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mem: Do not include snoop-filter latency in crossbar occupancy

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This patch ensures that the snoop-filter latency only contributes to
the packet latency, and not to the crossbar throughput/occupancy. In
essence we treat the snoop-filter lookup as pipelined.
This commit is contained in:
Andreas Hansson 2015-09-25 06:45:52 -04:00
parent 40fcb59c54
commit 3bd78a141e
1 changed files with 7 additions and 5 deletions
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12
src/mem/coherent_xbar.cc
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@ -192,11 +192,10 @@ CoherentXBar::recvTimingReq(PacketPtr pkt, PortID slave_port_id)
if (snoopFilter) {
// check with the snoop filter where to forward this packet
auto sf_res = snoopFilter->lookupRequest(pkt, *src_port);
// If SnoopFilter is enabled, the total time required by a packet
// to be delivered through the xbar has to be charged also with
// to lookup latency of the snoop filter (sf_res.second).
// the time required by a packet to be delivered through
// the xbar has to be charged also with to lookup latency
// of the snoop filter
pkt->headerDelay += sf_res.second * clockPeriod();
packetFinishTime += sf_res.second * clockPeriod();
DPRINTF(CoherentXBar, "recvTimingReq: src %s %s 0x%x"\
" SF size: %i lat: %i\n", src_port->name(),
pkt->cmdString(), pkt->getAddr(), sf_res.first.size(),
@ -384,7 +383,10 @@ CoherentXBar::recvTimingSnoopReq(PacketPtr pkt, PortID master_port_id)
if (snoopFilter) {
// let the Snoop Filter work its magic and guide probing
auto sf_res = snoopFilter->lookupSnoop(pkt);
// No timing here: packetFinishTime += sf_res.second * clockPeriod();
// the time required by a packet to be delivered through
// the xbar has to be charged also with to lookup latency
// of the snoop filter
pkt->headerDelay += sf_res.second * clockPeriod();
DPRINTF(CoherentXBar, "recvTimingSnoopReq: src %s %s 0x%x"\
" SF size: %i lat: %i\n", masterPorts[master_port_id]->name(),
pkt->cmdString(), pkt->getAddr(), sf_res.first.size(),