mshr.cc revision 11286
1/* 2 * Copyright (c) 2012-2013, 2015 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 pendingModified(false), 66 postInvalidate(false), postDowngrade(false), 67 queue(NULL), order(0), blkAddr(0), 68 blkSize(0), isSecure(false), inService(false), 69 isForward(false), allocOnFill(false), 70 data(NULL) 71{ 72} 73 74 75MSHR::TargetList::TargetList() 76 : needsWritable(false), hasUpgrade(false) 77{} 78 79 80inline void 81MSHR::TargetList::add(PacketPtr pkt, Tick readyTime, 82 Counter order, Target::Source source, bool markPending) 83{ 84 if (source != Target::FromSnoop) { 85 if (pkt->needsWritable()) { 86 needsWritable = true; 87 } 88 89 // StoreCondReq is effectively an upgrade if it's in an MSHR 90 // since it would have been failed already if we didn't have a 91 // read-only copy 92 if (pkt->isUpgrade() || pkt->cmd == MemCmd::StoreCondReq) { 93 hasUpgrade = true; 94 } 95 } 96 97 if (markPending) { 98 // Iterate over the SenderState stack and see if we find 99 // an MSHR entry. If we do, set the downstreamPending 100 // flag. Otherwise, do nothing. 101 MSHR *mshr = pkt->findNextSenderState<MSHR>(); 102 if (mshr != NULL) { 103 assert(!mshr->downstreamPending); 104 mshr->downstreamPending = true; 105 } else { 106 // No need to clear downstreamPending later 107 markPending = false; 108 } 109 } 110 111 emplace_back(pkt, readyTime, order, source, markPending); 112} 113 114 115static void 116replaceUpgrade(PacketPtr pkt) 117{ 118 // remember if the current packet has data allocated 119 bool has_data = pkt->hasData() || pkt->hasRespData(); 120 121 if (pkt->cmd == MemCmd::UpgradeReq) { 122 pkt->cmd = MemCmd::ReadExReq; 123 DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n"); 124 } else if (pkt->cmd == MemCmd::SCUpgradeReq) { 125 pkt->cmd = MemCmd::SCUpgradeFailReq; 126 DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n"); 127 } else if (pkt->cmd == MemCmd::StoreCondReq) { 128 pkt->cmd = MemCmd::StoreCondFailReq; 129 DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n"); 130 } 131 132 if (!has_data) { 133 // there is no sensible way of setting the data field if the 134 // new command actually would carry data 135 assert(!pkt->hasData()); 136 137 if (pkt->hasRespData()) { 138 // we went from a packet that had no data (neither request, 139 // nor response), to one that does, and therefore we need to 140 // actually allocate space for the data payload 141 pkt->allocate(); 142 } 143 } 144} 145 146 147void 148MSHR::TargetList::replaceUpgrades() 149{ 150 if (!hasUpgrade) 151 return; 152 153 for (auto& t : *this) { 154 replaceUpgrade(t.pkt); 155 } 156 157 hasUpgrade = false; 158} 159 160 161void 162MSHR::TargetList::clearDownstreamPending() 163{ 164 for (auto& t : *this) { 165 if (t.markedPending) { 166 // Iterate over the SenderState stack and see if we find 167 // an MSHR entry. If we find one, clear the 168 // downstreamPending flag by calling 169 // clearDownstreamPending(). This recursively clears the 170 // downstreamPending flag in all caches this packet has 171 // passed through. 172 MSHR *mshr = t.pkt->findNextSenderState<MSHR>(); 173 if (mshr != NULL) { 174 mshr->clearDownstreamPending(); 175 } 176 } 177 } 178} 179 180 181bool 182MSHR::TargetList::checkFunctional(PacketPtr pkt) 183{ 184 for (auto& t : *this) { 185 if (pkt->checkFunctional(t.pkt)) { 186 return true; 187 } 188 } 189 190 return false; 191} 192 193 194void 195MSHR::TargetList::print(std::ostream &os, int verbosity, 196 const std::string &prefix) const 197{ 198 for (auto& t : *this) { 199 const char *s; 200 switch (t.source) { 201 case Target::FromCPU: 202 s = "FromCPU"; 203 break; 204 case Target::FromSnoop: 205 s = "FromSnoop"; 206 break; 207 case Target::FromPrefetcher: 208 s = "FromPrefetcher"; 209 break; 210 default: 211 s = ""; 212 break; 213 } 214 ccprintf(os, "%s%s: ", prefix, s); 215 t.pkt->print(os, verbosity, ""); 216 } 217} 218 219 220void 221MSHR::allocate(Addr blk_addr, unsigned blk_size, PacketPtr target, 222 Tick when_ready, Counter _order, bool alloc_on_fill) 223{ 224 blkAddr = blk_addr; 225 blkSize = blk_size; 226 isSecure = target->isSecure(); 227 readyTime = when_ready; 228 order = _order; 229 assert(target); 230 isForward = false; 231 allocOnFill = alloc_on_fill; 232 _isUncacheable = target->req->isUncacheable(); 233 inService = false; 234 downstreamPending = false; 235 assert(targets.isReset()); 236 // Don't know of a case where we would allocate a new MSHR for a 237 // snoop (mem-side request), so set source according to request here 238 Target::Source source = (target->cmd == MemCmd::HardPFReq) ? 239 Target::FromPrefetcher : Target::FromCPU; 240 targets.add(target, when_ready, _order, source, true); 241 assert(deferredTargets.isReset()); 242 data = NULL; 243} 244 245 246void 247MSHR::clearDownstreamPending() 248{ 249 assert(downstreamPending); 250 downstreamPending = false; 251 // recursively clear flag on any MSHRs we will be forwarding 252 // responses to 253 targets.clearDownstreamPending(); 254} 255 256bool 257MSHR::markInService(bool pending_modified_resp) 258{ 259 assert(!inService); 260 if (isForwardNoResponse()) { 261 // we just forwarded the request packet & don't expect a 262 // response, so get rid of it 263 assert(getNumTargets() == 1); 264 popTarget(); 265 return true; 266 } 267 268 inService = true; 269 pendingModified = targets.needsWritable || pending_modified_resp; 270 postInvalidate = postDowngrade = false; 271 272 if (!downstreamPending) { 273 // let upstream caches know that the request has made it to a 274 // level where it's going to get a response 275 targets.clearDownstreamPending(); 276 } 277 return false; 278} 279 280 281void 282MSHR::deallocate() 283{ 284 assert(targets.empty()); 285 targets.resetFlags(); 286 assert(deferredTargets.isReset()); 287 inService = false; 288} 289 290/* 291 * Adds a target to an MSHR 292 */ 293void 294MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order, 295 bool alloc_on_fill) 296{ 297 // assume we'd never issue a prefetch when we've got an 298 // outstanding miss 299 assert(pkt->cmd != MemCmd::HardPFReq); 300 301 // uncacheable accesses always allocate a new MSHR, and cacheable 302 // accesses ignore any uncacheable MSHRs, thus we should never 303 // have targets addded if originally allocated uncacheable 304 assert(!_isUncacheable); 305 306 // potentially re-evaluate whether we should allocate on a fill or 307 // not 308 allocOnFill = allocOnFill || alloc_on_fill; 309 310 // if there's a request already in service for this MSHR, we will 311 // have to defer the new target until after the response if any of 312 // the following are true: 313 // - there are other targets already deferred 314 // - there's a pending invalidate to be applied after the response 315 // comes back (but before this target is processed) 316 // - this target requires a writable block and either we're not 317 // getting a writable block back or we have already snooped 318 // another read request that will downgrade our writable block 319 // to non-writable (Shared or Owned) 320 if (inService && 321 (!deferredTargets.empty() || hasPostInvalidate() || 322 (pkt->needsWritable() && 323 (!isPendingModified() || hasPostDowngrade() || isForward)))) { 324 // need to put on deferred list 325 if (hasPostInvalidate()) 326 replaceUpgrade(pkt); 327 deferredTargets.add(pkt, whenReady, _order, Target::FromCPU, true); 328 } else { 329 // No request outstanding, or still OK to append to 330 // outstanding request: append to regular target list. Only 331 // mark pending if current request hasn't been issued yet 332 // (isn't in service). 333 targets.add(pkt, whenReady, _order, Target::FromCPU, !inService); 334 } 335} 336 337bool 338MSHR::handleSnoop(PacketPtr pkt, Counter _order) 339{ 340 DPRINTF(Cache, "%s for %s addr %#llx size %d\n", __func__, 341 pkt->cmdString(), pkt->getAddr(), pkt->getSize()); 342 343 // when we snoop packets the needsWritable and isInvalidate flags 344 // should always be the same, however, this assumes that we never 345 // snoop writes as they are currently not marked as invalidations 346 panic_if(pkt->needsWritable() != pkt->isInvalidate(), 347 "%s got snoop %s to addr %#llx where needsWritable, " 348 "does not match isInvalidate", name(), pkt->cmdString(), 349 pkt->getAddr()); 350 351 if (!inService || (pkt->isExpressSnoop() && downstreamPending)) { 352 // Request has not been issued yet, or it's been issued 353 // locally but is buffered unissued at some downstream cache 354 // which is forwarding us this snoop. Either way, the packet 355 // we're snooping logically precedes this MSHR's request, so 356 // the snoop has no impact on the MSHR, but must be processed 357 // in the standard way by the cache. The only exception is 358 // that if we're an L2+ cache buffering an UpgradeReq from a 359 // higher-level cache, and the snoop is invalidating, then our 360 // buffered upgrades must be converted to read exclusives, 361 // since the upper-level cache no longer has a valid copy. 362 // That is, even though the upper-level cache got out on its 363 // local bus first, some other invalidating transaction 364 // reached the global bus before the upgrade did. 365 if (pkt->needsWritable()) { 366 targets.replaceUpgrades(); 367 deferredTargets.replaceUpgrades(); 368 } 369 370 return false; 371 } 372 373 // From here on down, the request issued by this MSHR logically 374 // precedes the request we're snooping. 375 if (pkt->needsWritable()) { 376 // snooped request still precedes the re-request we'll have to 377 // issue for deferred targets, if any... 378 deferredTargets.replaceUpgrades(); 379 } 380 381 if (hasPostInvalidate()) { 382 // a prior snoop has already appended an invalidation, so 383 // logically we don't have the block anymore; no need for 384 // further snooping. 385 return true; 386 } 387 388 if (isPendingModified() || pkt->isInvalidate()) { 389 // We need to save and replay the packet in two cases: 390 // 1. We're awaiting a writable copy (Modified or Exclusive), 391 // so this MSHR is the orgering point, and we need to respond 392 // after we receive data. 393 // 2. It's an invalidation (e.g., UpgradeReq), and we need 394 // to forward the snoop up the hierarchy after the current 395 // transaction completes. 396 397 // Start by determining if we will eventually respond or not, 398 // matching the conditions checked in Cache::handleSnoop 399 bool will_respond = isPendingModified() && pkt->needsResponse() && 400 pkt->cmd != MemCmd::InvalidateReq; 401 402 // The packet we are snooping may be deleted by the time we 403 // actually process the target, and we consequently need to 404 // save a copy here. Clear flags and also allocate new data as 405 // the original packet data storage may have been deleted by 406 // the time we get to process this packet. In the cases where 407 // we are not responding after handling the snoop we also need 408 // to create a copy of the request to be on the safe side. In 409 // the latter case the cache is responsible for deleting both 410 // the packet and the request as part of handling the deferred 411 // snoop. 412 PacketPtr cp_pkt = will_respond ? new Packet(pkt, true, true) : 413 new Packet(new Request(*pkt->req), pkt->cmd); 414 415 if (isPendingModified()) { 416 // we are the ordering point, and will consequently 417 // respond, and depending on whether the packet 418 // needsWritable or not we either pass a Shared line or a 419 // Modified line 420 pkt->setCacheResponding(); 421 422 // inform the cache hierarchy that this cache had the line 423 // in the Modified state, even if the response is passed 424 // as Shared (and thus non-writable) 425 pkt->setResponderHadWritable(); 426 427 // in the case of an uncacheable request there is no need 428 // to set the responderHadWritable flag, but since the 429 // recipient does not care there is no harm in doing so 430 } 431 targets.add(cp_pkt, curTick(), _order, Target::FromSnoop, 432 downstreamPending && targets.needsWritable); 433 434 if (pkt->needsWritable()) { 435 // This transaction will take away our pending copy 436 postInvalidate = true; 437 } 438 } 439 440 if (!pkt->needsWritable() && !pkt->req->isUncacheable()) { 441 // This transaction will get a read-shared copy, downgrading 442 // our copy if we had a writable one 443 postDowngrade = true; 444 // make sure that any downstream cache does not respond with a 445 // writable (and dirty) copy even if it has one, unless it was 446 // explicitly asked for one 447 pkt->setHasSharers(); 448 } 449 450 return true; 451} 452 453 454bool 455MSHR::promoteDeferredTargets() 456{ 457 assert(targets.empty()); 458 if (deferredTargets.empty()) { 459 return false; 460 } 461 462 // swap targets & deferredTargets lists 463 std::swap(targets, deferredTargets); 464 465 // clear deferredTargets flags 466 deferredTargets.resetFlags(); 467 468 order = targets.front().order; 469 readyTime = std::max(curTick(), targets.front().readyTime); 470 471 return true; 472} 473 474 475void 476MSHR::promoteWritable() 477{ 478 if (deferredTargets.needsWritable && 479 !(hasPostInvalidate() || hasPostDowngrade())) { 480 // We got a writable response, but we have deferred targets 481 // which are waiting to request a writable copy (not because 482 // of a pending invalidate). This can happen if the original 483 // request was for a read-only block, but we got a writable 484 // response anyway. Since we got the writable copy there's no 485 // need to defer the targets, so move them up to the regular 486 // target list. 487 assert(!targets.needsWritable); 488 targets.needsWritable = true; 489 // if any of the deferred targets were upper-level cache 490 // requests marked downstreamPending, need to clear that 491 assert(!downstreamPending); // not pending here anymore 492 deferredTargets.clearDownstreamPending(); 493 // this clears out deferredTargets too 494 targets.splice(targets.end(), deferredTargets); 495 deferredTargets.resetFlags(); 496 } 497} 498 499 500bool 501MSHR::checkFunctional(PacketPtr pkt) 502{ 503 // For printing, we treat the MSHR as a whole as single entity. 504 // For other requests, we iterate over the individual targets 505 // since that's where the actual data lies. 506 if (pkt->isPrint()) { 507 pkt->checkFunctional(this, blkAddr, isSecure, blkSize, NULL); 508 return false; 509 } else { 510 return (targets.checkFunctional(pkt) || 511 deferredTargets.checkFunctional(pkt)); 512 } 513} 514 515 516void 517MSHR::print(std::ostream &os, int verbosity, const std::string &prefix) const 518{ 519 ccprintf(os, "%s[%#llx:%#llx](%s) %s %s %s state: %s %s %s %s %s\n", 520 prefix, blkAddr, blkAddr + blkSize - 1, 521 isSecure ? "s" : "ns", 522 isForward ? "Forward" : "", 523 allocOnFill ? "AllocOnFill" : "", 524 isForwardNoResponse() ? "ForwNoResp" : "", 525 needsWritable() ? "Wrtbl" : "", 526 _isUncacheable ? "Unc" : "", 527 inService ? "InSvc" : "", 528 downstreamPending ? "DwnPend" : "", 529 hasPostInvalidate() ? "PostInv" : "", 530 hasPostDowngrade() ? "PostDowngr" : ""); 531 532 ccprintf(os, "%s Targets:\n", prefix); 533 targets.print(os, verbosity, prefix + " "); 534 if (!deferredTargets.empty()) { 535 ccprintf(os, "%s Deferred Targets:\n", prefix); 536 deferredTargets.print(os, verbosity, prefix + " "); 537 } 538} 539 540std::string 541MSHR::print() const 542{ 543 ostringstream str; 544 print(str); 545 return str.str(); 546} 547