mshr.cc revision 10502
1/* 2 * Copyright (c) 2012-2013 ARM Limited 3 * All rights reserved. 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Copyright (c) 2002-2005 The Regents of The University of Michigan 15 * Copyright (c) 2010 Advanced Micro Devices, Inc. 16 * All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions are 20 * met: redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer; 22 * redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution; 25 * neither the name of the copyright holders nor the names of its 26 * contributors may be used to endorse or promote products derived from 27 * this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * Authors: Erik Hallnor 42 * Dave Greene 43 */ 44 45/** 46 * @file 47 * Miss Status and Handling Register (MSHR) definitions. 48 */ 49 50#include <algorithm> 51#include <cassert> 52#include <string> 53#include <vector> 54 55#include "base/misc.hh" 56#include "base/types.hh" 57#include "debug/Cache.hh" 58#include "mem/cache/cache.hh" 59#include "mem/cache/mshr.hh" 60#include "sim/core.hh" 61 62using namespace std; 63 64MSHR::MSHR() : readyTime(0), _isUncacheable(false), downstreamPending(false), 65 pendingDirty(false), postInvalidate(false), postDowngrade(false), 66 _isObsolete(false), queue(NULL), order(0), addr(0), size(0), 67 isSecure(false), inService(false), isForward(false), 68 threadNum(InvalidThreadID), data(NULL) 69{ 70} 71 72 73MSHR::TargetList::TargetList() 74 : needsExclusive(false), hasUpgrade(false) 75{} 76 77 78inline void 79MSHR::TargetList::add(PacketPtr pkt, Tick readyTime, 80 Counter order, Target::Source source, bool markPending) 81{ 82 if (source != Target::FromSnoop) { 83 if (pkt->needsExclusive()) { 84 needsExclusive = true; 85 } 86 87 // StoreCondReq is effectively an upgrade if it's in an MSHR 88 // since it would have been failed already if we didn't have a 89 // read-only copy 90 if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) { 91 hasUpgrade = true; 92 } 93 } 94 95 if (markPending) { 96 // Iterate over the SenderState stack and see if we find 97 // an MSHR entry. If we do, set the downstreamPending 98 // flag. Otherwise, do nothing. 99 MSHR *mshr = pkt->findNextSenderState<MSHR>(); 100 if (mshr != NULL) { 101 assert(!mshr->downstreamPending); 102 mshr->downstreamPending = true; 103 } 104 } 105 106 push_back(Target(pkt, readyTime, order, source, markPending)); 107} 108 109 110static void 111replaceUpgrade(PacketPtr pkt) 112{ 113 if (pkt->cmd == MemCmd::UpgradeReq) { 114 pkt->cmd = MemCmd::ReadExReq; 115 DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n"); 116 } else if (pkt->cmd == MemCmd::SCUpgradeReq) { 117 pkt->cmd = MemCmd::SCUpgradeFailReq; 118 DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n"); 119 } else if (pkt->cmd == MemCmd::StoreCondReq) { 120 pkt->cmd = MemCmd::StoreCondFailReq; 121 DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n"); 122 } 123} 124 125 126void 127MSHR::TargetList::replaceUpgrades() 128{ 129 if (!hasUpgrade) 130 return; 131 132 Iterator end_i = end(); 133 for (Iterator i = begin(); i != end_i; ++i) { 134 replaceUpgrade(i->pkt); 135 } 136 137 hasUpgrade = false; 138} 139 140 141void 142MSHR::TargetList::clearDownstreamPending() 143{ 144 Iterator end_i = end(); 145 for (Iterator i = begin(); i != end_i; ++i) { 146 if (i->markedPending) { 147 // Iterate over the SenderState stack and see if we find 148 // an MSHR entry. If we find one, clear the 149 // downstreamPending flag by calling 150 // clearDownstreamPending(). This recursively clears the 151 // downstreamPending flag in all caches this packet has 152 // passed through. 153 MSHR *mshr = i->pkt->findNextSenderState<MSHR>(); 154 if (mshr != NULL) { 155 mshr->clearDownstreamPending(); 156 } 157 } 158 } 159} 160 161 162bool 163MSHR::TargetList::checkFunctional(PacketPtr pkt) 164{ 165 Iterator end_i = end(); 166 for (Iterator i = begin(); i != end_i; ++i) { 167 if (pkt->checkFunctional(i->pkt)) { 168 return true; 169 } 170 } 171 172 return false; 173} 174 175 176void 177MSHR::TargetList:: 178print(std::ostream &os, int verbosity, const std::string &prefix) const 179{ 180 ConstIterator end_i = end(); 181 for (ConstIterator i = begin(); i != end_i; ++i) { 182 const char *s; 183 switch (i->source) { 184 case Target::FromCPU: 185 s = "FromCPU"; 186 break; 187 case Target::FromSnoop: 188 s = "FromSnoop"; 189 break; 190 case Target::FromPrefetcher: 191 s = "FromPrefetcher"; 192 break; 193 default: 194 s = ""; 195 break; 196 } 197 ccprintf(os, "%s%s: ", prefix, s); 198 i->pkt->print(os, verbosity, ""); 199 } 200} 201 202 203void 204MSHR::allocate(Addr _addr, int _size, PacketPtr target, Tick whenReady, 205 Counter _order) 206{ 207 addr = _addr; 208 size = _size; 209 isSecure = target->isSecure(); 210 readyTime = whenReady; 211 order = _order; 212 assert(target); 213 isForward = false; 214 _isUncacheable = target->req->isUncacheable(); 215 inService = false; 216 downstreamPending = false; 217 _isObsolete = false; 218 threadNum = 0; 219 assert(targets.isReset()); 220 // Don't know of a case where we would allocate a new MSHR for a 221 // snoop (mem-side request), so set source according to request here 222 Target::Source source = (target->cmd == MemCmd::HardPFReq) ? 223 Target::FromPrefetcher : Target::FromCPU; 224 targets.add(target, whenReady, _order, source, true); 225 assert(deferredTargets.isReset()); 226 data = NULL; 227} 228 229 230void 231MSHR::clearDownstreamPending() 232{ 233 assert(downstreamPending); 234 downstreamPending = false; 235 // recursively clear flag on any MSHRs we will be forwarding 236 // responses to 237 targets.clearDownstreamPending(); 238} 239 240bool 241MSHR::markInService(PacketPtr pkt) 242{ 243 assert(!inService); 244 if (isForwardNoResponse()) { 245 // we just forwarded the request packet & don't expect a 246 // response, so get rid of it 247 assert(getNumTargets() == 1); 248 popTarget(); 249 return true; 250 } 251 252 assert(pkt != NULL); 253 inService = true; 254 pendingDirty = (targets.needsExclusive || 255 (!pkt->sharedAsserted() && pkt->memInhibitAsserted())); 256 postInvalidate = postDowngrade = false; 257 258 if (!downstreamPending) { 259 // let upstream caches know that the request has made it to a 260 // level where it's going to get a response 261 targets.clearDownstreamPending(); 262 } 263 return false; 264} 265 266 267void 268MSHR::deallocate() 269{ 270 assert(targets.empty()); 271 targets.resetFlags(); 272 assert(deferredTargets.isReset()); 273 inService = false; 274} 275 276/* 277 * Adds a target to an MSHR 278 */ 279void 280MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order) 281{ 282 // if there's a request already in service for this MSHR, we will 283 // have to defer the new target until after the response if any of 284 // the following are true: 285 // - there are other targets already deferred 286 // - there's a pending invalidate to be applied after the response 287 // comes back (but before this target is processed) 288 // - this target requires an exclusive block and either we're not 289 // getting an exclusive block back or we have already snooped 290 // another read request that will downgrade our exclusive block 291 // to shared 292 293 // assume we'd never issue a prefetch when we've got an 294 // outstanding miss 295 assert(pkt->cmd != MemCmd::HardPFReq); 296 297 if (inService && 298 (!deferredTargets.empty() || hasPostInvalidate() || 299 (pkt->needsExclusive() && 300 (!isPendingDirty() || hasPostDowngrade() || isForward)))) { 301 // need to put on deferred list 302 if (hasPostInvalidate()) 303 replaceUpgrade(pkt); 304 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true); 305 } else { 306 // No request outstanding, or still OK to append to 307 // outstanding request: append to regular target list. Only 308 // mark pending if current request hasn't been issued yet 309 // (isn't in service). 310 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService); 311 } 312} 313 314bool 315MSHR::handleSnoop(PacketPtr pkt, Counter _order) 316{ 317 DPRINTF(Cache, "%s for %s address %x size %d\n", __func__, 318 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 319 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { 320 // Request has not been issued yet, or it's been issued 321 // locally but is buffered unissued at some downstream cache 322 // which is forwarding us this snoop. Either way, the packet 323 // we're snooping logically precedes this MSHR's request, so 324 // the snoop has no impact on the MSHR, but must be processed 325 // in the standard way by the cache. The only exception is 326 // that if we're an L2+ cache buffering an UpgradeReq from a 327 // higher-level cache, and the snoop is invalidating, then our 328 // buffered upgrades must be converted to read exclusives, 329 // since the upper-level cache no longer has a valid copy. 330 // That is, even though the upper-level cache got out on its 331 // local bus first, some other invalidating transaction 332 // reached the global bus before the upgrade did. 333 if (pkt->needsExclusive()) { 334 targets.replaceUpgrades(); 335 deferredTargets.replaceUpgrades(); 336 } 337 338 return false; 339 } 340 341 // From here on down, the request issued by this MSHR logically 342 // precedes the request we're snooping. 343 if (pkt->needsExclusive()) { 344 // snooped request still precedes the re-request we'll have to 345 // issue for deferred targets, if any... 346 deferredTargets.replaceUpgrades(); 347 } 348 349 if (hasPostInvalidate()) { 350 // a prior snoop has already appended an invalidation, so 351 // logically we don't have the block anymore; no need for 352 // further snooping. 353 return true; 354 } 355 356 if (isPendingDirty() || pkt->isInvalidate()) { 357 // We need to save and replay the packet in two cases: 358 // 1. We're awaiting an exclusive copy, so ownership is pending, 359 // and we need to respond after we receive data. 360 // 2. It's an invalidation (e.g., UpgradeReq), and we need 361 // to forward the snoop up the hierarchy after the current 362 // transaction completes. 363 364 // Actual target device (typ. a memory) will delete the 365 // packet on reception, so we need to save a copy here. 366 PacketPtr cp_pkt = new Packet(pkt, true); 367 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, 368 downstreamPending && targets.needsExclusive); 369 370 if (isPendingDirty()) { 371 pkt->assertMemInhibit(); 372 pkt->setSupplyExclusive(); 373 } 374 375 if (pkt->needsExclusive()) { 376 // This transaction will take away our pending copy 377 postInvalidate = true; 378 } 379 } 380 381 if (!pkt->needsExclusive()) { 382 // This transaction will get a read-shared copy, downgrading 383 // our copy if we had an exclusive one 384 postDowngrade = true; 385 pkt->assertShared(); 386 } 387 388 return true; 389} 390 391 392bool 393MSHR::promoteDeferredTargets() 394{ 395 assert(targets.empty()); 396 if (deferredTargets.empty()) { 397 return false; 398 } 399 400 // swap targets & deferredTargets lists 401 std::swap(targets, deferredTargets); 402 403 // clear deferredTargets flags 404 deferredTargets.resetFlags(); 405 406 order = targets.front().order; 407 readyTime = std::max(curTick(), targets.front().readyTime); 408 409 return true; 410} 411 412 413void 414MSHR::handleFill(Packet *pkt, CacheBlk *blk) 415{ 416 if (!pkt->sharedAsserted() 417 && !(hasPostInvalidate() || hasPostDowngrade()) 418 && deferredTargets.needsExclusive) { 419 // We got an exclusive response, but we have deferred targets 420 // which are waiting to request an exclusive copy (not because 421 // of a pending invalidate). This can happen if the original 422 // request was for a read-only (non-exclusive) block, but we 423 // got an exclusive copy anyway because of the E part of the 424 // MOESI/MESI protocol. Since we got the exclusive copy 425 // there's no need to defer the targets, so move them up to 426 // the regular target list. 427 assert(!targets.needsExclusive); 428 targets.needsExclusive = true; 429 // if any of the deferred targets were upper-level cache 430 // requests marked downstreamPending, need to clear that 431 assert(!downstreamPending); // not pending here anymore 432 deferredTargets.clearDownstreamPending(); 433 // this clears out deferredTargets too 434 targets.splice(targets.end(), deferredTargets); 435 deferredTargets.resetFlags(); 436 } 437} 438 439 440bool 441MSHR::checkFunctional(PacketPtr pkt) 442{ 443 // For printing, we treat the MSHR as a whole as single entity. 444 // For other requests, we iterate over the individual targets 445 // since that's where the actual data lies. 446 if (pkt->isPrint()) { 447 pkt->checkFunctional(this, addr, isSecure, size, NULL); 448 return false; 449 } else { 450 return (targets.checkFunctional(pkt) || 451 deferredTargets.checkFunctional(pkt)); 452 } 453} 454 455 456void 457MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const 458{ 459 ccprintf(os, "%s[%x:%x](%s) %s %s %s state: %s %s %s %s %s\n", 460 prefix, addr, addr+size-1, 461 isSecure ? "s" : "ns", 462 isForward ? "Forward" : "", 463 isForwardNoResponse() ? "ForwNoResp" : "", 464 needsExclusive() ? "Excl" : "", 465 _isUncacheable ? "Unc" : "", 466 inService ? "InSvc" : "", 467 downstreamPending ? "DwnPend" : "", 468 hasPostInvalidate() ? "PostInv" : "", 469 hasPostDowngrade() ? "PostDowngr" : ""); 470 471 ccprintf(os, "%s Targets:\n", prefix); 472 targets.print(os, verbosity, prefix + " "); 473 if (!deferredTargets.empty()) { 474 ccprintf(os, "%s Deferred Targets:\n", prefix); 475 deferredTargets.print(os, verbosity, prefix + " "); 476 } 477} 478 479std::string 480MSHR::print() const 481{ 482 ostringstream str; 483 print(str); 484 return str.str(); 485} 486