Marco Paolieri RePP Workshop October 15 th 1 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

Marco Paolieri RePP Workshop October 15 th 2 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 Paolieri RePP Workshop October 15 th 3 Architecture What about predictability?

Marco Paolieri RePP Workshop October 15 th 4 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 WCET a d Where: WCET a WCET est without interferences ddeadline ET a,b ET of a running with b ET a,c ET of a running with c ET a,b ET a,c deadline miss Is it possible to use multicores to execute mixed application workloads?

Marco Paolieri RePP Workshop October 15 th 5 Our Goal  Execute efficiently mixed application workload providing  predictability to HRTs  maximizing performance of NHRTs with the resources not used by HRTs

Marco Paolieri RePP Workshop October 15 th 6 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 = (N HRT – 1) * L BUS where L BUS is the latency of the bus and N HRT 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 Paolieri RePP Workshop October 15 th 7 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 Paolieri RePP Workshop October 15 th 8 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 Paolieri RePP Workshop October 15 th 9 How It Works

Marco Paolieri RePP Workshop October 15 th 10 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 Paolieri RePP Workshop October 15 th 11 Results  Baseline: throughput of NHRTs using the AC-RM 1

Marco Paolieri RePP Workshop October 15 th 12 Effect on HRTs  Baseline: Performance of HRTs using AC-RM  WC-RM is between 1 and 2 % close to its WCET estimation 1

Marco Paolieri RePP Workshop October 15 th 13 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 Paolieri RePP Workshop October 15 th 14 Thanks for the attention!