chapter5-m3-ziavras

Inval req to sharer 3a in req val to sharer md 4a

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Unformatted text preview: eality is much harder; – must also avoid deadlock when running out of buffers in network (see Appendix E: Interconnection Networks) • Optimizations: – read miss or write miss in Exclusive » send data directly to requestor from owner vs. 1st to memory and then from memory to requestor 39 Basic Directory Transactions: An Alternative Requestor Requestor 1. P A C Dir ectorynode for block M/D 3. Read req. to o wner 2. Reply with with owner identity A C 3b . Inval. req. to sharer 3a. In req. val. to sharer M/D 4a. Data Reply Dir ectory ode n 4b . Inval. ack 4a. 4a. Inval. ack 4b. Revision message to directory P P C C C A P 2. C Reply with sharers identity A M/D M/D P A P RdEx request to directory di P Read request to directory C 1. M/D Node with dirtycop cop y (a) Read miss to a block in dirty state A M/D Sharr e A M/D Sharr e (b)Write miss to a block with tw o sharers 40 Example Directory Protocol (1st Read) D D: Dirty S; Shared U: Uncached Uncached vA: virtual Address pA: physical Address Read pA S P1: pA R/reply Dir ctrl M U E E S $ P1 S $ P2 R/req I ld vA -> rd pA I 41 Example Directory Protocol (Read Share) D P1: pA R/_ S P2: pA R/reply Dir ctrl M U E R/_ E S $ P1 R/_ S R/req I $ P2 R/req ld vA -> rd pA I ld vA -> rd pA 42 Example Directory Protocol (Wr to shared) D RX/invalidate&reply P1: pA EX R/_ S R/reply P2: pA M Dir ctrl U Inv ACK reply xD(pA) Invalidate pA Read_to_update pA W/_ E W/req E E W/req E R/_ S $ P1 R/req Inv/_ I R/_ S P2 R/req Inv/_ s...
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