return mshr;
}
- void markInServiceInternal(MSHR *mshr)
+ void markInServiceInternal(MSHR *mshr, PacketPtr pkt)
{
MSHRQueue *mq = mshr->queue;
bool wasFull = mq->isFull();
- mq->markInService(mshr);
+ mq->markInService(mshr, pkt);
if (wasFull && !mq->isFull()) {
clearBlocked((BlockedCause)mq->index);
}
BlkType *handleFill(PacketPtr pkt, BlkType *blk,
PacketList &writebacks);
- void satisfyCpuSideRequest(PacketPtr pkt, BlkType *blk);
+ void satisfyCpuSideRequest(PacketPtr pkt, BlkType *blk,
+ bool deferred_response = false,
+ bool pending_downgrade = false);
bool satisfyMSHR(MSHR *mshr, PacketPtr pkt, BlkType *blk);
void doTimingSupplyResponse(PacketPtr req_pkt, uint8_t *blk_data,
* are successfully sent.
* @param pkt The request that was sent on the bus.
*/
- void markInService(MSHR *mshr);
+ void markInService(MSHR *mshr, PacketPtr pkt = 0);
/**
* Perform the given writeback request.
template<class TagStore>
void
-Cache<TagStore>::satisfyCpuSideRequest(PacketPtr pkt, BlkType *blk)
+Cache<TagStore>::satisfyCpuSideRequest(PacketPtr pkt, BlkType *blk,
+ bool deferred_response,
+ bool pending_downgrade)
{
- assert(blk);
+ assert(blk && blk->isValid());
// Occasionally this is not true... if we are a lower-level cache
// satisfying a string of Read and ReadEx requests from
// upper-level caches, a Read will mark the block as shared but we
// can satisfy a following ReadEx anyway since we can rely on the
// Read requester(s) to have buffered the ReadEx snoop and to
// invalidate their blocks after receiving them.
- // assert(pkt->needsExclusive() ? blk->isWritable() : blk->isValid());
+ // assert(!pkt->needsExclusive() || blk->isWritable());
assert(pkt->getOffset(blkSize) + pkt->getSize() <= blkSize);
// Check RMW operations first since both isRead() and
// special handling for coherent block requests from
// upper-level caches
if (pkt->needsExclusive()) {
- // on ReadExReq we give up our copy
+ // if we have a dirty copy, make sure the recipient
+ // keeps it marked dirty
+ if (blk->isDirty()) {
+ pkt->assertMemInhibit();
+ }
+ // on ReadExReq we give up our copy unconditionally
tags->invalidateBlk(blk);
+ } else if (blk->isWritable() && !pending_downgrade
+ && !pkt->sharedAsserted()) {
+ // we can give the requester an exclusive copy (by not
+ // asserting shared line) on a read request if:
+ // - we have an exclusive copy at this level (& below)
+ // - we don't have a pending snoop from below
+ // signaling another read request
+ // - no other cache above has a copy (otherwise it
+ // would have asseretd shared line on request)
+
+ if (blk->isDirty()) {
+ // special considerations if we're owner:
+ if (!deferred_response) {
+ // if we are responding immediately and can
+ // signal that we're transferring ownership
+ // along with exclusivity, do so
+ pkt->assertMemInhibit();
+ blk->status &= ~BlkDirty;
+ } else {
+ // if we're responding after our own miss,
+ // there's a window where the recipient didn't
+ // know it was getting ownership and may not
+ // have responded to snoops correctly, so we
+ // can't pass off ownership *or* exclusivity
+ pkt->assertShared();
+ }
+ }
} else {
- // on ReadReq we create shareable copies here and in
- // the requester
+ // otherwise only respond with a shared copy
pkt->assertShared();
- blk->status &= ~BlkWritable;
}
}
} else {
template<class TagStore>
void
-Cache<TagStore>::markInService(MSHR *mshr)
+Cache<TagStore>::markInService(MSHR *mshr, PacketPtr pkt)
{
- markInServiceInternal(mshr);
+ markInServiceInternal(mshr, pkt);
#if 0
if (mshr->originalCmd == MemCmd::HardPFReq) {
DPRINTF(HWPrefetch, "%s:Marking a HW_PF in service\n",
case MSHR::Target::FromCPU:
Tick completion_time;
if (is_fill) {
- satisfyCpuSideRequest(target->pkt, blk);
+ satisfyCpuSideRequest(target->pkt, blk,
+ true, mshr->hasPostDowngrade());
// How many bytes past the first request is this one
int transfer_offset =
target->pkt->getOffset(blkSize) - initial_offset;
// if this packet is an error copy that to the new packet
if (is_error)
target->pkt->copyError(pkt);
- if (pkt->isInvalidate()) {
+ if (target->pkt->cmd == MemCmd::ReadResp &&
+ (pkt->isInvalidate() || mshr->hasPostInvalidate())) {
// If intermediate cache got ReadRespWithInvalidate,
// propagate that. Response should not have
// isInvalidate() set otherwise.
- assert(target->pkt->cmd == MemCmd::ReadResp);
- assert(pkt->cmd == MemCmd::ReadRespWithInvalidate);
target->pkt->cmd = MemCmd::ReadRespWithInvalidate;
}
cpuSidePort->respond(target->pkt, completion_time);
assert(!is_error);
// response to snoop request
DPRINTF(Cache, "processing deferred snoop...\n");
+ assert(!(pkt->isInvalidate() && !mshr->hasPostInvalidate()));
handleSnoop(target->pkt, blk, true, true,
- mshr->pendingInvalidate || pkt->isInvalidate());
+ mshr->hasPostInvalidate());
break;
default:
mshr->popTarget();
}
- if (pkt->isInvalidate()) {
- tags->invalidateBlk(blk);
+ if (blk) {
+ if (pkt->isInvalidate() || mshr->hasPostInvalidate()) {
+ tags->invalidateBlk(blk);
+ } else if (mshr->hasPostDowngrade()) {
+ blk->status &= ~BlkWritable;
+ }
}
if (mshr->promoteDeferredTargets()) {
// avoid later read getting stale data while write miss is
// outstanding.. see comment in timingAccess()
- blk->status &= ~BlkReadable;
+ if (blk) {
+ blk->status &= ~BlkReadable;
+ }
MSHRQueue *mq = mshr->queue;
mq->markPending(mshr);
requestMemSideBus((RequestCause)mq->index, pkt->finishTime);
int id = pkt->req->hasContextId() ? pkt->req->contextId() : -1;
tags->insertBlock(pkt->getAddr(), blk, id);
}
+
+ // starting from scratch with a new block
+ blk->status = 0;
} else {
// existing block... probably an upgrade
assert(blk->tag == tags->extractTag(addr));
// either we're getting new data or the block should already be valid
assert(pkt->hasData() || blk->isValid());
+ // don't clear block status... if block is already dirty we
+ // don't want to lose that
}
- blk->status = BlkValid | BlkReadable;
+ blk->status |= BlkValid | BlkReadable;
if (!pkt->sharedAsserted()) {
blk->status |= BlkWritable;
delete pkt;
}
} else {
- myCache()->markInService(mshr);
+ myCache()->markInService(mshr, pkt);
}
}
}
}
+static void
+replaceUpgrade(PacketPtr pkt)
+{
+ if (pkt->cmd == MemCmd::UpgradeReq) {
+ pkt->cmd = MemCmd::ReadExReq;
+ DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n");
+ } else if (pkt->cmd == MemCmd::SCUpgradeReq) {
+ pkt->cmd = MemCmd::SCUpgradeFailReq;
+ DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
+ }
+}
+
+
void
MSHR::TargetList::replaceUpgrades()
{
Iterator end_i = end();
for (Iterator i = begin(); i != end_i; ++i) {
- if (i->pkt->cmd == MemCmd::UpgradeReq) {
- i->pkt->cmd = MemCmd::ReadExReq;
- DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n");
- } else if (i->pkt->cmd == MemCmd::SCUpgradeReq) {
- i->pkt->cmd = MemCmd::SCUpgradeFailReq;
- DPRINTF(Cache, "Replacing SCUpgradeReq with SCUpgradeFailReq\n");
- }
+ replaceUpgrade(i->pkt);
}
hasUpgrade = false;
Target::FromPrefetcher : Target::FromCPU;
targets->add(target, whenReady, _order, source, true);
assert(deferredTargets->isReset());
- pendingInvalidate = false;
- pendingShared = false;
data = NULL;
}
}
bool
-MSHR::markInService()
+MSHR::markInService(PacketPtr pkt)
{
assert(!inService);
if (isForwardNoResponse()) {
return true;
}
inService = true;
+ pendingDirty = (targets->needsExclusive ||
+ (!pkt->sharedAsserted() && pkt->memInhibitAsserted()));
+ postInvalidate = postDowngrade = false;
+
if (!downstreamPending) {
// let upstream caches know that the request has made it to a
// level where it's going to get a response
assert(deferredTargets->isReset());
assert(ntargets == 0);
inService = false;
- //allocIter = NULL;
- //readyIter = NULL;
}
/*
// - there are other targets already deferred
// - there's a pending invalidate to be applied after the response
// comes back (but before this target is processed)
- // - the outstanding request is for a non-exclusive block and this
- // target requires an exclusive block
+ // - this target requires an exclusive block and either we're not
+ // getting an exclusive block back or we have already snooped
+ // another read request that will downgrade our exclusive block
+ // to shared
// assume we'd never issue a prefetch when we've got an
// outstanding miss
assert(pkt->cmd != MemCmd::HardPFReq);
if (inService &&
- (!deferredTargets->empty() || pendingInvalidate ||
- (!targets->needsExclusive && pkt->needsExclusive()))) {
+ (!deferredTargets->empty() || hasPostInvalidate() ||
+ (pkt->needsExclusive() &&
+ (!isPendingDirty() || hasPostDowngrade() || isForward)))) {
// need to put on deferred list
+ if (hasPostInvalidate())
+ replaceUpgrade(pkt);
deferredTargets->add(pkt, whenReady, _order, Target::FromCPU, true);
} else {
// No request outstanding, or still OK to append to
// From here on down, the request issued by this MSHR logically
// precedes the request we're snooping.
-
if (pkt->needsExclusive()) {
// snooped request still precedes the re-request we'll have to
// issue for deferred targets, if any...
deferredTargets->replaceUpgrades();
}
- if (pendingInvalidate) {
+ if (hasPostInvalidate()) {
// a prior snoop has already appended an invalidation, so
// logically we don't have the block anymore; no need for
// further snooping.
return true;
}
- if (targets->needsExclusive || pkt->needsExclusive()) {
- // actual target device (typ. PhysicalMemory) will delete the
- // packet on reception, so we need to save a copy here
+ if (isPendingDirty() || pkt->isInvalidate()) {
+ // We need to save and replay the packet in two cases:
+ // 1. We're awaiting an exclusive copy, so ownership is pending,
+ // and we need to respond after we receive data.
+ // 2. It's an invalidation (e.g., UpgradeReq), and we need
+ // to forward the snoop up the hierarchy after the current
+ // transaction completes.
+
+ // Actual target device (typ. PhysicalMemory) will delete the
+ // packet on reception, so we need to save a copy here.
PacketPtr cp_pkt = new Packet(pkt, true);
targets->add(cp_pkt, curTick, _order, Target::FromSnoop,
downstreamPending && targets->needsExclusive);
++ntargets;
- if (targets->needsExclusive) {
- // We're awaiting an exclusive copy, so ownership is pending.
- // It's up to us to respond once the data arrives.
+ if (isPendingDirty()) {
pkt->assertMemInhibit();
pkt->setSupplyExclusive();
- } else {
- // Someone else may respond before we get around to
- // processing this snoop, which means the copied request
- // pointer will no longer be valid
- cp_pkt->req = NULL;
}
if (pkt->needsExclusive()) {
// This transaction will take away our pending copy
- pendingInvalidate = true;
+ postInvalidate = true;
}
- } else {
- // Read to a read: no conflict, so no need to record as
- // target, but make sure neither reader thinks he's getting an
- // exclusive copy
- pendingShared = true;
+ }
+
+ if (!pkt->needsExclusive()) {
+ // This transaction will get a read-shared copy, downgrading
+ // our copy if we had an exclusive one
+ postDowngrade = true;
pkt->assertShared();
}
// clear deferredTargets flags
deferredTargets->resetFlags();
- pendingInvalidate = false;
- pendingShared = false;
order = targets->front().order;
readyTime = std::max(curTick, targets->front().readyTime);
void
MSHR::handleFill(Packet *pkt, CacheBlk *blk)
{
- if (pendingShared) {
- // we snooped another read while this read was in
- // service... assert shared line on its behalf
- pkt->assertShared();
- }
-
- if (!pkt->sharedAsserted() && !pendingInvalidate
+ if (!pkt->sharedAsserted()
+ && !(hasPostInvalidate() || hasPostDowngrade())
&& deferredTargets->needsExclusive) {
// We got an exclusive response, but we have deferred targets
// which are waiting to request an exclusive copy (not because
_isUncacheable ? "Unc" : "",
inService ? "InSvc" : "",
downstreamPending ? "DwnPend" : "",
- pendingInvalidate ? "PendInv" : "",
- pendingShared ? "PendShared" : "");
+ hasPostInvalidate() ? "PostInv" : "",
+ hasPostDowngrade() ? "PostDowngr" : "");
ccprintf(os, "%s Targets:\n", prefix);
targets->print(os, verbosity, prefix + " ");
bool downstreamPending;
- bool pendingInvalidate;
- bool pendingShared;
+ /** The pending* and post* flags are only valid if inService is
+ * true. Using the accessor functions lets us detect if these
+ * flags are accessed improperly.
+ */
+
+ /** Will we have a dirty copy after this request? */
+ bool pendingDirty;
+ bool isPendingDirty() const {
+ assert(inService); return pendingDirty;
+ }
+
+ /** Did we snoop an invalidate while waiting for data? */
+ bool postInvalidate;
+ bool hasPostInvalidate() const {
+ assert(inService); return postInvalidate;
+ }
+
+ /** Did we snoop a read while waiting for data? */
+ bool postDowngrade;
+ bool hasPostDowngrade() const {
+ assert(inService); return postDowngrade;
+ }
/** Thread number of the miss. */
ThreadID threadNum;
void allocate(Addr addr, int size, PacketPtr pkt,
Tick when, Counter _order);
- bool markInService();
+ bool markInService(PacketPtr pkt);
void clearDownstreamPending();
}
void
-MSHRQueue::markInService(MSHR *mshr)
+MSHRQueue::markInService(MSHR *mshr, PacketPtr pkt)
{
- if (mshr->markInService()) {
+ if (mshr->markInService(pkt)) {
deallocate(mshr);
} else {
readyList.erase(mshr->readyIter);
* readyList. Deallocates the MSHR if it does not expect a response.
* @param mshr The MSHR to mark in service.
*/
- void markInService(MSHR *mshr);
+ void markInService(MSHR *mshr, PacketPtr pkt);
/**
* Mark an in service entry as pending, used to resend a request.
projects / gem5.git / commitdiff