src/mem/cache/mshr.cc

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