CSE 291 a Interconnection Networks Lecture 12 Deadlock

CSE 291 -a Interconnection Networks Lecture 12: Deadlock Avoidance (Cont’d) Router February 28, 2007 Prof. Chung-Kuan Cheng CSE Dept, UC San Diego Winter 2007 Transcribed by Yi Zhu

Topics o Deadlock avoidance n n Restricted physical route (lecture 10) Resource classes o o n o Distance classes Dateline (ring) Duato’s protocol Router Architecture

Distance Classes o o #classes >= diameter of network At source, we inject packets into resource of class 0 At each hop, the packet of class i acquires a resource of class i+1 Use min routing

Dateline (Ring) o o There are two classes A dateline cuts the ring into a string At source, we inject packets into resources of class 0 Packets remain in the same class, but jump to class 1 when crossing the dateline

Dateline (Ring)

Duato’s Protocol for Deadlock-Free Adaptive Algorithm o o The underlying network is deadlockfree. The routing relation is R 1: escape routing Create new virtual resources and routing relation Rc Rc -> R 1 works as injection at the node. R 1 -> Rc not allowed

Router Architecture state Physical channel buffer

Virtual Channel State o o Virtual channel state fields: 5 -vector GROPC G: Global state n n n o o I (idle), R (routing) V (waiting for VC) A (active) C (waiting for credits) R: Route, output port R for the packet O: Output VC, output VC O of port R

Virtual Channel State (Cont’d) o o P: Pointers, flit head and flit tail pointers into the input buffer C: Credit count, #credits C for VC O of port R