mem: Clarification of packet crossbar timings

This patch clarifies the packet timings annotated
when going through a crossbar.

The old 'firstWordDelay' is replaced by 'headerDelay' that represents
the delay associated to the delivery of the header of the packet.

The old 'lastWordDelay' is replaced by 'payloadDelay' that represents
the delay needed to processing the payload of the packet.

For now the uses and values remain identical. However, going forward
the payloadDelay will be additive, and not include the
headerDelay. Follow-on patches will make the headerDelay capture the
pipeline latency incurred in the crossbar, whereas the payloadDelay
will capture the additional serialisation delay.

1 files changed, 8 insertions, 8 deletions

diff --git a/src/mem/coherent_xbar.cc b/src/mem/coherent_xbar.cc
index 02580702b..454de69ce 100644
--- a/src/mem/coherent_xbar.cc
+++ b/src/mem/coherent_xbar.cc
@@ -168,7 +168,7 @@ CoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
     unsigned int pkt_cmd = pkt->cmdToIndex();
 
     calcPacketTiming(pkt);
-    Tick packetFinishTime = pkt->lastWordDelay + curTick();
+    Tick packetFinishTime = curTick() + pkt->payloadDelay;
 
     // uncacheable requests need never be snooped
     if (!pkt->req->isUncacheable() && !system->bypassCaches()) {
@@ -222,7 +222,7 @@ CoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
         assert(!pkt->memInhibitAsserted());
 
         // undo the calculation so we can check for 0 again
-        pkt->firstWordDelay = pkt->lastWordDelay = 0;
+        pkt->headerDelay = pkt->payloadDelay = 0;
 
         DPRINTF(CoherentXBar, "recvTimingReq: src %s %s 0x%x RETRY\n",
                 src_port->name(), pkt->cmdString(), pkt->getAddr());
@@ -301,7 +301,7 @@ CoherentXBar::recvTimingResp(PacketPtr pkt, PortID master_port_id)
     unsigned int pkt_cmd = pkt->cmdToIndex();
 
     calcPacketTiming(pkt);
-    Tick packetFinishTime = pkt->lastWordDelay + curTick();
+    Tick packetFinishTime = curTick() + pkt->payloadDelay;
 
     if (snoopFilter && !pkt->req->isUncacheable() && !system->bypassCaches()) {
         // let the snoop filter inspect the response and update its state
@@ -427,7 +427,7 @@ CoherentXBar::recvTimingSnoopResp(PacketPtr pkt, PortID slave_port_id)
     assert(!pkt->isExpressSnoop());
 
     calcPacketTiming(pkt);
-    Tick packetFinishTime = pkt->lastWordDelay + curTick();
+    Tick packetFinishTime = curTick() + pkt->payloadDelay;
 
     // forward it either as a snoop response or a normal response
     if (forwardAsSnoop) {
@@ -608,8 +608,8 @@ CoherentXBar::recvAtomic(PacketPtr pkt, PortID slave_port_id)
         transDist[pkt_cmd]++;
     }
 
-    // @todo: Not setting first-word time
-    pkt->lastWordDelay = response_latency;
+    // @todo: Not setting header time
+    pkt->payloadDelay = response_latency;
     return response_latency;
 }
 
@@ -648,8 +648,8 @@ CoherentXBar::recvAtomicSnoop(PacketPtr pkt, PortID master_port_id)
         snoops++;
     }
 
-    // @todo: Not setting first-word time
-    pkt->lastWordDelay = snoop_response_latency;
+    // @todo: Not setting header time
+    pkt->payloadDelay = snoop_response_latency;
     return snoop_response_latency;
 }