send event is scheduled through schedSendEvent,
123 * and the sendDeferredPacket of the timing port is modified to
124 * consider both the transmit list and the requests from the MSHR.
125 */
126 class CacheMasterPort : public QueuedMasterPort
127 {
128
129 public:
130
131 /**
132 * Schedule a send of a request packet (from the MSHR). Note
133 * that we could already have a retry outstanding.
134 */
135 void schedSendEvent(Tick time)
136 {
137 DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
138 reqQueue.schedSendEvent(time);
139 }
140
141 protected:
142
143 CacheMasterPort(const std::string &_name, BaseCache *_cache,
144 ReqPacketQueue &_reqQueue,
145 SnoopRespPacketQueue &_snoopRespQueue) :
146 QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
147 { }
148
149 /**
150 * Memory-side port always snoops.
151 *
152 * @return always true
153 */
154 virtual bool isSnooping() const { return true; }
155 };
156
157 /**
158 * Override the default behaviour of sendDeferredPacket to enable
159 * the memory-side cache port to also send requests based on the
160 * current MSHR status. This queue has a pointer to our specific
161 * cache implementation and is used by the MemSidePort.
162 */
163 class CacheReqPacketQueue : public ReqPacketQueue
164 {
165
166 protected:
167
168 BaseCache &cache;
169 SnoopRespPacketQueue &snoopRespQueue;
170
171 public:
172
173 CacheReqPacketQueue(BaseCache &cache, MasterPort &port,
174 SnoopRespPacketQueue &snoop_resp_queue,
175 const std::string &label) :
176 ReqPacketQueue(cache, port, label), cache(cache),
177 snoopRespQueue(snoop_resp_queue) { }
178
179 /**
180 * Override the normal sendDeferredPacket and do not only
181 * consider the transmit list (used for responses), but also
182 * requests.
183 */
184 virtual void sendDeferredPacket();
185
186 /**
187 * Check if there is a conflicting snoop response about to be
188 * send out, and if so simply stall any requests, and schedule
189 * a send event at the same time as the next snoop response is
190 * being sent out.
191 */
192 bool checkConflictingSnoop(Addr addr)
193 {
194 if (snoopRespQueue.hasAddr(addr)) {
195 DPRINTF(CachePort, "Waiting for snoop response to be "
196 "sent\n");
197 Tick when = snoopRespQueue.deferredPacketReadyTime();
198 schedSendEvent(when);
199 return true;
200 }
201 return false;
202 }
203 };
204
205
206 /**
207 * The memory-side port extends the base cache master port with
208 * access functions for functional, atomic and timing snoops.
209 */
210 class MemSidePort : public CacheMasterPort
211 {
212 private:
213
214 /** The cache-specific queue. */
215 CacheReqPacketQueue _reqQueue;
216
217 SnoopRespPacketQueue _snoopRespQueue;
218
219 // a pointer to our specific cache implementation
220 BaseCache *cache;
221
222 protected:
223
224 virtual void recvTimingSnoopReq(PacketPtr pkt);
225
226 virtual bool recvTimingResp(PacketPtr pkt);
227
228 virtual Tick recvAtomicSnoop(PacketPtr pkt);
229
230 virtual void recvFunctionalSnoop(PacketPtr pkt);
231
232 public:
233
234 MemSidePort(const std::string &_name, BaseCache *_cache,
235 const std::string &_label);
236 };
237
238 /**
239 * A cache slave port is used for the CPU-side port of the cache,
240 * and it is basically a simple timing port that uses a transmit
241 * list for responses to the CPU (or connected master). In
242 * addition, it has the functionality to block the port for
243 * incoming requests. If blocked, the port will issue a retry once
244 * unblocked.
245 */
246 class CacheSlavePort : public QueuedSlavePort
247 {
248
249 public:
250
251 /** Do not accept any new requests. */
252 void setBlocked();
253
254 /** Return to normal operation and accept new requests. */
255 void clearBlocked();
256
257 bool isBlocked() const { return blocked; }
258
259 protected:
260
261 CacheSlavePort(const std::string &_name, BaseCache *_cache,
262 const std::string &_label);
263
264 /** A normal packet queue used to store responses. */
265 RespPacketQueue queue;
266
267 bool blocked;
268
269 bool mustSendRetry;
270
271 private:
272
273 void processSendRetry();
274
275 EventFunctionWrapper sendRetryEvent;
276
277 };
278
279 /**
280 * The CPU-side port extends the base cache slave port with access
281 * functions for functional, atomic and timing requests.
282 */
283 class CpuSidePort : public CacheSlavePort
284 {
285 private:
286
287 // a pointer to our specific cache implementation
288 BaseCache *cache;
289
290 protected:
291 virtual bool recvTimingSnoopResp(PacketPtr pkt) override;
292
293 virtual bool tryTiming(PacketPtr pkt) override;
294
295 virtual bool recvTimingReq(PacketPtr pkt) override;
296
297 virtual Tick recvAtomic(PacketPtr pkt) override;
298
299 virtual void recvFunctional(PacketPtr pkt) override;
300
301 virtual AddrRangeList getAddrRanges() const override;
302
303 public:
304
305 CpuSidePort(const std::string &_name, BaseCache *_cache,
306 const std::string &_label);
307
308 };
309
310 CpuSidePort cpuSidePort;
311 MemSidePort memSidePort;
312
313 protected:
314
315 /** Miss status registers */
316 MSHRQueue mshrQueue;
317
318 /** Write/writeback buffer */
319 WriteQueue writeBuffer;
320
321 /** Tag and data Storage */
322 BaseTags *tags;
323
324 /** Prefetcher */
325 BasePrefetcher *prefetcher;
326
327 /**
328 * Notify the prefetcher on every access, not just misses.
329 */
330 const bool prefetchOnAccess;
331
332 /**
333 * The writeAllocator drive optimizations for streaming writes.
334 * It first determines whether a WriteReq MSHR should be delayed,
335 * thus ensuring that we wait longer in cases when we are write
336 * coalescing and allowing all the bytes of the line to be written
337 * before the MSHR packet is sent downstream. This works in unison
338 * with the tracking in the MSHR to check if the entire line is
339 * written. The write mode also affects the behaviour on filling
340 * any whole-line writes. Normally the cache allocates the line
341 * when receiving the InvalidateResp, but after seeing enough
342 * consecutive lines we switch to using the tempBlock, and thus
343 * end up not allocating the line, and instead turning the
344 * whole-line write into a writeback straight away.
345 */
346 WriteAllocator * const writeAllocator;
347
348 /**
349 * Temporary cache block for occasional transitory use. We use
350 * the tempBlock to fill when allocation fails (e.g., when there
351 * is an outstanding request that accesses the victim block) or
352 * when we want to avoid allocation (e.g., exclusive caches)
353 */
354 TempCacheBlk *tempBlock;
355
356 /**
357 * Upstream caches need this packet until true is returned, so
358 * hold it for deletion until a subsequent call
359 */
360 std::unique_ptr<Packet> pendingDelete;
361
362 /**
363 * Mark a request as in service (sent downstream in the memory
364 * system), effectively making this MSHR the ordering point.
365 */
366 void markInService(MSHR *mshr, bool pending_modified_resp)
367 {
368 bool wasFull = mshrQueue.isFull();
369 mshrQueue.markInService(mshr, pending_modified_resp);
370
371 if (wasFull && !mshrQueue.isFull()) {
372 clearBlocked(Blocked_NoMSHRs);
373 }
374 }
375
376 void markInService(WriteQueueEntry *entry)
377 {
378 bool wasFull = writeBuffer.isFull();
379 writeBuffer.markInService(entry);
380
381 if (wasFull && !writeBuffer.isFull()) {
382 clearBlocked(Blocked_NoWBBuffers);
383 }
384 }
385
386 /**
387 * Determine whether we should allocate on a fill or not. If this
388 * cache is mostly inclusive with regards to the upstream cache(s)
389 * we always allocate (for any non-forwarded and cacheable
390 * requests). In the case of a mostly exclusive cache, we allocate
391 * on fill if the packet did not come from a cache, thus if we:
392 * are dealing with a whole-line write (the latter behaves much
393 * like a writeback), the original target packet came from a
394 * non-caching source, or if we are performing a prefetch or LLSC.
395 *
396 * @param cmd Command of the incoming requesting packet
397 * @return Whether we should allocate on the fill
398 */
399 inline bool allocOnFill(MemCmd cmd) const
400 {
401 return clusivity == Enums::mostly_incl ||
402 cmd == MemCmd::WriteLineReq ||
403 cmd == MemCmd::ReadReq ||
404 cmd == MemCmd::WriteReq ||
405 cmd.isPrefetch() ||
406 cmd.isLLSC();
407 }
408
409 /**
410 * Regenerate block address using tags.
411 * Block address regeneration depends on whether we're using a temporary
412 * block or not.
413 *
414 * @param blk The block to regenerate address.
415 * @return The block's address.
416 */
417 Addr regenerateBlkAddr(CacheBlk* blk);
418
419 /**
420 * Does all the processing necessary to perform the provided request.
421 * @param pkt The memory request to perform.
422 * @param blk The cache block to be updated.
423 * @param lat The latency of the access.
424 * @param writebacks List for any writebacks that need to be performed.
425 * @return Boolean indicating whether the request was satisfied.
426 */
427 virtual bool access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
428 PacketList &writebacks);
429
430 /*
431 * Handle a timing request that hit in the cache
432 *
433 * @param ptk The request packet
434 * @param blk The referenced block
435 * @param request_time The tick at which the block lookup is compete
436 */
437 virtual void handleTimingReqHit(PacketPtr pkt, CacheBlk *blk,
438 Tick request_time);
439
440 /*
441 * Handle a timing request that missed in the cache
442 *
443 * Implementation specific handling for different cache
444 * implementations
445 *
446 * @param ptk The request packet
447 * @param blk The referenced block
448 * @param forward_time The tick at which we can process dependent requests
449 * @param request_time The tick at which the block lookup is compete
450 */
451 virtual void handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk,
452 Tick forward_time,
453 Tick request_time) = 0;
454
455 /*
456 * Handle a timing request that missed in the cache
457 *
458 * Common functionality across different cache implementations
459 *
460 * @param ptk The request packet
461 * @param blk The referenced block
462 * @param mshr Any existing mshr for the referenced cache block
463 * @param forward_time The tick at which we can process dependent requests
464 * @param request_time The tick at which the block lookup is compete
465 */
466 void handleTimingReqMiss(PacketPtr pkt, MSHR *mshr, CacheBlk *blk,
467 Tick forward_time, Tick request_time);
468
469 /**
470 * Performs the access specified by the request.
471 * @param pkt The request to perform.
472 */
473 virtual void recvTimingReq(PacketPtr pkt);
474
475 /**
476 * Handling the special case of uncacheable write responses to
477 * make recvTimingResp less cluttered.
478 */
479 void handleUncacheableWriteResp(PacketPtr pkt);
480
481 /**
482 * Service non-deferred MSHR targets using the received response
483 *
484 * Iterates through the list of targets that can be serviced with
485 * the current response. Any writebacks that need to performed
486 * must be appended to the writebacks parameter.
487 *
488 * @param mshr The MSHR that corresponds to the reponse
489 * @param pkt The response packet
490 * @param blk The reference block
491 * @param writebacks List of writebacks that need to be performed
492 */
493 virtual void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt,
494 CacheBlk *blk, PacketList& writebacks) = 0;
495
496 /**
497 * Handles a response (cache line fill/write ack) from the bus.
498 * @param pkt The response packet
499 */
500 virtual void recvTimingResp(PacketPtr pkt);
501
502 /**
503 * Snoops bus transactions to maintain coherence.
504 * @param pkt The current bus transaction.
505 */
506 virtual void recvTimingSnoopReq(PacketPtr pkt) = 0;
507
508 /**
509 * Handle a snoop response.
510 * @param pkt Snoop response packet
511 */
512 virtual void recvTimingSnoopResp(PacketPtr pkt) = 0;
513
514 /**
515 * Handle a request in atomic mode that missed in this cache
516 *
517 * Creates a downstream request, sends it to the memory below and
518 * handles the response. As we are in atomic mode all operations
519 * are performed immediately.
520 *
521 * @param pkt The packet with the requests
522 * @param blk The referenced block
523 * @param writebacks A list with packets for any performed writebacks
524 * @return Cycles for handling the request
525 */
526 virtual Cycles handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
527 PacketList &writebacks) = 0;
528
529 /**
530 * Performs the access specified by the request.
531 * @param pkt The request to perform.
532 * @return The number of ticks required for the access.
533 */
534 virtual Tick recvAtomic(PacketPtr pkt);
535
536 /**
537 * Snoop for the provided request in the cache and return the estimated
538 * time taken.
539 * @param pkt The memory request to snoop
540 * @return The number of ticks required for the snoop.
541 */
542 virtual Tick recvAtomicSnoop(PacketPtr pkt) = 0;
543
544 /**
545 * Performs the access specified by the request.
546 *
547 * @param pkt The request to perform.
548 * @param fromCpuSide from the CPU side port or the memory side port
549 */
550 virtual void functionalAccess(PacketPtr pkt, bool from_cpu_side);
551
552 /**
553 * Handle doing the Compare and Swap function for SPARC.
554 */
555 void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
556
557 /**
558 * Return the next queue entry to service, either a pending miss
559 * from the MSHR queue, a buffered write from the write buffer, or
560 * something from the prefetcher. This function is responsible
561 * for prioritizing among those sources on the fly.
562 */
563 QueueEntry* getNextQueueEntry();
564
565 /**
566 * Insert writebacks into the write buffer
567 */
568 virtual void doWritebacks(PacketList& writebacks, Tick forward_time) = 0;
569
570 /**
571 * Send writebacks down the memory hierarchy in atomic mode
572 */
573 virtual void doWritebacksAtomic(PacketList& writebacks) = 0;
574
575 /**
576 * Create an appropriate downstream bus request packet.
577 *
578 * Creates a new packet with the request to be send to the memory
579 * below, or nullptr if the current request in cpu_pkt should just
580 * be forwarded on.
581 *
582 * @param cpu_pkt The miss packet that needs to be satisfied.
583 * @param blk The referenced block, can be nullptr.
584 * @param needs_writable Indicates that the block must be writable
585 * even if the request in cpu_pkt doesn't indicate that.
586 * @param is_whole_line_write True if there are writes for the
587 * whole line
588 * @return A packet send to the memory below
589 */
590 virtual PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
591 bool needs_writable,
592 bool is_whole_line_write) const = 0;
593
594 /**
595 * Determine if clean lines should be written back or not. In
596 * cases where a downstream cache is mostly inclusive we likely
597 * want it to act as a victim cache also for lines that have not
598 * been modified. Hence, we cannot simply drop the line (or send a
599 * clean evict), but rather need to send the actual data.
600 */
601 const bool writebackClean;
602
603 /**
604 * Writebacks from the tempBlock, resulting on the response path
605 * in atomic mode, must happen after the call to recvAtomic has
606 * finished (for the right ordering of the packets). We therefore
607 * need to hold on to the packets, and have a method and an event
608 * to send them.
609 */
610 PacketPtr tempBlockWriteback;
611
612 /**
613 * Send the outstanding tempBlock writeback. To be called after
614 * recvAtomic finishes in cases where the block we filled is in
615 * fact the tempBlock, and now needs to be written back.
616 */
617 void writebackTempBlockAtomic() {
618 assert(tempBlockWriteback != nullptr);
619 PacketList writebacks{tempBlockWriteback};
620 doWritebacksAtomic(writebacks);
621 tempBlockWriteback = nullptr;
622 }
623
624 /**
625 * An event to writeback the tempBlock after recvAtomic
626 * finishes. To avoid other calls to recvAtomic getting in
627 * between, we create this event with a higher priority.
628 */
629 EventFunctionWrapper writebackTempBlockAtomicEvent;
630
631 /**
632 * Perform any necessary updates to the block and perform any data
633 * exchange between the packet and the block. The flags of the
634 * packet are also set accordingly.
635 *
636 * @param pkt Request packet from upstream that hit a block
637 * @param blk Cache block that the packet hit
638 * @param deferred_response Whether this request originally missed
639 * @param pending_downgrade Whether the writable flag is to be removed
640 */
641 virtual void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
642 bool deferred_response = false,
643 bool pending_downgrade = false);
644
645 /**
646 * Maintain the clusivity of this cache by potentially
647 * invalidating a block. This method works in conjunction with
648 * satisfyRequest, but is separate to allow us to handle all MSHR
649 * targets before potentially dropping a block.
650 *
651 * @param from_cache Whether we have dealt with a packet from a cache
652 * @param blk The block that should potentially be dropped
653 */
654 void maintainClusivity(bool from_cache, CacheBlk *blk);
655
656 /**
657 * Handle a fill operation caused by a received packet.
658 *
659 * Populates a cache block and handles all outstanding requests for the
660 * satisfied fill request. This version takes two memory requests. One
661 * contains the fill data, the other is an optional target to satisfy.
662 * Note that the reason we return a list of writebacks rather than
663 * inserting them directly in the write buffer is that this function
664 * is called by both atomic and timing-mode accesses, and in atomic
665 * mode we don't mess with the write buffer (we just perform the
666 * writebacks atomically once the original request is complete).
667 *
668 * @param pkt The memory request with the fill data.
669 * @param blk The cache block if it already exists.
670 * @param writebacks List for any writebacks that need to be performed.
671 * @param allocate Whether to allocate a block or use the temp block
672 * @return Pointer to the new cache block.
673 */
674 CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
675 PacketList &writebacks, bool allocate);
676
677 /**
678 * Allocate a new block and perform any necessary writebacks
679 *
680 * Find a victim block and if necessary prepare writebacks for any
681 * existing data. May return nullptr if there are no replaceable
682 * blocks. If a replaceable block is found, it inserts the new block in
683 * its place. The new block, however, is not set as valid yet.
684 *
685 * @param pkt Packet holding the address to update
686 * @param writebacks A list of writeback packets for the evicted blocks
687 * @return the allocated block
688 */
689 CacheBlk *allocateBlock(const PacketPtr pkt, PacketList &writebacks);
690 /**
691 * Evict a cache block.
692 *
693 * Performs a writeback if necesssary and invalidates the block
694 *
695 * @param blk Block to invalidate
696 * @return A packet with the writeback, can be nullptr
697 */
698 M5_NODISCARD virtual PacketPtr evictBlock(CacheBlk *blk) = 0;
699
700 /**
701 * Evict a cache block.
702 *
703 * Performs a writeback if necesssary and invalidates the block
704 *
705 * @param blk Block to invalidate
706 * @param writebacks Return a list of packets with writebacks
707 */
708 virtual void evictBlock(CacheBlk *blk, PacketList &writebacks) = 0;
709
710 /**
711 * Invalidate a cache block.
712 *
713 * @param blk Block to invalidate
714 */
715 void invalidateBlock(CacheBlk *blk);
716
717 /**
718 * Create a writeback request for the given block.
719 *
720 * @param blk The block to writeback.
721 * @return The writeback request for the block.
722 */
723 PacketPtr writebackBlk(CacheBlk *blk);
724
725 /**
726 * Create a writeclean request for the given block.
727 *
728 * Creates a request that writes the block to the cache below
729 * without evicting the block from the current cache.
730 *
731 * @param blk The block to write clean.
732 * @param dest The destination of the write clean operation.
733 * @param id Use the given packet id for the write clean operation.
734 * @return The generated write clean packet.
735 */
736 PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id);
737
738 /**
739 * Write back dirty blocks in the cache using functional accesses.
740 */
741 virtual void memWriteback() override;
742
743 /**
744 * Invalidates all blocks in the cache.
745 *
746 * @warn Dirty cache lines will not be written back to
747 * memory. Make sure to call functionalWriteback() first if you
748 * want the to write them to memory.
749 */
750 virtual void memInvalidate() override;
751
752 /**
753 * Determine if there are any dirty blocks in the cache.
754 *
755 * @return true if at least one block is dirty, false otherwise.
756 */
757 bool isDirty() const;
758
759 /**
760 * Determine if an address is in the ranges covered by this
761 * cache. This is useful to filter snoops.
762 *
763 * @param addr Address to check against
764 *
765 * @return If the address in question is in range
766 */
767 bool inRange(Addr addr) const;
768
769 /**
770 * Find next request ready time from among possible sources.
771 */
772 Tick nextQueueReadyTime() const;
773
774 /** Block size of this cache */
775 const unsigned blkSize;
776
777 /**
778 * The latency of tag lookup of a cache. It occurs when there is
779 * an access to the cache.
780 */
781 const Cycles lookupLatency;
782
783 /**
784 * The latency of data access of a cache. It occurs when there is
785 * an access to the cache.
786 */
787 const Cycles dataLatency;
788
789 /**
790 * This is the forward latency of the cache. It occurs when there
791 * is a cache miss and a request is forwarded downstream, in
792 * particular an outbound miss.
793 */
794 const Cycles forwardLatency;
795
796 /** The latency to fill a cache block */
797 const Cycles fillLatency;
798
799 /**
800 * The latency of sending reponse to its upper level cache/core on
801 * a linefill. The responseLatency parameter captures this
802 * latency.
803 */
804 const Cycles responseLatency;
805
806 /** The number of targets for each MSHR. */
807 const int numTarget;
808
809 /** Do we forward snoops from mem side port through to cpu side port? */
810 bool forwardSnoops;
811
812 /**
813 * Clusivity with respect to the upstream cache, determining if we
814 * fill into both this cache and the cache above on a miss. Note
815 * that we currently do not support strict clusivity policies.
816 */
817 const Enums::Clusivity clusivity;
818
819 /**
820 * Is this cache read only, for example the instruction cache, or
821 * table-walker cache. A cache that is read only should never see
822 * any writes, and should never get any dirty data (and hence
823 * never have to do any writebacks).
824 */
825 const bool isReadOnly;
826
827 /**
828 * Bit vector of the blocking reasons for the access path.
829 * @sa #BlockedCause
830 */
831 uint8_t blocked;
832
833 /** Increasing order number assigned to each incoming request. */
834 uint64_t order;
835
836 /** Stores time the cache blocked for statistics. */
837 Cycles blockedCycle;
838
839 /** Pointer to the MSHR that has no targets. */
840 MSHR *noTargetMSHR;
841
842 /** The number of misses to trigger an exit event. */
843 Counter missCount;
844
845 /**
846 * The address range to which the cache responds on the CPU side.
847 * Normally this is all possible memory addresses. */
848 const AddrRangeList addrRanges;
849
850 public:
851 /** System we are currently operating in. */
852 System *system;
853
854 // Statistics
855 /**
856 * @addtogroup CacheStatistics
857 * @{
858 */
859
860 /** Number of hits per thread for each type of command.
861 @sa Packet::Command */
862 Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
863 /** Number of hits for demand accesses. */
864 Stats::Formula demandHits;
865 /** Number of hit for all accesses. */
866 Stats::Formula overallHits;
867
868 /** Number of misses per thread for each type of command.
869 @sa Packet::Command */
870 Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
871 /** Number of misses for demand accesses. */
872 Stats::Formula demandMisses;
873 /** Number of misses for all accesses. */
874 Stats::Formula overallMisses;
875
876 /**
877 * Total number of cycles per thread/command spent waiting for a miss.
878 * Used to calculate the average miss latency.
879 */
880 Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
881 /** Total number of cycles spent waiting for demand misses. */
882 Stats::Formula demandMissLatency;
883 /** Total number of cycles spent waiting for all misses. */
884 Stats::Formula overallMissLatency;
885
886 /** The number of accesses per command and thread. */
887 Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
888 /** The number of demand accesses. */
889 Stats::Formula demandAccesses;
890 /** The number of overall accesses. */
891 Stats::Formula overallAccesses;
892
893 /** The miss rate per command and thread. */
894 Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
895 /** The miss rate of all demand accesses. */
896 Stats::Formula demandMissRate;
897 /** The miss rate for all accesses. */
898 Stats::Formula overallMissRate;
899
900 /** The average miss latency per command and thread. */
901 Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
902 /** The average miss latency for demand misses. */
903 Stats::Formula demandAvgMissLatency;
904 /** The average miss latency for all misses. */
905 Stats::Formula overallAvgMissLatency;
906
907 /** The total number of cycles blocked for each blocked cause. */
908 Stats::Vector blocked_cycles;
909 /** The number of times this cache blocked for each blocked cause. */
910 Stats::Vector blocked_causes;
911
912 /** The average number of cycles blocked for each blocked cause. */
913 Stats::Formula avg_blocked;
914
915 /** The number of times a HW-prefetched block is evicted w/o reference. */
916 Stats::Scalar unusedPrefetches;
917
918 /** Number of blocks written back per thread. */
919 Stats::Vector writebacks;
920
921 /** Number of misses that hit in the MSHRs per command and thread. */
922 Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
923 /** Demand misses that hit in the MSHRs. */
924 Stats::Formula demandMshrHits;
925 /** Total number of misses that hit in the MSHRs. */
926 Stats::Formula overallMshrHits;
927
928 /** Number of misses that miss in the MSHRs, per command and thread. */
929 Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
930 /** Demand misses that miss in the MSHRs. */
931 Stats::Formula demandMshrMisses;
932 /** Total number of misses that miss in the MSHRs. */
933 Stats::Formula overallMshrMisses;
934
935 /** Number of misses that miss in the MSHRs, per command and thread. */
936 Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
937 /** Total number of misses that miss in the MSHRs. */
938 Stats::Formula overallMshrUncacheable;
939
940 /** Total cycle latency of each MSHR miss, per command and thread. */
941 Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
942 /** Total cycle latency of demand MSHR misses. */
943 Stats::Formula demandMshrMissLatency;
944 /** Total cycle latency of overall MSHR misses. */
945 Stats::Formula overallMshrMissLatency;
946
947 /** Total cycle latency of each MSHR miss, per command and thread. */
948 Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
949 /** Total cycle latency of overall MSHR misses. */
950 Stats::Formula overallMshrUncacheableLatency;
951
952#if 0
953 /** The total number of MSHR accesses per command and thread. */
954 Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
955 /** The total number of demand MSHR accesses. */
956 Stats::Formula demandMshrAccesses;
957 /** The total number of MSHR accesses. */
958 Stats::Formula overallMshrAccesses;
959#endif
960
961 /** The miss rate in the MSHRs pre command and thread. */
962 Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
963 /** The demand miss rate in the MSHRs. */
964 Stats::Formula demandMshrMissRate;
965 /** The overall miss rate in the MSHRs. */
966 Stats::Formula overallMshrMissRate;
967
968 /** The average latency of an MSHR miss, per command and thread. */
969 Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
970 /** The average latency of a demand MSHR miss. */
971 Stats::Formula demandAvgMshrMissLatency;
972 /** The average overall latency of an MSHR miss. */
973 Stats::Formula overallAvgMshrMissLatency;
974
975 /** The average latency of an MSHR miss, per command and thread. */
976 Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
977 /** The average overall latency of an MSHR miss. */
978 Stats::Formula overallAvgMshrUncacheableLatency;
979
980 /** Number of replacements of valid blocks. */
981 Stats::Scalar replacements;
982
983 /**
984 * @}
985 */
986
987 /**
988 * Register stats for this object.
989 */
990 void regStats() override;
991
992 public:
993 BaseCache(const BaseCacheParams *p, unsigned blk_size);
994 ~BaseCache();
995
996 void init() override;
997
998 BaseMasterPort &getMasterPort(const std::string &if_name,
999 PortID idx = InvalidPortID) override;
1000 BaseSlavePort &getSlavePort(const std::string &if_name,
1001 PortID idx = InvalidPortID) override;
1002
1003 /**
1004 * Query block size of a cache.
1005 * @return The block size
1006 */
1007 unsigned
1008 getBlockSize() const
1009 {
1010 return blkSize;
1011 }
1012
1013 const AddrRangeList &getAddrRanges() const { return addrRanges; }
1014
1015 MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
1016 {
1017 MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
1018 pkt, time, order++,
1019 allocOnFill(pkt->cmd));
1020
1021 if (mshrQueue.isFull()) {
1022 setBlocked((BlockedCause)MSHRQueue_MSHRs);
1023 }
1024
1025 if (sched_send) {
1026 // schedule the send
1027 schedMemSideSendEvent(time);
1028 }
1029
1030 return mshr;
1031 }
1032
1033 void allocateWriteBuffer(PacketPtr pkt, Tick time)
1034 {
1035 // should only see writes or clean evicts here
1036 assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);
1037
1038 Addr blk_addr = pkt->getBlockAddr(blkSize);
1039
1040 WriteQueueEntry *wq_entry =
1041 writeBuffer.findMatch(blk_addr, pkt->isSecure());
1042 if (wq_entry && !wq_entry->inService) {
1043 DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
1044 }
1045
1046 writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);
1047
1048 if (writeBuffer.isFull()) {
1049 setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
1050 }
1051
1052 // schedule the send
1053 schedMemSideSendEvent(time);
1054 }
1055
1056 /**
1057 * Returns true if the cache is blocked for accesses.
1058 */
1059 bool isBlocked() const
1060 {
1061 return blocked != 0;
1062 }
1063
1064 /**
1065 * Marks the access path of the cache as blocked for the given cause. This
1066 * also sets the blocked flag in the slave interface.
1067 * @param cause The reason for the cache blocking.
1068 */
1069 void setBlocked(BlockedCause cause)
1070 {
1071 uint8_t flag = 1 << cause;
1072 if (blocked == 0) {
1073 blocked_causes[cause]++;
1074 blockedCycle = curCycle();
1075 cpuSidePort.setBlocked();
1076 }
1077 blocked |= flag;
1078 DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
1079 }
1080
1081 /**
1082 * Marks the cache as unblocked for the given cause. This also clears the
1083 * blocked flags in the appropriate interfaces.
1084 * @param cause The newly unblocked cause.
1085 * @warning Calling this function can cause a blocked request on the bus to
1086 * access the cache. The cache must be in a state to handle that request.
1087 */
1088 void clearBlocked(BlockedCause cause)
1089 {
1090 uint8_t flag = 1 << cause;
1091 blocked &= ~flag;
1092 DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
1093 if (blocked == 0) {
1094 blocked_cycles[cause] += curCycle() - blockedCycle;
1095 cpuSidePort.clearBlocked();
1096 }
1097 }
1098
1099 /**
1100 * Schedule a send event for the memory-side port. If already
1101 * scheduled, this may reschedule the event at an earlier
1102 * time. When the specified time is reached, the port is free to
1103 * send either a response, a request, or a prefetch request.
1104 *
1105 * @param time The time when to attempt sending a packet.
1106 */
1107 void schedMemSideSendEvent(Tick time)
1108 {
1109 memSidePort.schedSendEvent(time);
1110 }
1111
1112 bool inCache(Addr addr, bool is_secure) const {
1113 return tags->findBlock(addr, is_secure);
1114 }
1115
1116 bool inMissQueue(Addr addr, bool is_secure) const {
1117 return mshrQueue.findMatch(addr, is_secure);
1118 }
1119
1120 void incMissCount(PacketPtr pkt)
1121 {
1122 assert(pkt->req->masterId() < system->maxMasters());
1123 misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
1124 pkt->req->incAccessDepth();
1125 if (missCount) {
1126 --missCount;
1127 if (missCount == 0)
1128 exitSimLoop("A cache reached the maximum miss count");
1129 }
1130 }
1131 void incHitCount(PacketPtr pkt)
1132 {
1133 assert(pkt->req->masterId() < system->maxMasters());
1134 hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
1135
1136 }
1137
1138 /**
1139 * Cache block visitor that writes back dirty cache blocks using
1140 * functional writes.
1141 */
1142 void writebackVisitor(CacheBlk &blk);
1143
1144 /**
1145 * Cache block visitor that invalidates all blocks in the cache.
1146 *
1147 * @warn Dirty cache lines will not be written back to memory.
1148 */
1149 void invalidateVisitor(CacheBlk &blk);
1150
1151 /**
1152 * Take an MSHR, turn it into a suitable downstream packet, and
1153 * send it out. This construct allows a queue entry to choose a suitable
1154 * approach based on its type.
1155 *
1156 * @param mshr The MSHR to turn into a packet and send
1157 * @return True if the port is waiting for a retry
1158 */
1159 virtual bool sendMSHRQueuePacket(MSHR* mshr);
1160
1161 /**
1162 * Similar to sendMSHR, but for a write-queue entry
1163 * instead. Create the packet, and send it, and if successful also
1164 * mark the entry in service.
1165 *
1166 * @param wq_entry The write-queue entry to turn into a packet and send
1167 * @return True if the port is waiting for a retry
1168 */
1169 bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
1170
1171 /**
1172 * Serialize the state of the caches
1173 *
1174 * We currently don't support checkpointing cache state, so this panics.
1175 */
1176 void serialize(CheckpointOut &cp) const override;
1177 void unserialize(CheckpointIn &cp) override;
1178
1179};
1180
1181/**
1182 * The write allocator inspects write packets and detects streaming
1183 * patterns. The write allocator supports a single stream where writes
1184 * are expected to access consecutive locations and keeps track of
1185 * size of the area covered by the concecutive writes in byteCount.
1186 *
1187 * 1) When byteCount has surpassed the coallesceLimit the mode
1188 * switches from ALLOCATE to COALESCE where writes should be delayed
1189 * until the whole block is written at which point a single packet
1190 * (whole line write) can service them.
1191 *
1192 * 2) When byteCount has also exceeded the noAllocateLimit (whole
1193 * line) we switch to NO_ALLOCATE when writes should not allocate in
1194 * the cache but rather send a whole line write to the memory below.
1195 */
1196class WriteAllocator : public SimObject {
1197 public:
1198 WriteAllocator(const WriteAllocatorParams *p) :
1199 SimObject(p),
1200 coalesceLimit(p->coalesce_limit * p->block_size),
1201 noAllocateLimit(p->no_allocate_limit * p->block_size),
1202 delayThreshold(p->delay_threshold)
1203 {
1204 reset();
1205 }
1206
1207 /**
1208 * Should writes be coalesced? This is true if the mode is set to
1209 * NO_ALLOCATE.
1210 *
1211 * @return return true if the cache should coalesce writes.
1212 */
1213 bool coalesce() const {
1214 return mode != WriteMode::ALLOCATE;
1215 }
1216
1217 /**
1218 * Should writes allocate?
1219 *
1220 * @return return true if the cache should not allocate for writes.
1221 */
1222 bool allocate() const {
1223 return mode != WriteMode::NO_ALLOCATE;
1224 }
1225
1226 /**
1227 * Reset the write allocator state, meaning that it allocates for
1228 * writes and has not recorded any information about qualifying
1229 * writes that might trigger a switch to coalescing and later no
1230 * allocation.
1231 */
1232 void reset() {
1233 mode = WriteMode::ALLOCATE;
1234 byteCount = 0;
1235 nextAddr = 0;
1236 }
1237
1238 /**
1239 * Access whether we need to delay the current write.
1240 *
1241 * @param blk_addr The block address the packet writes to
1242 * @return true if the current packet should be delayed
1243 */
1244 bool delay(Addr blk_addr) {
1245 if (delayCtr[blk_addr] > 0) {
1246 --delayCtr[blk_addr];
1247 return true;
1248 } else {
1249 return false;
1250 }
1251 }
1252
1253 /**
1254 * Clear delay counter for the input block
1255 *
1256 * @param blk_addr The accessed cache block
1257 */
1258 void resetDelay(Addr blk_addr) {
1259 delayCtr.erase(blk_addr);
1260 }
1261
1262 /**
1263 * Update the write mode based on the current write
1264 * packet. This method compares the packet's address with any
1265 * current stream, and updates the tracking and the mode
1266 * accordingly.
1267 *
1268 * @param write_addr Start address of the write request
1269 * @param write_size Size of the write request
1270 * @param blk_addr The block address that this packet writes to
1271 */
1272 void updateMode(Addr write_addr, unsigned write_size, Addr blk_addr);
1273
1274 private:
1275 /**
1276 * The current mode for write coalescing and allocation, either
1277 * normal operation (ALLOCATE), write coalescing (COALESCE), or
1278 * write coalescing without allocation (NO_ALLOCATE).
1279 */
1280 enum class WriteMode : char {
1281 ALLOCATE,
1282 COALESCE,
1283 NO_ALLOCATE,
1284 };
1285 WriteMode mode;
1286
1287 /** Address to match writes against to detect streams. */
1288 Addr nextAddr;
1289
1290 /**
1291 * Bytes written contiguously. Saturating once we no longer
1292 * allocate.
1293 */
1294 uint32_t byteCount;
1295
1296 /**
1297 * Limits for when to switch between the different write modes.
1298 */
1299 const uint32_t coalesceLimit;
1300 const uint32_t noAllocateLimit;
1301 /**
1302 * The number of times the allocator will delay an WriteReq MSHR.
1303 */
1304 const uint32_t delayThreshold;
1305
1306 /**
1307 * Keep track of the number of times the allocator has delayed an
1308 * WriteReq MSHR.
1309 */
1310 std::unordered_map<Addr, Counter> delayCtr;
1311};
1312
1313#endif //__MEM_CACHE_BASE_HH__
2 * Copyright (c) 2012-2013, 2015-2016, 2018 ARM Limited
3 * All rights reserved.
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2003-2005 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Erik Hallnor
41 * Steve Reinhardt
42 * Ron Dreslinski
43 * Andreas Hansson
44 * Nikos Nikoleris
45 */
46
47/**
48 * @file
49 * Declares a basic cache interface BaseCache.
50 */
51
52#ifndef __MEM_CACHE_BASE_HH__
53#define __MEM_CACHE_BASE_HH__
54
55#include <cassert>
56#include <cstdint>
57#include <string>
58
59#include "base/addr_range.hh"
60#include "base/statistics.hh"
61#include "base/trace.hh"
62#include "base/types.hh"
63#include "debug/Cache.hh"
64#include "debug/CachePort.hh"
65#include "enums/Clusivity.hh"
66#include "mem/cache/cache_blk.hh"
67#include "mem/cache/mshr_queue.hh"
68#include "mem/cache/tags/base.hh"
69#include "mem/cache/write_queue.hh"
70#include "mem/cache/write_queue_entry.hh"
71#include "mem/mem_object.hh"
72#include "mem/packet.hh"
73#include "mem/packet_queue.hh"
74#include "mem/qport.hh"
75#include "mem/request.hh"
76#include "params/WriteAllocator.hh"
77#include "sim/eventq.hh"
78#include "sim/serialize.hh"
79#include "sim/sim_exit.hh"
80#include "sim/system.hh"
81
82class BaseMasterPort;
83class BasePrefetcher;
84class BaseSlavePort;
85class MSHR;
86class MasterPort;
87class QueueEntry;
88struct BaseCacheParams;
89
90/**
91 * A basic cache interface. Implements some common functions for speed.
92 */
93class BaseCache : public MemObject
94{
95 protected:
96 /**
97 * Indexes to enumerate the MSHR queues.
98 */
99 enum MSHRQueueIndex {
100 MSHRQueue_MSHRs,
101 MSHRQueue_WriteBuffer
102 };
103
104 public:
105 /**
106 * Reasons for caches to be blocked.
107 */
108 enum BlockedCause {
109 Blocked_NoMSHRs = MSHRQueue_MSHRs,
110 Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
111 Blocked_NoTargets,
112 NUM_BLOCKED_CAUSES
113 };
114
115 protected:
116
117 /**
118 * A cache master port is used for the memory-side port of the
119 * cache, and in addition to the basic timing port that only sends
120 * response packets through a transmit list, it also offers the
121 * ability to schedule and send request packets (requests &
122 * writebacks). The send event is scheduled through schedSendEvent,
123 * and the sendDeferredPacket of the timing port is modified to
124 * consider both the transmit list and the requests from the MSHR.
125 */
126 class CacheMasterPort : public QueuedMasterPort
127 {
128
129 public:
130
131 /**
132 * Schedule a send of a request packet (from the MSHR). Note
133 * that we could already have a retry outstanding.
134 */
135 void schedSendEvent(Tick time)
136 {
137 DPRINTF(CachePort, "Scheduling send event at %llu\n", time);
138 reqQueue.schedSendEvent(time);
139 }
140
141 protected:
142
143 CacheMasterPort(const std::string &_name, BaseCache *_cache,
144 ReqPacketQueue &_reqQueue,
145 SnoopRespPacketQueue &_snoopRespQueue) :
146 QueuedMasterPort(_name, _cache, _reqQueue, _snoopRespQueue)
147 { }
148
149 /**
150 * Memory-side port always snoops.
151 *
152 * @return always true
153 */
154 virtual bool isSnooping() const { return true; }
155 };
156
157 /**
158 * Override the default behaviour of sendDeferredPacket to enable
159 * the memory-side cache port to also send requests based on the
160 * current MSHR status. This queue has a pointer to our specific
161 * cache implementation and is used by the MemSidePort.
162 */
163 class CacheReqPacketQueue : public ReqPacketQueue
164 {
165
166 protected:
167
168 BaseCache &cache;
169 SnoopRespPacketQueue &snoopRespQueue;
170
171 public:
172
173 CacheReqPacketQueue(BaseCache &cache, MasterPort &port,
174 SnoopRespPacketQueue &snoop_resp_queue,
175 const std::string &label) :
176 ReqPacketQueue(cache, port, label), cache(cache),
177 snoopRespQueue(snoop_resp_queue) { }
178
179 /**
180 * Override the normal sendDeferredPacket and do not only
181 * consider the transmit list (used for responses), but also
182 * requests.
183 */
184 virtual void sendDeferredPacket();
185
186 /**
187 * Check if there is a conflicting snoop response about to be
188 * send out, and if so simply stall any requests, and schedule
189 * a send event at the same time as the next snoop response is
190 * being sent out.
191 */
192 bool checkConflictingSnoop(Addr addr)
193 {
194 if (snoopRespQueue.hasAddr(addr)) {
195 DPRINTF(CachePort, "Waiting for snoop response to be "
196 "sent\n");
197 Tick when = snoopRespQueue.deferredPacketReadyTime();
198 schedSendEvent(when);
199 return true;
200 }
201 return false;
202 }
203 };
204
205
206 /**
207 * The memory-side port extends the base cache master port with
208 * access functions for functional, atomic and timing snoops.
209 */
210 class MemSidePort : public CacheMasterPort
211 {
212 private:
213
214 /** The cache-specific queue. */
215 CacheReqPacketQueue _reqQueue;
216
217 SnoopRespPacketQueue _snoopRespQueue;
218
219 // a pointer to our specific cache implementation
220 BaseCache *cache;
221
222 protected:
223
224 virtual void recvTimingSnoopReq(PacketPtr pkt);
225
226 virtual bool recvTimingResp(PacketPtr pkt);
227
228 virtual Tick recvAtomicSnoop(PacketPtr pkt);
229
230 virtual void recvFunctionalSnoop(PacketPtr pkt);
231
232 public:
233
234 MemSidePort(const std::string &_name, BaseCache *_cache,
235 const std::string &_label);
236 };
237
238 /**
239 * A cache slave port is used for the CPU-side port of the cache,
240 * and it is basically a simple timing port that uses a transmit
241 * list for responses to the CPU (or connected master). In
242 * addition, it has the functionality to block the port for
243 * incoming requests. If blocked, the port will issue a retry once
244 * unblocked.
245 */
246 class CacheSlavePort : public QueuedSlavePort
247 {
248
249 public:
250
251 /** Do not accept any new requests. */
252 void setBlocked();
253
254 /** Return to normal operation and accept new requests. */
255 void clearBlocked();
256
257 bool isBlocked() const { return blocked; }
258
259 protected:
260
261 CacheSlavePort(const std::string &_name, BaseCache *_cache,
262 const std::string &_label);
263
264 /** A normal packet queue used to store responses. */
265 RespPacketQueue queue;
266
267 bool blocked;
268
269 bool mustSendRetry;
270
271 private:
272
273 void processSendRetry();
274
275 EventFunctionWrapper sendRetryEvent;
276
277 };
278
279 /**
280 * The CPU-side port extends the base cache slave port with access
281 * functions for functional, atomic and timing requests.
282 */
283 class CpuSidePort : public CacheSlavePort
284 {
285 private:
286
287 // a pointer to our specific cache implementation
288 BaseCache *cache;
289
290 protected:
291 virtual bool recvTimingSnoopResp(PacketPtr pkt) override;
292
293 virtual bool tryTiming(PacketPtr pkt) override;
294
295 virtual bool recvTimingReq(PacketPtr pkt) override;
296
297 virtual Tick recvAtomic(PacketPtr pkt) override;
298
299 virtual void recvFunctional(PacketPtr pkt) override;
300
301 virtual AddrRangeList getAddrRanges() const override;
302
303 public:
304
305 CpuSidePort(const std::string &_name, BaseCache *_cache,
306 const std::string &_label);
307
308 };
309
310 CpuSidePort cpuSidePort;
311 MemSidePort memSidePort;
312
313 protected:
314
315 /** Miss status registers */
316 MSHRQueue mshrQueue;
317
318 /** Write/writeback buffer */
319 WriteQueue writeBuffer;
320
321 /** Tag and data Storage */
322 BaseTags *tags;
323
324 /** Prefetcher */
325 BasePrefetcher *prefetcher;
326
327 /**
328 * Notify the prefetcher on every access, not just misses.
329 */
330 const bool prefetchOnAccess;
331
332 /**
333 * The writeAllocator drive optimizations for streaming writes.
334 * It first determines whether a WriteReq MSHR should be delayed,
335 * thus ensuring that we wait longer in cases when we are write
336 * coalescing and allowing all the bytes of the line to be written
337 * before the MSHR packet is sent downstream. This works in unison
338 * with the tracking in the MSHR to check if the entire line is
339 * written. The write mode also affects the behaviour on filling
340 * any whole-line writes. Normally the cache allocates the line
341 * when receiving the InvalidateResp, but after seeing enough
342 * consecutive lines we switch to using the tempBlock, and thus
343 * end up not allocating the line, and instead turning the
344 * whole-line write into a writeback straight away.
345 */
346 WriteAllocator * const writeAllocator;
347
348 /**
349 * Temporary cache block for occasional transitory use. We use
350 * the tempBlock to fill when allocation fails (e.g., when there
351 * is an outstanding request that accesses the victim block) or
352 * when we want to avoid allocation (e.g., exclusive caches)
353 */
354 TempCacheBlk *tempBlock;
355
356 /**
357 * Upstream caches need this packet until true is returned, so
358 * hold it for deletion until a subsequent call
359 */
360 std::unique_ptr<Packet> pendingDelete;
361
362 /**
363 * Mark a request as in service (sent downstream in the memory
364 * system), effectively making this MSHR the ordering point.
365 */
366 void markInService(MSHR *mshr, bool pending_modified_resp)
367 {
368 bool wasFull = mshrQueue.isFull();
369 mshrQueue.markInService(mshr, pending_modified_resp);
370
371 if (wasFull && !mshrQueue.isFull()) {
372 clearBlocked(Blocked_NoMSHRs);
373 }
374 }
375
376 void markInService(WriteQueueEntry *entry)
377 {
378 bool wasFull = writeBuffer.isFull();
379 writeBuffer.markInService(entry);
380
381 if (wasFull && !writeBuffer.isFull()) {
382 clearBlocked(Blocked_NoWBBuffers);
383 }
384 }
385
386 /**
387 * Determine whether we should allocate on a fill or not. If this
388 * cache is mostly inclusive with regards to the upstream cache(s)
389 * we always allocate (for any non-forwarded and cacheable
390 * requests). In the case of a mostly exclusive cache, we allocate
391 * on fill if the packet did not come from a cache, thus if we:
392 * are dealing with a whole-line write (the latter behaves much
393 * like a writeback), the original target packet came from a
394 * non-caching source, or if we are performing a prefetch or LLSC.
395 *
396 * @param cmd Command of the incoming requesting packet
397 * @return Whether we should allocate on the fill
398 */
399 inline bool allocOnFill(MemCmd cmd) const
400 {
401 return clusivity == Enums::mostly_incl ||
402 cmd == MemCmd::WriteLineReq ||
403 cmd == MemCmd::ReadReq ||
404 cmd == MemCmd::WriteReq ||
405 cmd.isPrefetch() ||
406 cmd.isLLSC();
407 }
408
409 /**
410 * Regenerate block address using tags.
411 * Block address regeneration depends on whether we're using a temporary
412 * block or not.
413 *
414 * @param blk The block to regenerate address.
415 * @return The block's address.
416 */
417 Addr regenerateBlkAddr(CacheBlk* blk);
418
419 /**
420 * Does all the processing necessary to perform the provided request.
421 * @param pkt The memory request to perform.
422 * @param blk The cache block to be updated.
423 * @param lat The latency of the access.
424 * @param writebacks List for any writebacks that need to be performed.
425 * @return Boolean indicating whether the request was satisfied.
426 */
427 virtual bool access(PacketPtr pkt, CacheBlk *&blk, Cycles &lat,
428 PacketList &writebacks);
429
430 /*
431 * Handle a timing request that hit in the cache
432 *
433 * @param ptk The request packet
434 * @param blk The referenced block
435 * @param request_time The tick at which the block lookup is compete
436 */
437 virtual void handleTimingReqHit(PacketPtr pkt, CacheBlk *blk,
438 Tick request_time);
439
440 /*
441 * Handle a timing request that missed in the cache
442 *
443 * Implementation specific handling for different cache
444 * implementations
445 *
446 * @param ptk The request packet
447 * @param blk The referenced block
448 * @param forward_time The tick at which we can process dependent requests
449 * @param request_time The tick at which the block lookup is compete
450 */
451 virtual void handleTimingReqMiss(PacketPtr pkt, CacheBlk *blk,
452 Tick forward_time,
453 Tick request_time) = 0;
454
455 /*
456 * Handle a timing request that missed in the cache
457 *
458 * Common functionality across different cache implementations
459 *
460 * @param ptk The request packet
461 * @param blk The referenced block
462 * @param mshr Any existing mshr for the referenced cache block
463 * @param forward_time The tick at which we can process dependent requests
464 * @param request_time The tick at which the block lookup is compete
465 */
466 void handleTimingReqMiss(PacketPtr pkt, MSHR *mshr, CacheBlk *blk,
467 Tick forward_time, Tick request_time);
468
469 /**
470 * Performs the access specified by the request.
471 * @param pkt The request to perform.
472 */
473 virtual void recvTimingReq(PacketPtr pkt);
474
475 /**
476 * Handling the special case of uncacheable write responses to
477 * make recvTimingResp less cluttered.
478 */
479 void handleUncacheableWriteResp(PacketPtr pkt);
480
481 /**
482 * Service non-deferred MSHR targets using the received response
483 *
484 * Iterates through the list of targets that can be serviced with
485 * the current response. Any writebacks that need to performed
486 * must be appended to the writebacks parameter.
487 *
488 * @param mshr The MSHR that corresponds to the reponse
489 * @param pkt The response packet
490 * @param blk The reference block
491 * @param writebacks List of writebacks that need to be performed
492 */
493 virtual void serviceMSHRTargets(MSHR *mshr, const PacketPtr pkt,
494 CacheBlk *blk, PacketList& writebacks) = 0;
495
496 /**
497 * Handles a response (cache line fill/write ack) from the bus.
498 * @param pkt The response packet
499 */
500 virtual void recvTimingResp(PacketPtr pkt);
501
502 /**
503 * Snoops bus transactions to maintain coherence.
504 * @param pkt The current bus transaction.
505 */
506 virtual void recvTimingSnoopReq(PacketPtr pkt) = 0;
507
508 /**
509 * Handle a snoop response.
510 * @param pkt Snoop response packet
511 */
512 virtual void recvTimingSnoopResp(PacketPtr pkt) = 0;
513
514 /**
515 * Handle a request in atomic mode that missed in this cache
516 *
517 * Creates a downstream request, sends it to the memory below and
518 * handles the response. As we are in atomic mode all operations
519 * are performed immediately.
520 *
521 * @param pkt The packet with the requests
522 * @param blk The referenced block
523 * @param writebacks A list with packets for any performed writebacks
524 * @return Cycles for handling the request
525 */
526 virtual Cycles handleAtomicReqMiss(PacketPtr pkt, CacheBlk *&blk,
527 PacketList &writebacks) = 0;
528
529 /**
530 * Performs the access specified by the request.
531 * @param pkt The request to perform.
532 * @return The number of ticks required for the access.
533 */
534 virtual Tick recvAtomic(PacketPtr pkt);
535
536 /**
537 * Snoop for the provided request in the cache and return the estimated
538 * time taken.
539 * @param pkt The memory request to snoop
540 * @return The number of ticks required for the snoop.
541 */
542 virtual Tick recvAtomicSnoop(PacketPtr pkt) = 0;
543
544 /**
545 * Performs the access specified by the request.
546 *
547 * @param pkt The request to perform.
548 * @param fromCpuSide from the CPU side port or the memory side port
549 */
550 virtual void functionalAccess(PacketPtr pkt, bool from_cpu_side);
551
552 /**
553 * Handle doing the Compare and Swap function for SPARC.
554 */
555 void cmpAndSwap(CacheBlk *blk, PacketPtr pkt);
556
557 /**
558 * Return the next queue entry to service, either a pending miss
559 * from the MSHR queue, a buffered write from the write buffer, or
560 * something from the prefetcher. This function is responsible
561 * for prioritizing among those sources on the fly.
562 */
563 QueueEntry* getNextQueueEntry();
564
565 /**
566 * Insert writebacks into the write buffer
567 */
568 virtual void doWritebacks(PacketList& writebacks, Tick forward_time) = 0;
569
570 /**
571 * Send writebacks down the memory hierarchy in atomic mode
572 */
573 virtual void doWritebacksAtomic(PacketList& writebacks) = 0;
574
575 /**
576 * Create an appropriate downstream bus request packet.
577 *
578 * Creates a new packet with the request to be send to the memory
579 * below, or nullptr if the current request in cpu_pkt should just
580 * be forwarded on.
581 *
582 * @param cpu_pkt The miss packet that needs to be satisfied.
583 * @param blk The referenced block, can be nullptr.
584 * @param needs_writable Indicates that the block must be writable
585 * even if the request in cpu_pkt doesn't indicate that.
586 * @param is_whole_line_write True if there are writes for the
587 * whole line
588 * @return A packet send to the memory below
589 */
590 virtual PacketPtr createMissPacket(PacketPtr cpu_pkt, CacheBlk *blk,
591 bool needs_writable,
592 bool is_whole_line_write) const = 0;
593
594 /**
595 * Determine if clean lines should be written back or not. In
596 * cases where a downstream cache is mostly inclusive we likely
597 * want it to act as a victim cache also for lines that have not
598 * been modified. Hence, we cannot simply drop the line (or send a
599 * clean evict), but rather need to send the actual data.
600 */
601 const bool writebackClean;
602
603 /**
604 * Writebacks from the tempBlock, resulting on the response path
605 * in atomic mode, must happen after the call to recvAtomic has
606 * finished (for the right ordering of the packets). We therefore
607 * need to hold on to the packets, and have a method and an event
608 * to send them.
609 */
610 PacketPtr tempBlockWriteback;
611
612 /**
613 * Send the outstanding tempBlock writeback. To be called after
614 * recvAtomic finishes in cases where the block we filled is in
615 * fact the tempBlock, and now needs to be written back.
616 */
617 void writebackTempBlockAtomic() {
618 assert(tempBlockWriteback != nullptr);
619 PacketList writebacks{tempBlockWriteback};
620 doWritebacksAtomic(writebacks);
621 tempBlockWriteback = nullptr;
622 }
623
624 /**
625 * An event to writeback the tempBlock after recvAtomic
626 * finishes. To avoid other calls to recvAtomic getting in
627 * between, we create this event with a higher priority.
628 */
629 EventFunctionWrapper writebackTempBlockAtomicEvent;
630
631 /**
632 * Perform any necessary updates to the block and perform any data
633 * exchange between the packet and the block. The flags of the
634 * packet are also set accordingly.
635 *
636 * @param pkt Request packet from upstream that hit a block
637 * @param blk Cache block that the packet hit
638 * @param deferred_response Whether this request originally missed
639 * @param pending_downgrade Whether the writable flag is to be removed
640 */
641 virtual void satisfyRequest(PacketPtr pkt, CacheBlk *blk,
642 bool deferred_response = false,
643 bool pending_downgrade = false);
644
645 /**
646 * Maintain the clusivity of this cache by potentially
647 * invalidating a block. This method works in conjunction with
648 * satisfyRequest, but is separate to allow us to handle all MSHR
649 * targets before potentially dropping a block.
650 *
651 * @param from_cache Whether we have dealt with a packet from a cache
652 * @param blk The block that should potentially be dropped
653 */
654 void maintainClusivity(bool from_cache, CacheBlk *blk);
655
656 /**
657 * Handle a fill operation caused by a received packet.
658 *
659 * Populates a cache block and handles all outstanding requests for the
660 * satisfied fill request. This version takes two memory requests. One
661 * contains the fill data, the other is an optional target to satisfy.
662 * Note that the reason we return a list of writebacks rather than
663 * inserting them directly in the write buffer is that this function
664 * is called by both atomic and timing-mode accesses, and in atomic
665 * mode we don't mess with the write buffer (we just perform the
666 * writebacks atomically once the original request is complete).
667 *
668 * @param pkt The memory request with the fill data.
669 * @param blk The cache block if it already exists.
670 * @param writebacks List for any writebacks that need to be performed.
671 * @param allocate Whether to allocate a block or use the temp block
672 * @return Pointer to the new cache block.
673 */
674 CacheBlk *handleFill(PacketPtr pkt, CacheBlk *blk,
675 PacketList &writebacks, bool allocate);
676
677 /**
678 * Allocate a new block and perform any necessary writebacks
679 *
680 * Find a victim block and if necessary prepare writebacks for any
681 * existing data. May return nullptr if there are no replaceable
682 * blocks. If a replaceable block is found, it inserts the new block in
683 * its place. The new block, however, is not set as valid yet.
684 *
685 * @param pkt Packet holding the address to update
686 * @param writebacks A list of writeback packets for the evicted blocks
687 * @return the allocated block
688 */
689 CacheBlk *allocateBlock(const PacketPtr pkt, PacketList &writebacks);
690 /**
691 * Evict a cache block.
692 *
693 * Performs a writeback if necesssary and invalidates the block
694 *
695 * @param blk Block to invalidate
696 * @return A packet with the writeback, can be nullptr
697 */
698 M5_NODISCARD virtual PacketPtr evictBlock(CacheBlk *blk) = 0;
699
700 /**
701 * Evict a cache block.
702 *
703 * Performs a writeback if necesssary and invalidates the block
704 *
705 * @param blk Block to invalidate
706 * @param writebacks Return a list of packets with writebacks
707 */
708 virtual void evictBlock(CacheBlk *blk, PacketList &writebacks) = 0;
709
710 /**
711 * Invalidate a cache block.
712 *
713 * @param blk Block to invalidate
714 */
715 void invalidateBlock(CacheBlk *blk);
716
717 /**
718 * Create a writeback request for the given block.
719 *
720 * @param blk The block to writeback.
721 * @return The writeback request for the block.
722 */
723 PacketPtr writebackBlk(CacheBlk *blk);
724
725 /**
726 * Create a writeclean request for the given block.
727 *
728 * Creates a request that writes the block to the cache below
729 * without evicting the block from the current cache.
730 *
731 * @param blk The block to write clean.
732 * @param dest The destination of the write clean operation.
733 * @param id Use the given packet id for the write clean operation.
734 * @return The generated write clean packet.
735 */
736 PacketPtr writecleanBlk(CacheBlk *blk, Request::Flags dest, PacketId id);
737
738 /**
739 * Write back dirty blocks in the cache using functional accesses.
740 */
741 virtual void memWriteback() override;
742
743 /**
744 * Invalidates all blocks in the cache.
745 *
746 * @warn Dirty cache lines will not be written back to
747 * memory. Make sure to call functionalWriteback() first if you
748 * want the to write them to memory.
749 */
750 virtual void memInvalidate() override;
751
752 /**
753 * Determine if there are any dirty blocks in the cache.
754 *
755 * @return true if at least one block is dirty, false otherwise.
756 */
757 bool isDirty() const;
758
759 /**
760 * Determine if an address is in the ranges covered by this
761 * cache. This is useful to filter snoops.
762 *
763 * @param addr Address to check against
764 *
765 * @return If the address in question is in range
766 */
767 bool inRange(Addr addr) const;
768
769 /**
770 * Find next request ready time from among possible sources.
771 */
772 Tick nextQueueReadyTime() const;
773
774 /** Block size of this cache */
775 const unsigned blkSize;
776
777 /**
778 * The latency of tag lookup of a cache. It occurs when there is
779 * an access to the cache.
780 */
781 const Cycles lookupLatency;
782
783 /**
784 * The latency of data access of a cache. It occurs when there is
785 * an access to the cache.
786 */
787 const Cycles dataLatency;
788
789 /**
790 * This is the forward latency of the cache. It occurs when there
791 * is a cache miss and a request is forwarded downstream, in
792 * particular an outbound miss.
793 */
794 const Cycles forwardLatency;
795
796 /** The latency to fill a cache block */
797 const Cycles fillLatency;
798
799 /**
800 * The latency of sending reponse to its upper level cache/core on
801 * a linefill. The responseLatency parameter captures this
802 * latency.
803 */
804 const Cycles responseLatency;
805
806 /** The number of targets for each MSHR. */
807 const int numTarget;
808
809 /** Do we forward snoops from mem side port through to cpu side port? */
810 bool forwardSnoops;
811
812 /**
813 * Clusivity with respect to the upstream cache, determining if we
814 * fill into both this cache and the cache above on a miss. Note
815 * that we currently do not support strict clusivity policies.
816 */
817 const Enums::Clusivity clusivity;
818
819 /**
820 * Is this cache read only, for example the instruction cache, or
821 * table-walker cache. A cache that is read only should never see
822 * any writes, and should never get any dirty data (and hence
823 * never have to do any writebacks).
824 */
825 const bool isReadOnly;
826
827 /**
828 * Bit vector of the blocking reasons for the access path.
829 * @sa #BlockedCause
830 */
831 uint8_t blocked;
832
833 /** Increasing order number assigned to each incoming request. */
834 uint64_t order;
835
836 /** Stores time the cache blocked for statistics. */
837 Cycles blockedCycle;
838
839 /** Pointer to the MSHR that has no targets. */
840 MSHR *noTargetMSHR;
841
842 /** The number of misses to trigger an exit event. */
843 Counter missCount;
844
845 /**
846 * The address range to which the cache responds on the CPU side.
847 * Normally this is all possible memory addresses. */
848 const AddrRangeList addrRanges;
849
850 public:
851 /** System we are currently operating in. */
852 System *system;
853
854 // Statistics
855 /**
856 * @addtogroup CacheStatistics
857 * @{
858 */
859
860 /** Number of hits per thread for each type of command.
861 @sa Packet::Command */
862 Stats::Vector hits[MemCmd::NUM_MEM_CMDS];
863 /** Number of hits for demand accesses. */
864 Stats::Formula demandHits;
865 /** Number of hit for all accesses. */
866 Stats::Formula overallHits;
867
868 /** Number of misses per thread for each type of command.
869 @sa Packet::Command */
870 Stats::Vector misses[MemCmd::NUM_MEM_CMDS];
871 /** Number of misses for demand accesses. */
872 Stats::Formula demandMisses;
873 /** Number of misses for all accesses. */
874 Stats::Formula overallMisses;
875
876 /**
877 * Total number of cycles per thread/command spent waiting for a miss.
878 * Used to calculate the average miss latency.
879 */
880 Stats::Vector missLatency[MemCmd::NUM_MEM_CMDS];
881 /** Total number of cycles spent waiting for demand misses. */
882 Stats::Formula demandMissLatency;
883 /** Total number of cycles spent waiting for all misses. */
884 Stats::Formula overallMissLatency;
885
886 /** The number of accesses per command and thread. */
887 Stats::Formula accesses[MemCmd::NUM_MEM_CMDS];
888 /** The number of demand accesses. */
889 Stats::Formula demandAccesses;
890 /** The number of overall accesses. */
891 Stats::Formula overallAccesses;
892
893 /** The miss rate per command and thread. */
894 Stats::Formula missRate[MemCmd::NUM_MEM_CMDS];
895 /** The miss rate of all demand accesses. */
896 Stats::Formula demandMissRate;
897 /** The miss rate for all accesses. */
898 Stats::Formula overallMissRate;
899
900 /** The average miss latency per command and thread. */
901 Stats::Formula avgMissLatency[MemCmd::NUM_MEM_CMDS];
902 /** The average miss latency for demand misses. */
903 Stats::Formula demandAvgMissLatency;
904 /** The average miss latency for all misses. */
905 Stats::Formula overallAvgMissLatency;
906
907 /** The total number of cycles blocked for each blocked cause. */
908 Stats::Vector blocked_cycles;
909 /** The number of times this cache blocked for each blocked cause. */
910 Stats::Vector blocked_causes;
911
912 /** The average number of cycles blocked for each blocked cause. */
913 Stats::Formula avg_blocked;
914
915 /** The number of times a HW-prefetched block is evicted w/o reference. */
916 Stats::Scalar unusedPrefetches;
917
918 /** Number of blocks written back per thread. */
919 Stats::Vector writebacks;
920
921 /** Number of misses that hit in the MSHRs per command and thread. */
922 Stats::Vector mshr_hits[MemCmd::NUM_MEM_CMDS];
923 /** Demand misses that hit in the MSHRs. */
924 Stats::Formula demandMshrHits;
925 /** Total number of misses that hit in the MSHRs. */
926 Stats::Formula overallMshrHits;
927
928 /** Number of misses that miss in the MSHRs, per command and thread. */
929 Stats::Vector mshr_misses[MemCmd::NUM_MEM_CMDS];
930 /** Demand misses that miss in the MSHRs. */
931 Stats::Formula demandMshrMisses;
932 /** Total number of misses that miss in the MSHRs. */
933 Stats::Formula overallMshrMisses;
934
935 /** Number of misses that miss in the MSHRs, per command and thread. */
936 Stats::Vector mshr_uncacheable[MemCmd::NUM_MEM_CMDS];
937 /** Total number of misses that miss in the MSHRs. */
938 Stats::Formula overallMshrUncacheable;
939
940 /** Total cycle latency of each MSHR miss, per command and thread. */
941 Stats::Vector mshr_miss_latency[MemCmd::NUM_MEM_CMDS];
942 /** Total cycle latency of demand MSHR misses. */
943 Stats::Formula demandMshrMissLatency;
944 /** Total cycle latency of overall MSHR misses. */
945 Stats::Formula overallMshrMissLatency;
946
947 /** Total cycle latency of each MSHR miss, per command and thread. */
948 Stats::Vector mshr_uncacheable_lat[MemCmd::NUM_MEM_CMDS];
949 /** Total cycle latency of overall MSHR misses. */
950 Stats::Formula overallMshrUncacheableLatency;
951
952#if 0
953 /** The total number of MSHR accesses per command and thread. */
954 Stats::Formula mshrAccesses[MemCmd::NUM_MEM_CMDS];
955 /** The total number of demand MSHR accesses. */
956 Stats::Formula demandMshrAccesses;
957 /** The total number of MSHR accesses. */
958 Stats::Formula overallMshrAccesses;
959#endif
960
961 /** The miss rate in the MSHRs pre command and thread. */
962 Stats::Formula mshrMissRate[MemCmd::NUM_MEM_CMDS];
963 /** The demand miss rate in the MSHRs. */
964 Stats::Formula demandMshrMissRate;
965 /** The overall miss rate in the MSHRs. */
966 Stats::Formula overallMshrMissRate;
967
968 /** The average latency of an MSHR miss, per command and thread. */
969 Stats::Formula avgMshrMissLatency[MemCmd::NUM_MEM_CMDS];
970 /** The average latency of a demand MSHR miss. */
971 Stats::Formula demandAvgMshrMissLatency;
972 /** The average overall latency of an MSHR miss. */
973 Stats::Formula overallAvgMshrMissLatency;
974
975 /** The average latency of an MSHR miss, per command and thread. */
976 Stats::Formula avgMshrUncacheableLatency[MemCmd::NUM_MEM_CMDS];
977 /** The average overall latency of an MSHR miss. */
978 Stats::Formula overallAvgMshrUncacheableLatency;
979
980 /** Number of replacements of valid blocks. */
981 Stats::Scalar replacements;
982
983 /**
984 * @}
985 */
986
987 /**
988 * Register stats for this object.
989 */
990 void regStats() override;
991
992 public:
993 BaseCache(const BaseCacheParams *p, unsigned blk_size);
994 ~BaseCache();
995
996 void init() override;
997
998 BaseMasterPort &getMasterPort(const std::string &if_name,
999 PortID idx = InvalidPortID) override;
1000 BaseSlavePort &getSlavePort(const std::string &if_name,
1001 PortID idx = InvalidPortID) override;
1002
1003 /**
1004 * Query block size of a cache.
1005 * @return The block size
1006 */
1007 unsigned
1008 getBlockSize() const
1009 {
1010 return blkSize;
1011 }
1012
1013 const AddrRangeList &getAddrRanges() const { return addrRanges; }
1014
1015 MSHR *allocateMissBuffer(PacketPtr pkt, Tick time, bool sched_send = true)
1016 {
1017 MSHR *mshr = mshrQueue.allocate(pkt->getBlockAddr(blkSize), blkSize,
1018 pkt, time, order++,
1019 allocOnFill(pkt->cmd));
1020
1021 if (mshrQueue.isFull()) {
1022 setBlocked((BlockedCause)MSHRQueue_MSHRs);
1023 }
1024
1025 if (sched_send) {
1026 // schedule the send
1027 schedMemSideSendEvent(time);
1028 }
1029
1030 return mshr;
1031 }
1032
1033 void allocateWriteBuffer(PacketPtr pkt, Tick time)
1034 {
1035 // should only see writes or clean evicts here
1036 assert(pkt->isWrite() || pkt->cmd == MemCmd::CleanEvict);
1037
1038 Addr blk_addr = pkt->getBlockAddr(blkSize);
1039
1040 WriteQueueEntry *wq_entry =
1041 writeBuffer.findMatch(blk_addr, pkt->isSecure());
1042 if (wq_entry && !wq_entry->inService) {
1043 DPRINTF(Cache, "Potential to merge writeback %s", pkt->print());
1044 }
1045
1046 writeBuffer.allocate(blk_addr, blkSize, pkt, time, order++);
1047
1048 if (writeBuffer.isFull()) {
1049 setBlocked((BlockedCause)MSHRQueue_WriteBuffer);
1050 }
1051
1052 // schedule the send
1053 schedMemSideSendEvent(time);
1054 }
1055
1056 /**
1057 * Returns true if the cache is blocked for accesses.
1058 */
1059 bool isBlocked() const
1060 {
1061 return blocked != 0;
1062 }
1063
1064 /**
1065 * Marks the access path of the cache as blocked for the given cause. This
1066 * also sets the blocked flag in the slave interface.
1067 * @param cause The reason for the cache blocking.
1068 */
1069 void setBlocked(BlockedCause cause)
1070 {
1071 uint8_t flag = 1 << cause;
1072 if (blocked == 0) {
1073 blocked_causes[cause]++;
1074 blockedCycle = curCycle();
1075 cpuSidePort.setBlocked();
1076 }
1077 blocked |= flag;
1078 DPRINTF(Cache,"Blocking for cause %d, mask=%d\n", cause, blocked);
1079 }
1080
1081 /**
1082 * Marks the cache as unblocked for the given cause. This also clears the
1083 * blocked flags in the appropriate interfaces.
1084 * @param cause The newly unblocked cause.
1085 * @warning Calling this function can cause a blocked request on the bus to
1086 * access the cache. The cache must be in a state to handle that request.
1087 */
1088 void clearBlocked(BlockedCause cause)
1089 {
1090 uint8_t flag = 1 << cause;
1091 blocked &= ~flag;
1092 DPRINTF(Cache,"Unblocking for cause %d, mask=%d\n", cause, blocked);
1093 if (blocked == 0) {
1094 blocked_cycles[cause] += curCycle() - blockedCycle;
1095 cpuSidePort.clearBlocked();
1096 }
1097 }
1098
1099 /**
1100 * Schedule a send event for the memory-side port. If already
1101 * scheduled, this may reschedule the event at an earlier
1102 * time. When the specified time is reached, the port is free to
1103 * send either a response, a request, or a prefetch request.
1104 *
1105 * @param time The time when to attempt sending a packet.
1106 */
1107 void schedMemSideSendEvent(Tick time)
1108 {
1109 memSidePort.schedSendEvent(time);
1110 }
1111
1112 bool inCache(Addr addr, bool is_secure) const {
1113 return tags->findBlock(addr, is_secure);
1114 }
1115
1116 bool inMissQueue(Addr addr, bool is_secure) const {
1117 return mshrQueue.findMatch(addr, is_secure);
1118 }
1119
1120 void incMissCount(PacketPtr pkt)
1121 {
1122 assert(pkt->req->masterId() < system->maxMasters());
1123 misses[pkt->cmdToIndex()][pkt->req->masterId()]++;
1124 pkt->req->incAccessDepth();
1125 if (missCount) {
1126 --missCount;
1127 if (missCount == 0)
1128 exitSimLoop("A cache reached the maximum miss count");
1129 }
1130 }
1131 void incHitCount(PacketPtr pkt)
1132 {
1133 assert(pkt->req->masterId() < system->maxMasters());
1134 hits[pkt->cmdToIndex()][pkt->req->masterId()]++;
1135
1136 }
1137
1138 /**
1139 * Cache block visitor that writes back dirty cache blocks using
1140 * functional writes.
1141 */
1142 void writebackVisitor(CacheBlk &blk);
1143
1144 /**
1145 * Cache block visitor that invalidates all blocks in the cache.
1146 *
1147 * @warn Dirty cache lines will not be written back to memory.
1148 */
1149 void invalidateVisitor(CacheBlk &blk);
1150
1151 /**
1152 * Take an MSHR, turn it into a suitable downstream packet, and
1153 * send it out. This construct allows a queue entry to choose a suitable
1154 * approach based on its type.
1155 *
1156 * @param mshr The MSHR to turn into a packet and send
1157 * @return True if the port is waiting for a retry
1158 */
1159 virtual bool sendMSHRQueuePacket(MSHR* mshr);
1160
1161 /**
1162 * Similar to sendMSHR, but for a write-queue entry
1163 * instead. Create the packet, and send it, and if successful also
1164 * mark the entry in service.
1165 *
1166 * @param wq_entry The write-queue entry to turn into a packet and send
1167 * @return True if the port is waiting for a retry
1168 */
1169 bool sendWriteQueuePacket(WriteQueueEntry* wq_entry);
1170
1171 /**
1172 * Serialize the state of the caches
1173 *
1174 * We currently don't support checkpointing cache state, so this panics.
1175 */
1176 void serialize(CheckpointOut &cp) const override;
1177 void unserialize(CheckpointIn &cp) override;
1178
1179};
1180
1181/**
1182 * The write allocator inspects write packets and detects streaming
1183 * patterns. The write allocator supports a single stream where writes
1184 * are expected to access consecutive locations and keeps track of
1185 * size of the area covered by the concecutive writes in byteCount.
1186 *
1187 * 1) When byteCount has surpassed the coallesceLimit the mode
1188 * switches from ALLOCATE to COALESCE where writes should be delayed
1189 * until the whole block is written at which point a single packet
1190 * (whole line write) can service them.
1191 *
1192 * 2) When byteCount has also exceeded the noAllocateLimit (whole
1193 * line) we switch to NO_ALLOCATE when writes should not allocate in
1194 * the cache but rather send a whole line write to the memory below.
1195 */
1196class WriteAllocator : public SimObject {
1197 public:
1198 WriteAllocator(const WriteAllocatorParams *p) :
1199 SimObject(p),
1200 coalesceLimit(p->coalesce_limit * p->block_size),
1201 noAllocateLimit(p->no_allocate_limit * p->block_size),
1202 delayThreshold(p->delay_threshold)
1203 {
1204 reset();
1205 }
1206
1207 /**
1208 * Should writes be coalesced? This is true if the mode is set to
1209 * NO_ALLOCATE.
1210 *
1211 * @return return true if the cache should coalesce writes.
1212 */
1213 bool coalesce() const {
1214 return mode != WriteMode::ALLOCATE;
1215 }
1216
1217 /**
1218 * Should writes allocate?
1219 *
1220 * @return return true if the cache should not allocate for writes.
1221 */
1222 bool allocate() const {
1223 return mode != WriteMode::NO_ALLOCATE;
1224 }
1225
1226 /**
1227 * Reset the write allocator state, meaning that it allocates for
1228 * writes and has not recorded any information about qualifying
1229 * writes that might trigger a switch to coalescing and later no
1230 * allocation.
1231 */
1232 void reset() {
1233 mode = WriteMode::ALLOCATE;
1234 byteCount = 0;
1235 nextAddr = 0;
1236 }
1237
1238 /**
1239 * Access whether we need to delay the current write.
1240 *
1241 * @param blk_addr The block address the packet writes to
1242 * @return true if the current packet should be delayed
1243 */
1244 bool delay(Addr blk_addr) {
1245 if (delayCtr[blk_addr] > 0) {
1246 --delayCtr[blk_addr];
1247 return true;
1248 } else {
1249 return false;
1250 }
1251 }
1252
1253 /**
1254 * Clear delay counter for the input block
1255 *
1256 * @param blk_addr The accessed cache block
1257 */
1258 void resetDelay(Addr blk_addr) {
1259 delayCtr.erase(blk_addr);
1260 }
1261
1262 /**
1263 * Update the write mode based on the current write
1264 * packet. This method compares the packet's address with any
1265 * current stream, and updates the tracking and the mode
1266 * accordingly.
1267 *
1268 * @param write_addr Start address of the write request
1269 * @param write_size Size of the write request
1270 * @param blk_addr The block address that this packet writes to
1271 */
1272 void updateMode(Addr write_addr, unsigned write_size, Addr blk_addr);
1273
1274 private:
1275 /**
1276 * The current mode for write coalescing and allocation, either
1277 * normal operation (ALLOCATE), write coalescing (COALESCE), or
1278 * write coalescing without allocation (NO_ALLOCATE).
1279 */
1280 enum class WriteMode : char {
1281 ALLOCATE,
1282 COALESCE,
1283 NO_ALLOCATE,
1284 };
1285 WriteMode mode;
1286
1287 /** Address to match writes against to detect streams. */
1288 Addr nextAddr;
1289
1290 /**
1291 * Bytes written contiguously. Saturating once we no longer
1292 * allocate.
1293 */
1294 uint32_t byteCount;
1295
1296 /**
1297 * Limits for when to switch between the different write modes.
1298 */
1299 const uint32_t coalesceLimit;
1300 const uint32_t noAllocateLimit;
1301 /**
1302 * The number of times the allocator will delay an WriteReq MSHR.
1303 */
1304 const uint32_t delayThreshold;
1305
1306 /**
1307 * Keep track of the number of times the allocator has delayed an
1308 * WriteReq MSHR.
1309 */
1310 std::unordered_map<Addr, Counter> delayCtr;
1311};
1312
1313#endif //__MEM_CACHE_BASE_HH__