Hierarchical Real-time Garbage Collection

Transcription

1 Hierarchical Real-time Garbage Collection Filip Pizlo Antony L. Hosking Jan Vitek Presenter: Petur Olsen October 4, 2007

2 The general idea Introduction The Article The Authors 2/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

3 The Article The Authors The Article Published ACM SIGPLAN/SIGBED 2007 Conference on Languages, Compilers, and Tools for Embedded Systems (LCTES 07) ACM SIGPLAN Notices Volume 42, Issue 7 Contributions New garbage collector Hard real-time Increased predictability Better performance Mixing hard and soft real-time garbage collectors 3/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

4 The Article The Authors The Authors Filip Pizlo Ph.D. student at Secure Software Systems Lab at Purdue University Garbage collection, real-time systems, programming languages Antony Hosking Associate Professor at Purdue University Secure Software Systems Lab DaCapo Project - compiler analysis, optimization, memory management 4/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

5 The Article The Authors The Authors Jan Vitek Associate Professor at Purdue University Founding Member of the Secure Software Systems Lab Programming languages and virtual machines with applications to real-time embedded systems All three Developers of OVM - Customizable open source Real-time Java Virtual Machine. 5/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

6 Outline Introduction The Article The Authors 1 Hierarchical Real-Time Garbage Collection 2 3 6/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

7 Garbage Collectors Correctness Invariants Hierarchical Real-Time Garbage Collection (HRTGC) Heaplets structured hierarchically Static size Several threads per heaplet One (specialized) garbage collector per heaplet Based on RTSJ Cross heaplet references 7/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

8 Heaplets Introduction Garbage Collectors Correctness Invariants 8/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

9 References Introduction Garbage Collectors Correctness Invariants 9/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

10 References Introduction Garbage Collectors Correctness Invariants 10/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

11 References Introduction Garbage Collectors Correctness Invariants 11/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

12 Garbage Collectors Correctness Invariants Terminology Terms Roots Snapshot at beginning Mark and sweep Tri-color invariant Scanning Tracing Sweeping 12/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

13 Garbage Collectors Correctness Invariants Garbage Collectors Types Heaplet collector Root collector Cycle collector 13/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

14 Garbage Collectors Correctness Invariants Heaplet collector Scans all thread stacks (atomic) Scans descendant heaplets Scans cross set Traces current heaplet Sweeps current heaplet 14/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

15 Garbage Collectors Correctness Invariants Root collector Scans all thread stacks (atomic) Scans static fields Scans descendant heaplets Traces current heaplet Sweeps current heaplet 15/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

16 Garbage Collectors Correctness Invariants Cycle collector Scans all thread stacks (atomic) Scans static fields Traces all heaplets Sweeps cross-set 16/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

17 Garbage Collectors Correctness Invariants Invariants Interference Non-moving Mutator-collector interference Collector-collector interference 17/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

18 Collector-collector interference Garbage Collectors Correctness Invariants 18/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

19 Garbage Collectors Correctness Invariants Collector-collector interference Scenarios Trace first - no problem Delete first - mark objects Delete during scan - abort delete 19/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

20 Setup Results Machine 3.8 GHz Pentium 4 4 GB physical memory Ubuntu Linux Implementation Modified OVM 227 mtrt as background noise Large footprint and high allocation Runs in root heaplet 20/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

21 Setup Results Projects Collision Detection Simulates aircraft collision detection 41Kloc RTSJ program Two sibling heaplets Minimal rewrite RTZen Multithreaded real-time CORBA ORB 202Kloc RTSJ program One heaplet None refactoring 21/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

22 Setup Results Benchmarks Worst-case Response time RTZen improves 15% with HRTGC CD improves 26% with HRTGC 22/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

23 Setup Results Benchmarks Minimum Mutator Utilization RTZen max utilization of 97% with HRTGC RTZen max utilization of 35% with RTGC CD max utilization of 92% with HRTGC CD max utilization of 51% with RTGC 23/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

24 Setup Results Benchmarks Footprint RTGC is 65% worse RTGC can be better by significantly lowering response time 24/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

25 Setup Results Benchmarks Throughput Several test in one heap Measures the raw overhead of the HRTGC HRTGC is % worse than RTGC 25/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

26 Hierarchical Real-Time Garbage Collection Increased predictability Better performance (Hard) real-time 26/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

27 The article Written for insiders Too technical 27/28 Pizlo, Hosking, Vitek Hierarchical Real-time Garbage Collection

28 Questions?