Exploiting heterogeneous manycores on sequential code

Bharath Narasimha Swamy 1
1 ALF - Amdahl's Law is Forever
Inria Rennes – Bretagne Atlantique , IRISA-D3 - ARCHITECTURE
Abstract : Heterogeneous Many Cores (HMC) architectures that mix many simple/small cores with a few complex/large cores are emerging as a design alternative that can provide both fast sequential performance for single threaded workloads and power-efficient execution for through-put oriented parallel workloads. The availability of many small cores in a HMC presents an opportunity to utilize them as low-power helper cores to accelerate memory-intensive sequential programs mapped to a large core. However, the latency overhead of accessing small cores in a loosely coupled system limits their utility as helper cores. Also, it is not clear if small cores can execute helper threads sufficiently in advance to benefit applications running on a larger, much powerful, core. In this thesis, we present a hardware/software framework called core-tethering to support efficient helper threading on heterogeneous many-cores. Core-tethering provides a co-processor like interface to the small cores that (a) enables a large core to directly initiate and control helper execution on the helper core and (b) allows efficient transfer of execution context between the cores, thereby reducing the performance overhead of accessing small cores for helper execution. Our evaluation on a set of memory intensive programs chosen from the standard benchmark suites show that, helper threads using moderately sized small cores can significantly accelerate a larger core compared to using a hardware prefetcher alone. We also find that a small core provides a good trade-off against using an equivalent large core to run helper threads in a HMC. In summary, despite the latency overheads of accessing prefetched cache lines from the shared L3 cache, helper thread based prefetching on small cores looks as a promising way to improve single thread performance on memory intensive workloads in HMC architectures.
Keywords : Microprocessor
Document type :
Theses
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https://hal.inria.fr/tel-01126807
Contributor : Narasimha Swamy Bharath <>
Submitted on : Tuesday, March 17, 2015 - 4:01:47 AM
Last modification on : Friday, January 11, 2019 - 1:53:05 PM
Long-term archiving on : Thursday, June 18, 2015 - 10:06:21 AM

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  • HAL Id : tel-01126807, version 1

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Bharath Narasimha Swamy. Exploiting heterogeneous manycores on sequential code. Computer Science [cs]. UNIVERSITE DE RENNES 1, 2015. English. ⟨tel-01126807⟩

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