Aérgia: Exploiting packet latency slack in on-chip networks

Reetuparna Das, Onur Mutlu, Thomas Moscibroda, Chita R. Das

Research output: Chapter in Book/Report/Conference proceedingConference contribution

102 Scopus citations


Traditional Network-on-Chips (NoCs) employ simple arbitration strategies, such as round-robin or oldest-first, to decide which packets should be prioritized in the network. This is suboptimal since different packets can have very different effects on system performance due to, e.g., different level of memory-level parallelism (MLP) of applications. Certain packets may be performance-critical because they cause the processor to stall, whereas others may be delayed for a number of cycles with no effect on application-level performance as their latencies are hidden by other outstanding packets' latencies. In this paper, we define slack as a key measure that characterizes the relative importance of a packet. Specifically, the slack of a packet is the number of cycles the packet can be delayed in the network with no effect on execution time. This paper proposes new router prioritization policies that exploit the available slack of interfering packets in order to accelerate performance-critical packets and thus improve overall system performance. When two packets interfere with each other in a router, the packet with the lower slack value is prioritized. We describe mechanisms to estimate slack, prevent starvation, and combine slack-based prioritization with other recently proposed application-aware prioritization mechanisms. We evaluate slack-based prioritization policies on a 64-core CMP with an 8x8 mesh NoC using a suite of 35 diverse applications. For a representative set of case studies, our proposed policy increases average system throughput by 21.0% over the commonlyused round-robin policy. Averaged over 56 randomly-generated multiprogrammed workload mixes, the proposed policy improves system throughput by 10.3%, while also reducing application-level unfairness by 30.8%.

Original languageEnglish (US)
Title of host publicationISCA 2010 - The 37th Annual International Symposium on Computer Architecture, Conference Proceedings
Number of pages11
StatePublished - 2010
Event37th International Symposium on Computer Architecture, ISCA 2010 - Saint-Malo, France
Duration: Jun 19 2010Jun 23 2010

Publication series

NameProceedings - International Symposium on Computer Architecture
ISSN (Print)1063-6897


Other37th International Symposium on Computer Architecture, ISCA 2010

All Science Journal Classification (ASJC) codes

  • Hardware and Architecture


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