Interprocessor Communication : Towards Cache Integrated Network ...

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Institute of Computer Science (ICS) – member of HiPEAC. Foundation for Research ... Configure the degree of cache asso
Interprocessor Communication : Towards Cache Integrated Network Interfaces Vassilis Papaefstathiou and Michael Papamichael Foundation for Research and Technology-Hellas (FORTH) Institute of Computer Science (ICS) – member of HiPEAC Computer Architecture and VLSI Systems Laboratory (CARV) Work funded by SARC

Motivation and Context ♦ Many on-chip cores available today (CMPs) – – – –

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Key scalability issue : efficient interprocessor communication Network-on-Chip (NoC) for the interconnection Memory resources in every tile used as L1 or L2 cache NoC interface in every tile Æ low cost to afford



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Network-on-Chip NI

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Cache Integrated Network Interfaces ♦ Tightly-coupled processor - network architecture

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– Processor and NI share local memory Æ lightweight NI – Allocation of memory blocks for NI use ƒ coarse or fine-grain block allocation (cache-line) – Fast and low latency mechanism for explicit messaging ƒ stores (send) and loads (receive) – Integrate NI mechanisms into the cache controller ƒ transmission similar to cache write-back ƒ reception similar to cache miss

Local Memory & Cache Controller

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Network-on-Chip

♦ Desired communication primitives

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– RDMA for bulk transfers ƒ post descriptors in cache-lines – Queues for small explicit transfers ƒ specify destination, size and payload ƒ send queues ( one-to-many ) ƒ receive queues ( many-to-one )

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1ÆN Local Memory & Cache Controller

Cache Line

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NI Queue

Runtime Configurable Memory Resources NI

♦ Applications configure the memory type ♦ Computation intensive applications

– Configure the degree of cache associativity

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♦ Communication intensive applications – Fine grain allocation of blocks for NI

Configurable HW

– Diverse applications Æ different memory requirements

♦ Real-time embedded applications – Configure as addressable local store - scratchpad ƒ predictable performance

Local Memory Resources

Cache Line

NI Queue

Scratchpad

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