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authorAndreas Hansson <andreas.hansson@arm.com>2015-12-31 09:33:39 -0500
committerAndreas Hansson <andreas.hansson@arm.com>2015-12-31 09:33:39 -0500
commit7fca994d04230f1e41b9443b33f891460fc5368d (patch)
tree3bd62bc958f5c81b68c3517d3ed3251203790036
parentf1ec326be59b137ff0955b4d80e6516754016fd5 (diff)
downloadgem5-7fca994d04230f1e41b9443b33f891460fc5368d.tar.xz
mem: Do not allocate space for packet data if not needed
This patch looks at the request and response command to determine if either actually has any data payload, and if not, we do not allocate any space for packet data. The only tricky case is where the command type is changed as part of the MSHR functionality. In these cases where the original packet had no data, but the new packet does, we need to explicitly call allocate().
-rw-r--r--src/mem/cache/cache.cc14
-rw-r--r--src/mem/cache/mshr.cc16
-rw-r--r--src/mem/packet.hh15
3 files changed, 37 insertions, 8 deletions
diff --git a/src/mem/cache/cache.cc b/src/mem/cache/cache.cc
index 991463d76..9050a1c30 100644
--- a/src/mem/cache/cache.cc
+++ b/src/mem/cache/cache.cc
@@ -185,7 +185,11 @@ Cache::satisfyCpuSideRequest(PacketPtr pkt, CacheBlk *blk,
if (pkt->isLLSC()) {
blk->trackLoadLocked(pkt);
}
+
+ // all read responses have a data payload
+ assert(pkt->hasRespData());
pkt->setDataFromBlock(blk->data, blkSize);
+
// determine if this read is from a (coherent) cache, or not
// by looking at the command type; we could potentially add a
// packet attribute such as 'FromCache' to make this check a
@@ -796,10 +800,7 @@ Cache::recvTimingReq(PacketPtr pkt)
}
pkt->makeTimingResponse();
- // for debugging, set all the bits in the response data
- // (also keeps valgrind from complaining when debugging settings
- // print out instruction results)
- std::memset(pkt->getPtr<uint8_t>(), 0xFF, pkt->getSize());
+
// request_time is used here, taking into account lat and the delay
// charged if the packet comes from the xbar.
cpuSidePort->schedTimingResp(pkt, request_time, true);
@@ -2041,7 +2042,10 @@ Cache::handleSnoop(PacketPtr pkt, CacheBlk *blk, bool is_timing,
doTimingSupplyResponse(pkt, blk->data, is_deferred, pending_inval);
} else {
pkt->makeAtomicResponse();
- pkt->setDataFromBlock(blk->data, blkSize);
+ // packets such as upgrades do not actually have any data
+ // payload
+ if (pkt->hasData())
+ pkt->setDataFromBlock(blk->data, blkSize);
}
}
diff --git a/src/mem/cache/mshr.cc b/src/mem/cache/mshr.cc
index e2141a429..1d18a2861 100644
--- a/src/mem/cache/mshr.cc
+++ b/src/mem/cache/mshr.cc
@@ -115,6 +115,9 @@ MSHR::TargetList::add(PacketPtr pkt, Tick readyTime,
static void
replaceUpgrade(PacketPtr pkt)
{
+ // remember if the current packet has data allocated
+ bool has_data = pkt->hasData() || pkt->hasRespData();
+
if (pkt->cmd == MemCmd::UpgradeReq) {
pkt->cmd = MemCmd::ReadExReq;
DPRINTF(Cache, "Replacing UpgradeReq with ReadExReq\n");
@@ -125,6 +128,19 @@ replaceUpgrade(PacketPtr pkt)
pkt->cmd = MemCmd::StoreCondFailReq;
DPRINTF(Cache, "Replacing StoreCondReq with StoreCondFailReq\n");
}
+
+ if (!has_data) {
+ // there is no sensible way of setting the data field if the
+ // new command actually would carry data
+ assert(!pkt->hasData());
+
+ if (pkt->hasRespData()) {
+ // we went from a packet that had no data (neither request,
+ // nor response), to one that does, and therefore we need to
+ // actually allocate space for the data payload
+ pkt->allocate();
+ }
+ }
}
diff --git a/src/mem/packet.hh b/src/mem/packet.hh
index 4614799bf..94508f697 100644
--- a/src/mem/packet.hh
+++ b/src/mem/packet.hh
@@ -508,6 +508,11 @@ class Packet : public Printable
bool isEviction() const { return cmd.isEviction(); }
bool isWriteback() const { return cmd.isWriteback(); }
bool hasData() const { return cmd.hasData(); }
+ bool hasRespData() const
+ {
+ MemCmd resp_cmd = cmd.responseCommand();
+ return resp_cmd.hasData();
+ }
bool isLLSC() const { return cmd.isLLSC(); }
bool isError() const { return cmd.isError(); }
bool isPrint() const { return cmd.isPrint(); }
@@ -1058,9 +1063,13 @@ class Packet : public Printable
void
allocate()
{
- assert(flags.noneSet(STATIC_DATA|DYNAMIC_DATA));
- flags.set(DYNAMIC_DATA);
- data = new uint8_t[getSize()];
+ // if either this command or the response command has a data
+ // payload, actually allocate space
+ if (hasData() || hasRespData()) {
+ assert(flags.noneSet(STATIC_DATA|DYNAMIC_DATA));
+ flags.set(DYNAMIC_DATA);
+ data = new uint8_t[getSize()];
+ }
}
/** @} */