mshr.cc revision 10028
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), 66 postDowngrade(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 threadNum = 0; 218 assert(targets.isReset()); 219 // Don't know of a case where we would allocate a new MSHR for a 220 // snoop (mem-side request), so set source according to request here 221 Target::Source source = (target->cmd == MemCmd::HardPFReq) ? 222 Target::FromPrefetcher : Target::FromCPU; 223 targets.add(target, whenReady, _order, source, true); 224 assert(deferredTargets.isReset()); 225 data = NULL; 226} 227 228 229void 230MSHR::clearDownstreamPending() 231{ 232 assert(downstreamPending); 233 downstreamPending = false; 234 // recursively clear flag on any MSHRs we will be forwarding 235 // responses to 236 targets.clearDownstreamPending(); 237} 238 239bool 240MSHR::markInService(PacketPtr pkt) 241{ 242 assert(!inService); 243 if (isForwardNoResponse()) { 244 // we just forwarded the request packet & don't expect a 245 // response, so get rid of it 246 assert(getNumTargets() == 1); 247 popTarget(); 248 return true; 249 } 250 inService = true; 251 pendingDirty = (targets.needsExclusive || 252 (!pkt->sharedAsserted() && pkt->memInhibitAsserted())); 253 postInvalidate = postDowngrade = false; 254 255 if (!downstreamPending) { 256 // let upstream caches know that the request has made it to a 257 // level where it's going to get a response 258 targets.clearDownstreamPending(); 259 } 260 return false; 261} 262 263 264void 265MSHR::deallocate() 266{ 267 assert(targets.empty()); 268 targets.resetFlags(); 269 assert(deferredTargets.isReset()); 270 inService = false; 271} 272 273/* 274 * Adds a target to an MSHR 275 */ 276void 277MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order) 278{ 279 // if there's a request already in service for this MSHR, we will 280 // have to defer the new target until after the response if any of 281 // the following are true: 282 // - there are other targets already deferred 283 // - there's a pending invalidate to be applied after the response 284 // comes back (but before this target is processed) 285 // - this target requires an exclusive block and either we're not 286 // getting an exclusive block back or we have already snooped 287 // another read request that will downgrade our exclusive block 288 // to shared 289 290 // assume we'd never issue a prefetch when we've got an 291 // outstanding miss 292 assert(pkt->cmd != MemCmd::HardPFReq); 293 294 if (inService && 295 (!deferredTargets.empty() || hasPostInvalidate() || 296 (pkt->needsExclusive() && 297 (!isPendingDirty() || hasPostDowngrade() || isForward)))) { 298 // need to put on deferred list 299 if (hasPostInvalidate()) 300 replaceUpgrade(pkt); 301 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true); 302 } else { 303 // No request outstanding, or still OK to append to 304 // outstanding request: append to regular target list. Only 305 // mark pending if current request hasn't been issued yet 306 // (isn't in service). 307 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService); 308 } 309} 310 311bool 312MSHR::handleSnoop(PacketPtr pkt, Counter _order) 313{ 314 DPRINTF(Cache, "%s for %s address %x size %d\n", __func__, 315 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 316 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { 317 // Request has not been issued yet, or it's been issued 318 // locally but is buffered unissued at some downstream cache 319 // which is forwarding us this snoop. Either way, the packet 320 // we're snooping logically precedes this MSHR's request, so 321 // the snoop has no impact on the MSHR, but must be processed 322 // in the standard way by the cache. The only exception is 323 // that if we're an L2+ cache buffering an UpgradeReq from a 324 // higher-level cache, and the snoop is invalidating, then our 325 // buffered upgrades must be converted to read exclusives, 326 // since the upper-level cache no longer has a valid copy. 327 // That is, even though the upper-level cache got out on its 328 // local bus first, some other invalidating transaction 329 // reached the global bus before the upgrade did. 330 if (pkt->needsExclusive()) { 331 targets.replaceUpgrades(); 332 deferredTargets.replaceUpgrades(); 333 } 334 335 return false; 336 } 337 338 // From here on down, the request issued by this MSHR logically 339 // precedes the request we're snooping. 340 if (pkt->needsExclusive()) { 341 // snooped request still precedes the re-request we'll have to 342 // issue for deferred targets, if any... 343 deferredTargets.replaceUpgrades(); 344 } 345 346 if (hasPostInvalidate()) { 347 // a prior snoop has already appended an invalidation, so 348 // logically we don't have the block anymore; no need for 349 // further snooping. 350 return true; 351 } 352 353 if (isPendingDirty() || pkt->isInvalidate()) { 354 // We need to save and replay the packet in two cases: 355 // 1. We're awaiting an exclusive copy, so ownership is pending, 356 // and we need to respond after we receive data. 357 // 2. It's an invalidation (e.g., UpgradeReq), and we need 358 // to forward the snoop up the hierarchy after the current 359 // transaction completes. 360 361 // Actual target device (typ. a memory) will delete the 362 // packet on reception, so we need to save a copy here. 363 PacketPtr cp_pkt = new Packet(pkt, true); 364 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, 365 downstreamPending && targets.needsExclusive); 366 367 if (isPendingDirty()) { 368 pkt->assertMemInhibit(); 369 pkt->setSupplyExclusive(); 370 } 371 372 if (pkt->needsExclusive()) { 373 // This transaction will take away our pending copy 374 postInvalidate = true; 375 } 376 } 377 378 if (!pkt->needsExclusive()) { 379 // This transaction will get a read-shared copy, downgrading 380 // our copy if we had an exclusive one 381 postDowngrade = true; 382 pkt->assertShared(); 383 } 384 385 return true; 386} 387 388 389bool 390MSHR::promoteDeferredTargets() 391{ 392 assert(targets.empty()); 393 if (deferredTargets.empty()) { 394 return false; 395 } 396 397 // swap targets & deferredTargets lists 398 std::swap(targets, deferredTargets); 399 400 // clear deferredTargets flags 401 deferredTargets.resetFlags(); 402 403 order = targets.front().order; 404 readyTime = std::max(curTick(), targets.front().readyTime); 405 406 return true; 407} 408 409 410void 411MSHR::handleFill(Packet *pkt, CacheBlk *blk) 412{ 413 if (!pkt->sharedAsserted() 414 && !(hasPostInvalidate() || hasPostDowngrade()) 415 && deferredTargets.needsExclusive) { 416 // We got an exclusive response, but we have deferred targets 417 // which are waiting to request an exclusive copy (not because 418 // of a pending invalidate). This can happen if the original 419 // request was for a read-only (non-exclusive) block, but we 420 // got an exclusive copy anyway because of the E part of the 421 // MOESI/MESI protocol. Since we got the exclusive copy 422 // there's no need to defer the targets, so move them up to 423 // the regular target list. 424 assert(!targets.needsExclusive); 425 targets.needsExclusive = true; 426 // if any of the deferred targets were upper-level cache 427 // requests marked downstreamPending, need to clear that 428 assert(!downstreamPending); // not pending here anymore 429 deferredTargets.clearDownstreamPending(); 430 // this clears out deferredTargets too 431 targets.splice(targets.end(), deferredTargets); 432 deferredTargets.resetFlags(); 433 } 434} 435 436 437bool 438MSHR::checkFunctional(PacketPtr pkt) 439{ 440 // For printing, we treat the MSHR as a whole as single entity. 441 // For other requests, we iterate over the individual targets 442 // since that's where the actual data lies. 443 if (pkt->isPrint()) { 444 pkt->checkFunctional(this, addr, isSecure, size, NULL); 445 return false; 446 } else { 447 return (targets.checkFunctional(pkt) || 448 deferredTargets.checkFunctional(pkt)); 449 } 450} 451 452 453void 454MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const 455{ 456 ccprintf(os, "%s[%x:%x](%s) %s %s %s state: %s %s %s %s %s\n", 457 prefix, addr, addr+size-1, 458 isSecure ? "s" : "ns", 459 isForward ? "Forward" : "", 460 isForwardNoResponse() ? "ForwNoResp" : "", 461 needsExclusive() ? "Excl" : "", 462 _isUncacheable ? "Unc" : "", 463 inService ? "InSvc" : "", 464 downstreamPending ? "DwnPend" : "", 465 hasPostInvalidate() ? "PostInv" : "", 466 hasPostDowngrade() ? "PostDowngr" : ""); 467 468 ccprintf(os, "%s Targets:\n", prefix); 469 targets.print(os, verbosity, prefix + " "); 470 if (!deferredTargets.empty()) { 471 ccprintf(os, "%s Deferred Targets:\n", prefix); 472 deferredTargets.print(os, verbosity, prefix + " "); 473 } 474} 475 476std::string 477MSHR::print() const 478{ 479 ostringstream str; 480 print(str); 481 return str.str(); 482} 483