mshr.cc revision 9725
1/* 2 * Copyright (c) 2012 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), 66 postDowngrade(false), queue(NULL), order(0), addr(0), size(0), 67 inService(false), isForward(false), threadNum(InvalidThreadID), 68 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, 205 Tick whenReady, Counter _order) 206{ 207 addr = _addr; 208 size = _size; 209 readyTime = whenReady; 210 order = _order; 211 assert(target); 212 isForward = false; 213 _isUncacheable = target->req->isUncacheable(); 214 inService = false; 215 downstreamPending = false; 216 threadNum = 0; 217 assert(targets.isReset()); 218 // Don't know of a case where we would allocate a new MSHR for a 219 // snoop (mem-side request), so set source according to request here 220 Target::Source source = (target->cmd == MemCmd::HardPFReq) ? 221 Target::FromPrefetcher : Target::FromCPU; 222 targets.add(target, whenReady, _order, source, true); 223 assert(deferredTargets.isReset()); 224 data = NULL; 225} 226 227 228void 229MSHR::clearDownstreamPending() 230{ 231 assert(downstreamPending); 232 downstreamPending = false; 233 // recursively clear flag on any MSHRs we will be forwarding 234 // responses to 235 targets.clearDownstreamPending(); 236} 237 238bool 239MSHR::markInService(PacketPtr pkt) 240{ 241 assert(!inService); 242 if (isForwardNoResponse()) { 243 // we just forwarded the request packet & don't expect a 244 // response, so get rid of it 245 assert(getNumTargets() == 1); 246 popTarget(); 247 return true; 248 } 249 inService = true; 250 pendingDirty = (targets.needsExclusive || 251 (!pkt->sharedAsserted() && pkt->memInhibitAsserted())); 252 postInvalidate = postDowngrade = false; 253 254 if (!downstreamPending) { 255 // let upstream caches know that the request has made it to a 256 // level where it's going to get a response 257 targets.clearDownstreamPending(); 258 } 259 return false; 260} 261 262 263void 264MSHR::deallocate() 265{ 266 assert(targets.empty()); 267 targets.resetFlags(); 268 assert(deferredTargets.isReset()); 269 inService = false; 270} 271 272/* 273 * Adds a target to an MSHR 274 */ 275void 276MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order) 277{ 278 // if there's a request already in service for this MSHR, we will 279 // have to defer the new target until after the response if any of 280 // the following are true: 281 // - there are other targets already deferred 282 // - there's a pending invalidate to be applied after the response 283 // comes back (but before this target is processed) 284 // - this target requires an exclusive block and either we're not 285 // getting an exclusive block back or we have already snooped 286 // another read request that will downgrade our exclusive block 287 // to shared 288 289 // assume we'd never issue a prefetch when we've got an 290 // outstanding miss 291 assert(pkt->cmd != MemCmd::HardPFReq); 292 293 if (inService && 294 (!deferredTargets.empty() || hasPostInvalidate() || 295 (pkt->needsExclusive() && 296 (!isPendingDirty() || hasPostDowngrade() || isForward)))) { 297 // need to put on deferred list 298 if (hasPostInvalidate()) 299 replaceUpgrade(pkt); 300 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true); 301 } else { 302 // No request outstanding, or still OK to append to 303 // outstanding request: append to regular target list. Only 304 // mark pending if current request hasn't been issued yet 305 // (isn't in service). 306 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService); 307 } 308} 309 310bool 311MSHR::handleSnoop(PacketPtr pkt, Counter _order) 312{ 313 DPRINTF(Cache, "%s for %s address %x size %d\n", __func__, 314 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 315 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { 316 // Request has not been issued yet, or it's been issued 317 // locally but is buffered unissued at some downstream cache 318 // which is forwarding us this snoop. Either way, the packet 319 // we're snooping logically precedes this MSHR's request, so 320 // the snoop has no impact on the MSHR, but must be processed 321 // in the standard way by the cache. The only exception is 322 // that if we're an L2+ cache buffering an UpgradeReq from a 323 // higher-level cache, and the snoop is invalidating, then our 324 // buffered upgrades must be converted to read exclusives, 325 // since the upper-level cache no longer has a valid copy. 326 // That is, even though the upper-level cache got out on its 327 // local bus first, some other invalidating transaction 328 // reached the global bus before the upgrade did. 329 if (pkt->needsExclusive()) { 330 targets.replaceUpgrades(); 331 deferredTargets.replaceUpgrades(); 332 } 333 334 return false; 335 } 336 337 // From here on down, the request issued by this MSHR logically 338 // precedes the request we're snooping. 339 if (pkt->needsExclusive()) { 340 // snooped request still precedes the re-request we'll have to 341 // issue for deferred targets, if any... 342 deferredTargets.replaceUpgrades(); 343 } 344 345 if (hasPostInvalidate()) { 346 // a prior snoop has already appended an invalidation, so 347 // logically we don't have the block anymore; no need for 348 // further snooping. 349 return true; 350 } 351 352 if (isPendingDirty() || pkt->isInvalidate()) { 353 // We need to save and replay the packet in two cases: 354 // 1. We're awaiting an exclusive copy, so ownership is pending, 355 // and we need to respond after we receive data. 356 // 2. It's an invalidation (e.g., UpgradeReq), and we need 357 // to forward the snoop up the hierarchy after the current 358 // transaction completes. 359 360 // Actual target device (typ. a memory) will delete the 361 // packet on reception, so we need to save a copy here. 362 PacketPtr cp_pkt = new Packet(pkt, true); 363 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, 364 downstreamPending && targets.needsExclusive); 365 366 if (isPendingDirty()) { 367 pkt->assertMemInhibit(); 368 pkt->setSupplyExclusive(); 369 } 370 371 if (pkt->needsExclusive()) { 372 // This transaction will take away our pending copy 373 postInvalidate = true; 374 } 375 } 376 377 if (!pkt->needsExclusive()) { 378 // This transaction will get a read-shared copy, downgrading 379 // our copy if we had an exclusive one 380 postDowngrade = true; 381 pkt->assertShared(); 382 } 383 384 return true; 385} 386 387 388bool 389MSHR::promoteDeferredTargets() 390{ 391 assert(targets.empty()); 392 if (deferredTargets.empty()) { 393 return false; 394 } 395 396 // swap targets & deferredTargets lists 397 std::swap(targets, deferredTargets); 398 399 // clear deferredTargets flags 400 deferredTargets.resetFlags(); 401 402 order = targets.front().order; 403 readyTime = std::max(curTick(), targets.front().readyTime); 404 405 return true; 406} 407 408 409void 410MSHR::handleFill(Packet *pkt, CacheBlk *blk) 411{ 412 if (!pkt->sharedAsserted() 413 && !(hasPostInvalidate() || hasPostDowngrade()) 414 && deferredTargets.needsExclusive) { 415 // We got an exclusive response, but we have deferred targets 416 // which are waiting to request an exclusive copy (not because 417 // of a pending invalidate). This can happen if the original 418 // request was for a read-only (non-exclusive) block, but we 419 // got an exclusive copy anyway because of the E part of the 420 // MOESI/MESI protocol. Since we got the exclusive copy 421 // there's no need to defer the targets, so move them up to 422 // the regular target list. 423 assert(!targets.needsExclusive); 424 targets.needsExclusive = true; 425 // if any of the deferred targets were upper-level cache 426 // requests marked downstreamPending, need to clear that 427 assert(!downstreamPending); // not pending here anymore 428 deferredTargets.clearDownstreamPending(); 429 // this clears out deferredTargets too 430 targets.splice(targets.end(), deferredTargets); 431 deferredTargets.resetFlags(); 432 } 433} 434 435 436bool 437MSHR::checkFunctional(PacketPtr pkt) 438{ 439 // For printing, we treat the MSHR as a whole as single entity. 440 // For other requests, we iterate over the individual targets 441 // since that's where the actual data lies. 442 if (pkt->isPrint()) { 443 pkt->checkFunctional(this, addr, size, NULL); 444 return false; 445 } else { 446 return (targets.checkFunctional(pkt) || 447 deferredTargets.checkFunctional(pkt)); 448 } 449} 450 451 452void 453MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const 454{ 455 ccprintf(os, "%s[%x:%x] %s %s %s state: %s %s %s %s %s\n", 456 prefix, addr, addr+size-1, 457 isForward ? "Forward" : "", 458 isForwardNoResponse() ? "ForwNoResp" : "", 459 needsExclusive() ? "Excl" : "", 460 _isUncacheable ? "Unc" : "", 461 inService ? "InSvc" : "", 462 downstreamPending ? "DwnPend" : "", 463 hasPostInvalidate() ? "PostInv" : "", 464 hasPostDowngrade() ? "PostDowngr" : ""); 465 466 ccprintf(os, "%s Targets:\n", prefix); 467 targets.print(os, verbosity, prefix + " "); 468 if (!deferredTargets.empty()) { 469 ccprintf(os, "%s Deferred Targets:\n", prefix); 470 deferredTargets.print(os, verbosity, prefix + " "); 471 } 472} 473 474std::string 475MSHR::print() const 476{ 477 ostringstream str; 478 print(str); 479 return str.str(); 480} 481