README.txt revision 11666:10d59d546ea2
1README for Garnet2.0 2Written By: Tushar Krishna (tushar@ece.gatech.edu) 3Last Updated: Jul 9, 2016 4------------------------------------------------------- 5 6Garnet Network Parameters and Setup: 7- GarnetNetwork.py 8 * defaults can be overwritten from command line (see configs/network/Network.py) 9- GarnetNetwork.hh/cc 10 * sets up the routers and links 11 * collects stats 12 13 14CODE FLOW 15- NetworkInterface.cc::wakeup() 16 * Every NI connected to one coherence protocol controller on one end, and one router on the other. 17 * receives messages from coherence protocol buffer in appropriate vnet and converts them into network packets and sends them into the network. 18 * garnet2.0 adds the ability to capture a network trace at this point. 19 * receives flits from the network, extracts the protocol message and sends it to the coherence protocol buffer in appropriate vnet. 20 * manages flow-control (i.e., credits) with its attached router. 21 * The consuming flit/credit output link of the NI is put in the global event queue with a timestamp set to next cycle. 22 The eventqueue calls the wakeup function in the consumer. 23 24- NetworkLink.cc::wakeup() 25 * receives flits from NI/router and sends it to NI/router after m_latency cycles delay 26 * Default latency value for every link can be set from command line (see configs/network/Network.py) 27 * Per link latency can be overwritten in the topology file 28 * The consumer of the link (NI/router) is put in the global event queue with a timestamp set after m_latency cycles. 29 The eventqueue calls the wakeup function in the consumer. 30 31- Router.cc::wakeup() 32 * Loop through all InputUnits and call their wakeup() 33 * Loop through all OutputUnits and call their wakeup() 34 * Call SwitchAllocator's wakeup() 35 * Call CrossbarSwitch's wakeup() 36 * The router's wakeup function is called whenever any of its modules (InputUnit, OutputUnit, SwitchAllocator, CrossbarSwitch) have 37 a ready flit/credit to act upon this cycle. 38 39- InputUnit.cc::wakeup() 40 * Read input flit from upstream router if it is ready for this cycle 41 * For HEAD/HEAD_TAIL flits, perform route computation, and update route in the VC. 42 * Buffer the flit for (m_latency - 1) cycles and mark it valid for SwitchAllocation starting that cycle. 43 * Default latency for every router can be set from command line (see configs/network/Network.py) 44 * Per router latency (i.e., num pipeline stages) can be set in the topology file 45 46- OutputUnit.cc::wakeup() 47 * Read input credit from downstream router if it is ready for this cycle 48 * Increment the credit in the appropriate output VC state. 49 * Mark output VC as free if the credit carries is_free_signal as true 50 51- SwitchAllocator.cc::wakeup() 52 * Note: SwitchAllocator performs VC arbitration and selection within it. 53 * SA-I (or SA-i): Loop through all input VCs at every input port, and select one in a round robin manner. 54 * For HEAD/HEAD_TAIL flits only select an input VC whose output port has at least one free output VC. 55 * For BODY/TAIL flits, only select an input VC that has credits in its output VC. 56 * Place a request for the output port from this VC. 57 * 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. 58 * For HEAD/HEAD_TAIL flits, perform outvc allocation (i.e., select a free VC from the output port). 59 * For BODY/TAIL flits, decrement a credit in the output vc. 60 * Read the flit out from the input VC, and send it to the CrossbarSwitch 61 * Send a increment_credit signal to the upstream router for this input VC. 62 * for HEAD_TAIL/TAIL flits, mark is_free_signal as true in the credit. 63 * The input unit sends the credit out on the credit link to the upstream router. 64 * Reschedule the Router to wakeup next cycle for any flits ready for SA next cycle. 65 66- CrossbarSwitch.cc::wakeup() 67 * Loop through all input ports, and send the winning flit out of its output port onto the output link. 68 * The consuming flit output link of the router is put in the global event queue with a timestamp set to next cycle. 69 The eventqueue calls the wakeup function in the consumer. 70 71 72