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diff --git a/src/mem/ruby/network/garnet2.0/README.txt b/src/mem/ruby/network/garnet2.0/README.txt new file mode 100644 index 000000000..817b1d48d --- /dev/null +++ b/src/mem/ruby/network/garnet2.0/README.txt @@ -0,0 +1,71 @@ +README for Garnet2.0 +Written By: Tushar Krishna (tushar@ece.gatech.edu) +Last Updated: Jul 9, 2016 +------------------------------------------------------- + +Garnet Network Parameters and Setup: +- GarnetNetwork.py + * defaults can be overwritten from command line (see configs/network/Network.py) +- GarnetNetwork.hh/cc + * sets up the routers and links + * collects stats + + +CODE FLOW +- NetworkInterface.cc::wakeup() + * Every NI connected to one coherence protocol controller on one end, and one router on the other. + * receives messages from coherence protocol buffer in appropriate vnet and converts them into network packets and sends them into the network. + * garnet2.0 adds the ability to capture a network trace at this point. + * receives flits from the network, extracts the protocol message and sends it to the coherence protocol buffer in appropriate vnet. + * manages flow-control (i.e., credits) with its attached router. + * The consuming flit/credit output link of the NI is put in the global event queue with a timestamp set to next cycle. + The eventqueue calls the wakeup function in the consumer. + +- NetworkLink.cc::wakeup() + * receives flits from NI/router and sends it to NI/router after m_latency cycles delay + * Default latency value for every link can be set from command line (see configs/network/Network.py) + * Per link latency can be overwritten in the topology file + * The consumer of the link (NI/router) is put in the global event queue with a timestamp set after m_latency cycles. + The eventqueue calls the wakeup function in the consumer. + +- Router.cc::wakeup() + * Loop through all InputUnits and call their wakeup() + * Loop through all OutputUnits and call their wakeup() + * Call SwitchAllocator's wakeup() + * Call CrossbarSwitch's wakeup() + * The router's wakeup function is called whenever any of its modules (InputUnit, OutputUnit, SwitchAllocator, CrossbarSwitch) have + a ready flit/credit to act upon this cycle. + +- InputUnit.cc::wakeup() + * Read input flit from upstream router if it is ready for this cycle + * For HEAD/HEAD_TAIL flits, perform route computation, and update route in the VC. + * Buffer the flit for (m_latency - 1) cycles and mark it valid for SwitchAllocation starting that cycle. + * Default latency for every router can be set from command line (see configs/network/Network.py) + * Per router latency (i.e., num pipeline stages) can be set in the topology file + +- OutputUnit.cc::wakeup() + * Read input credit from downstream router if it is ready for this cycle + * Increment the credit in the appropriate output VC state. + * Mark output VC as free if the credit carries is_free_signal as true + +- SwitchAllocator.cc::wakeup() + * Note: SwitchAllocator performs VC arbitration and selection within it. + * SA-I (or SA-i): Loop through all input VCs at every input port, and select one in a round robin manner. + * For HEAD/HEAD_TAIL flits only select an input VC whose output port has at least one free output VC. + * For BODY/TAIL flits, only select an input VC that has credits in its output VC. + * Place a request for the output port from this VC. + * SA-II (or SA-o): Loop through all output ports, and select one input VC (that placed a request during SA-I) as the winner for this output port in a round robin manner. + * For HEAD/HEAD_TAIL flits, perform outvc allocation (i.e., select a free VC from the output port). + * For BODY/TAIL flits, decrement a credit in the output vc. + * Read the flit out from the input VC, and send it to the CrossbarSwitch + * Send a increment_credit signal to the upstream router for this input VC. + * for HEAD_TAIL/TAIL flits, mark is_free_signal as true in the credit. + * The input unit sends the credit out on the credit link to the upstream router. + * Reschedule the Router to wakeup next cycle for any flits ready for SA next cycle. + +- CrossbarSwitch.cc::wakeup() + * Loop through all input ports, and send the winning flit out of its output port onto the output link. + * The consuming flit output link of the router is put in the global event queue with a timestamp set to next cycle. + The eventqueue calls the wakeup function in the consumer. + + |