From d35dd71ab4ac44a79ac22dca82277a43cd59f3c6 Mon Sep 17 00:00:00 2001 From: Marco Balboni Date: Mon, 2 Mar 2015 04:00:46 -0500 Subject: mem: Add crossbar latencies This patch introduces latencies in crossbar that were neglected before. In particular, it adds three parameters in crossbar model: front_end_latency, forward_latency, and response_latency. Along with these parameters, three corresponding members are added: frontEndLatency, forwardLatency, and responseLatency. The coherent crossbar has an additional snoop_response_latency. The latency of the request path through the xbar is set as --> frontEndLatency + forwardLatency In case the snoop filter is enabled, the request path latency is charged also by look-up latency of the snoop filter. --> frontEndLatency + SF(lookupLatency) + forwardLatency. The latency of the response path through the xbar is set instead as --> responseLatency. In case of snoop response, if the response is treated as a normal response the latency associated is again --> responseLatency; If instead it is forwarded as snoop response we add an additional variable + snoopResponseLatency and the latency associated is --> snoopResponseLatency; Furthermore, this patch lets the crossbar progress on the next clock edge after an unused retry, changing the time the crossbar considers itself busy after sending a retry that was not acted upon. --- src/mem/xbar.hh | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'src/mem/xbar.hh') diff --git a/src/mem/xbar.hh b/src/mem/xbar.hh index f51b08da2..ed678d9d0 100644 --- a/src/mem/xbar.hh +++ b/src/mem/xbar.hh @@ -309,8 +309,15 @@ class BaseXBar : public MemObject { retry_port->sendRetrySnoopResp(); } }; - /** cycles of overhead per transaction */ - const Cycles headerCycles; + /** + * Cycles of front-end pipeline including the delay to accept the request + * and to decode the address. + */ + const Cycles frontendLatency; + /** Cycles of forward latency */ + const Cycles forwardLatency; + /** Cycles of response latency */ + const Cycles responseLatency; /** the width of the xbar in bytes */ const uint32_t width; @@ -404,8 +411,11 @@ class BaseXBar : public MemObject * headerDelay and payloadDelay fields of the packet * object with the relative number of ticks required to transmit * the header and the payload, respectively. + * + * @param pkt Packet to populate with timings + * @param header_delay Header delay to be added */ - void calcPacketTiming(PacketPtr pkt); + void calcPacketTiming(PacketPtr pkt, Tick header_delay); /** * Remember for each of the master ports of the crossbar if we got -- cgit v1.2.3