changeset c04dc66e4316 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=c04dc66e4316
description:
mem: Remove WriteInvalidate support
Prepare for a different implementation following in the next patch
diffstat:
src/mem/cache/base.hh | 1 -
src/mem/cache/blk.hh | 3 -
src/mem/cache/cache_impl.hh | 189 ++++---------------------------------------
src/mem/cache/mshr.cc | 25 +----
src/mem/cache/mshr.hh | 18 ----
5 files changed, 25 insertions(+), 211 deletions(-)
diffs (truncated from 469 to 300 lines):
diff -r 7c4f1d0a8cff -r c04dc66e4316 src/mem/cache/base.hh
--- a/src/mem/cache/base.hh Tue Dec 02 06:08:15 2014 -0500
+++ b/src/mem/cache/base.hh Tue Dec 02 06:08:17 2014 -0500
@@ -94,7 +94,6 @@
Blocked_NoMSHRs = MSHRQueue_MSHRs,
Blocked_NoWBBuffers = MSHRQueue_WriteBuffer,
Blocked_NoTargets,
- Blocked_PendingWriteInvalidate,
NUM_BLOCKED_CAUSES
};
diff -r 7c4f1d0a8cff -r c04dc66e4316 src/mem/cache/blk.hh
--- a/src/mem/cache/blk.hh Tue Dec 02 06:08:15 2014 -0500
+++ b/src/mem/cache/blk.hh Tue Dec 02 06:08:17 2014 -0500
@@ -73,9 +73,6 @@
BlkHWPrefetched = 0x20,
/** block holds data from the secure memory space */
BlkSecure = 0x40,
- /** can the block transition to E? (hasn't been shared with another cache)
- * used to close a timing gap when handling WriteInvalidate packets */
- BlkCanGoExclusive = 0x80
};
/**
diff -r 7c4f1d0a8cff -r c04dc66e4316 src/mem/cache/cache_impl.hh
--- a/src/mem/cache/cache_impl.hh Tue Dec 02 06:08:15 2014 -0500
+++ b/src/mem/cache/cache_impl.hh Tue Dec 02 06:08:17 2014 -0500
@@ -70,7 +70,7 @@
: BaseCache(p),
tags(dynamic_cast<TagStore*>(p->tags)),
prefetcher(p->prefetcher),
- doFastWrites(true),
+ doFastWrites(false),
prefetchOnAccess(p->prefetch_on_access)
{
tempBlock = new BlkType();
@@ -321,20 +321,15 @@
pkt->getAddr(), pkt->isSecure() ? "s" : "ns",
blk ? "hit" : "miss", blk ? blk->print() : "");
- // Writeback handling is special case. We can write the block
- // into the cache without having a writeable copy (or any copy at
- // all). Like writebacks, we write into the cache upon initial
- // receipt of a write-invalidate packets as well.
- if ((pkt->cmd == MemCmd::Writeback) ||
- ((pkt->cmd == MemCmd::WriteInvalidateReq) && isTopLevel)) {
+ // Writeback handling is special case. We can write the block into
+ // the cache without having a writeable copy (or any copy at all).
+ if (pkt->cmd == MemCmd::Writeback) {
assert(blkSize == pkt->getSize());
if (blk == NULL) {
// need to do a replacement
blk = allocateBlock(pkt->getAddr(), pkt->isSecure(), writebacks);
if (blk == NULL) {
- // no replaceable block available, give up.
- // Writeback will be forwarded to next level,
- // WriteInvalidate will be retried.
+ // no replaceable block available: give up, fwd to next level.
incMissCount(pkt);
return false;
}
@@ -345,29 +340,16 @@
blk->status |= BlkSecure;
}
}
- if (pkt->cmd == MemCmd::Writeback) {
- blk->status |= BlkDirty;
- if (pkt->isSupplyExclusive()) {
- blk->status |= BlkWritable;
- }
- // nothing else to do; writeback doesn't expect response
- assert(!pkt->needsResponse());
- } else if (pkt->cmd == MemCmd::WriteInvalidateReq) {
- blk->status |= (BlkReadable | BlkDirty | BlkCanGoExclusive);
- blk->status &= ~BlkWritable;
- ++fastWrites;
+ blk->status |= BlkDirty;
+ if (pkt->isSupplyExclusive()) {
+ blk->status |= BlkWritable;
}
+ // nothing else to do; writeback doesn't expect response
+ assert(!pkt->needsResponse());
std::memcpy(blk->data, pkt->getConstPtr<uint8_t>(), blkSize);
DPRINTF(Cache, "%s new state is %s\n", __func__, blk->print());
incHitCount(pkt);
return true;
- } else if ((pkt->cmd == MemCmd::WriteInvalidateReq) && !isTopLevel) {
- if (blk != NULL) {
- assert(blk != tempBlock);
- tags->invalidate(blk);
- blk->invalidate();
- }
- return true;
} else if ((blk != NULL) &&
(pkt->needsExclusive() ? blk->isWritable()
: blk->isReadable())) {
@@ -550,18 +532,6 @@
bool needsResponse = pkt->needsResponse();
- if (pkt->cmd == MemCmd::WriteInvalidateReq) {
- if (!satisfied && isTopLevel) {
- // access() tried to allocate a block but it could not; abort.
- setBlocked(Blocked_PendingWriteInvalidate);
- return false;
- }
- satisfied = false;
- // we need to take the miss path (allocate MSHR, etc.) for
- // WriteInvalidates because they always need to propagate
- // throughout the memory system
- }
-
if (satisfied) {
// hit (for all other request types)
@@ -591,16 +561,6 @@
// @todo: Make someone pay for this
pkt->firstWordDelay = pkt->lastWordDelay = 0;
- if (blk && blk->isValid() && (blk->status & BlkCanGoExclusive) &&
- pkt->isWrite() && (pkt->cmd != MemCmd::WriteInvalidateReq)) {
- // Packet is a Write (needs exclusive) should be delayed because
- // a WriteInvalidate is pending. Instead of going the MSHR route,
- // the Packet should be replayed, since if the block transitions
- // to Exclusive the write can complete immediately.
- setBlocked(Blocked_PendingWriteInvalidate);
- return false;
- }
-
Addr blk_addr = blockAlign(pkt->getAddr());
MSHR *mshr = mshrQueue.findMatch(blk_addr, pkt->isSecure());
@@ -647,20 +607,7 @@
pkt = pf;
}
- if (pkt && (pkt->cmd == MemCmd::WriteInvalidateReq)) {
- // WriteInvalidates cannot coalesce with other requests, so
- // we cannot use an existing MSHR. If one exists, we mark it
- // as 'obsolete' so they don't modify the cache.
- if (mshr) {
- // Everything up to this point is obsolete, meaning
- // they should not modify the cache.
- DPRINTF(Cache, "%s: marking MSHR obsolete in %s of %x\n",
- __func__, pkt->cmdString(), pkt->getAddr());
-
- mshr->markObsolete();
- }
- allocateMissBuffer(pkt, time, true);
- } else if (mshr) {
+ if (mshr) {
/// MSHR hit
/// @note writebacks will be checked in getNextMSHR()
/// for any conflicting requests to the same block
@@ -707,10 +654,7 @@
if (pkt->cmd == MemCmd::Writeback) {
allocateWriteBuffer(pkt, time, true);
} else {
- if (pkt->cmd == MemCmd::WriteInvalidateReq) {
- // a WriteInvalidate is not a normal write miss;
- // the assertions below are not applicable.
- } else if (blk && blk->isValid()) {
+ if (blk && blk->isValid()) {
// If we have a write miss to a valid block, we
// need to mark the block non-readable. Otherwise
// if we allow reads while there's an outstanding
@@ -769,12 +713,6 @@
return NULL;
}
- // WriteInvalidates for cache line clearing instructions don't
- // require a read; just send directly to the bus.
- if (cpu_pkt->cmd == MemCmd::WriteInvalidateReq) {
- return NULL;
- }
-
if (!blkValid &&
(cpu_pkt->cmd == MemCmd::Writeback || cpu_pkt->isUpgrade())) {
// Writebacks that weren't allocated in access() and upgrades
@@ -870,9 +808,6 @@
if (!access(pkt, blk, lat, writebacks)) {
// MISS
- // WriteInvalidates should never fail an access() in Atomic mode
- assert(pkt->cmd != MemCmd::WriteInvalidateReq);
-
PacketPtr bus_pkt = getBusPacket(pkt, blk, pkt->needsExclusive());
bool is_forward = (bus_pkt == NULL);
@@ -943,29 +878,6 @@
delete wbPkt;
}
- // We now have the block one way or another (hit or completed miss),
- // except for Request types that perform an invalidate, where the point
- // is to make sure there is no block.
-
- if (pkt->cmd == MemCmd::WriteInvalidateReq) {
- memSidePort->sendAtomic(pkt); // complete writeback
- if (isTopLevel) {
- // @todo Static analysis suggests this can actually happen
- assert(blk);
-
- // top level caches allocate and write the data
- assert(blk->isDirty());
- assert(!blk->isWritable());
- assert(blk->status & BlkCanGoExclusive);
- blk->status &= ~(BlkDirty | BlkCanGoExclusive); // and mark clean
- blk->status |= BlkWritable; // i.e. O(+cgE) ->
E
- } else {
- // other caches invalidate.
- // if the block was found, it was invalidated.
- assert(!blk || !blk->isValid());
- }
- }
-
if (pkt->needsResponse()) {
pkt->makeAtomicResponse();
}
@@ -1101,10 +1013,7 @@
bool is_fill = !mshr->isForward &&
(pkt->isRead() || pkt->cmd == MemCmd::UpgradeResp);
- if (mshr->isObsolete()) {
- DPRINTF(Cache, "%s: skipping cache fills; data for %s of %x "
- "is obsolete\n", __func__, pkt->cmdString(), pkt->getAddr());
- } else if (is_fill && !is_error) {
+ if (is_fill && !is_error) {
DPRINTF(Cache, "Block for addr %x being updated in Cache\n",
pkt->getAddr());
@@ -1140,19 +1049,9 @@
}
if (is_fill) {
- // Presently the only situation leading to 'obsolete'
- // data is when a WriteInvalidate blows away an already
- // pending/in-progress read. We don't want to overwrite
- // cache data in that case.
- if (mshr->isObsolete()) {
- DPRINTF(Cache, "%s: skipping satisfyCpuSideRequest; "
- "data for %s of %x is obsolete\n",
- __func__, target->pkt->cmdString(),
- target->pkt->getAddr());
- } else {
- satisfyCpuSideRequest(target->pkt, blk,
- true, mshr->hasPostDowngrade());
- }
+ 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;
@@ -1184,38 +1083,6 @@
completion_time = clockEdge(responseLatency) +
pkt->lastWordDelay;
target->pkt->req->setExtraData(0);
- } else if (pkt->cmd == MemCmd::WriteInvalidateResp) {
- if (blk) {
- assert(blk->isDirty() && !blk->isWritable());
- // The block, having been written back, is no longer dirty,
- // nor do we have any reason to see if it was snooped in
the
- // meantime (which CanGoExclusive tracks). If it can go
- // exclusive, we put it in that state, and otherwise S.
- // In short: O(+cgE) -> E, O(-cgE) -> S
- if (blk->status & BlkCanGoExclusive) {
- blk->status |= BlkWritable;
- }
- blk->status &= ~(BlkDirty | BlkCanGoExclusive);
- }
- if (isTopLevel) {
- // makeTimingResponse() will turn it into a WriteResp
- target->pkt->cmd = MemCmd::WriteReq;
- // Writes may have been blocked - quite rare case, but
- // it does happen. Prevent deadlock by telling the core
- if (isBlocked()) { // to retry.
- clearBlocked(Blocked_PendingWriteInvalidate);
- }
- }
- // If the block managed to get evicted before its own
- // writeback (e.g. by a Read/Upgrade (from O(-cgE)/S to
- // I/E) or ReadExclusive (direct to I/E); either way a
- // cache-to-cache ownership transfer) completed, that's
- // OK, we just ignore this response. If the new owner
- // doesn't actually modify it, a superfluous writeback
- // will occur for its impatience (since it will think it
- // has dirty data), but it really can't be helped.
- completion_time = clockEdge(responseLatency) +
- pkt->lastWordDelay;
} else {
// not a cache fill, just forwarding response
// responseLatency is the latency of the return path
@@ -1443,8 +1310,7 @@
Addr repl_addr = tags->regenerateBlkAddr(blk->tag, blk->set);
MSHR *repl_mshr = mshrQueue.findMatch(repl_addr, blk->isSecure());
if (repl_mshr) {
- // must be an outstanding upgrade request (common case)
- // or WriteInvalidate pending writeback (very uncommon case)
+ // must be an outstanding upgrade request
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