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Efficient Execution of Mixed Application Workloads in a Hard Real-Time Multicore System Marco Paolieri (BSC/UPC) Eduardo Quiñones (BSC) Francisco J. Cazorla (BSC) Mateo Valero (BSC/UPC). RePP Workshop Grenoble, 15 th October. Future Real-Time Systems. - PowerPoint PPT Presentation
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Marco PaolieriRePP WorkshopOctober 15th
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Efficient Execution of Mixed Application Workloads
in a Hard Real-Time Multicore System
Marco Paolieri (BSC/UPC)
Eduardo Quiñones (BSC)
Francisco J. Cazorla (BSC)
Mateo Valero (BSC/UPC)
RePP WorkshopGrenoble, 15th October
Marco PaolieriRePP WorkshopOctober 15th
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Future Real-Time Systems
Current real-time embedded systems require higher performance than provided by current processors
Increasing safety, comfort, number and quality of services
Marco PaolieriRePP WorkshopOctober 15th
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Architecture
What about predictability?What about predictability?
Marco PaolieriRePP WorkshopOctober 15th
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Multicores in RTESs: disadvantages
It is harder to perform WCET analysis for multicore processors than for single-core because of Inter-thread Interferences
Inter-thread interferences accessing shared resources make the execution time vary
Execution time, and so the WCET of a HRT depend on the mixed application workload
WCETa d
Where:
• WCETa WCET est without interferences
• d deadline
• ETa,b ET of a running with b
• ETa,c ET of a running with c
ETa,b ETa,c
deadlinemiss
Is it possible to use multicores to execute mixed application workloads?
Is it possible to use multicores to execute mixed application workloads?
Marco PaolieriRePP WorkshopOctober 15th
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Our Goal
Execute efficiently mixed application workload providing
predictability to HRTs
maximizing performance of NHRTs with the resources not used by HRTs
Marco PaolieriRePP WorkshopOctober 15th
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Regarding HRTs
Our multicore architecture guarantees by design that the maximum delay a request accessing a shared resource may suffer due to inter-thread interferences has an Upper Bound Delay (UBD)
Inter-thread interferences < UBD
Round Robin provides UBD based on the number of requestors
UBD = (NHRT – 1) * LBUS
where LBUS is the latency of the bus and NHRT the total number of HRTs running at the same time
The impact of inter-thread interferences on WCET is up to 40% [Paolieri et al. Hardware Support for WCET Analysis of Multicore Hard Real-Time Systems, ISCA’09]
Marco PaolieriRePP WorkshopOctober 15th
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What about Non Real-Time Tasks?
HRTs are accessing shared resources as soon as they are available, what we call Average-Case Resource Managament (AC-RM)
NHRTs could be starving before accessing shared resources
To execute efficiently a mixed application workload
It is required to maximize the perfomance of NHRTs
Marco PaolieriRePP WorkshopOctober 15th
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Our Proposal
No advantages if executing the HRTs before their WCET
We evaluate a resource management policy, called Worst-Case Resource Management (WC-RM)
Every access to a shared resource from a HRT is stalled by UBD cycles
This forces HRTs to be executed closer to their WCET
It provides performance to NHRTs still guaranteeing that HRTs meet their deadlines
Reducing the variance between average case execution time and WCET performances of NHRTs can increase
Marco PaolieriRePP WorkshopOctober 15th
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How It Works
1.041.011.031.061.051.051.041.051.061.051.04
Marco PaolieriRePP WorkshopOctober 15th
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Experimental Setup
As HRT benchmarks we use:
A real HRT application provided by Honeywell
3D collision avoidance algorithm
EEMBC Automotive
As NHRT benchmarks we use
MediaBench, MiBench, SPEC CPU 2006
Marco PaolieriRePP WorkshopOctober 15th
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Results
Baseline: throughput of NHRTs using the AC-RM
1
Marco PaolieriRePP WorkshopOctober 15th
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Effect on HRTs
Baseline: Performance of HRTs using AC-RM
WC-RM is between 1 and 2 % close to its WCET estimation
1
Marco PaolieriRePP WorkshopOctober 15th
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Conclusions
Our architecture is designed from a WCET point of view
It implements a hardware shared-resource management policy, called Worst-Case Resource Management (WC-RM)
It improves the performance level of NHRTs when running in a mixed application workload
Marco PaolieriRePP WorkshopOctober 15th
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Thanks for the attention!