PR SM

1. PR SM Versailles Saint Quentin University Laboratory National Scientific research center File system Cache memory Process Memory Disk cache Disk I/O Generator Simulation Tool I/O request FastIO 4 File system driver Storage Device driver Cache manager Page fault Storage Device Virtual memory manager Empirical I/O Parameter Extraction • File system cache -> process memory throughput (1) • Disk cache -> process memory throughput (2) • Seek times • Track sizes (zoning) • Disk cache segment size and number • Disk cache algorithms Study the periodicity to find track size Measuring throughputs • Cache segment size Read block of size T from disk Re-read that block: if entirely loaded from the disk cache -> segment size ≥T, increment T else decrement T Empty the cache Seek times Measuring Tools 1 2 Systematic global performance measuring tool Automatic parameter extraction 3 Storage architecture I/O sequence strategy defined by the user or real workload traces Performance of the storage system for read/write operation Behavior of the storage system for the specified I/O strategy A Parameter Extraction Tool for Windows I/O System Characterization MASCOTS 2004 JalilBOUKHOBZA The Problem Statement • I/Os are critical. • Windows OS Vaguely documented • Sources are not available • Poorly studied in academic research • Hardware manufacturer’s documentation not sufficient for completely • understanding a given I/O system and simulating it. The Objectives • Understanding I/O flow and Performance in Windows systems. • Making possible accurate simulations of the Windows I/O subsystem: • From the application -> Disk mechanical movements Contributions • Windows I/O performance measurement tool : Measure I/O performance of a given architecture on a Windows OS (2000, XP, 2003) • Empirical I/O parameters extraction tool : • Get the parameters defining the I/O subsystem to: • Understand the resultant performance • Build accurate simulations 2 1 Windows I/O Performance Measurements • Windows file access modes (Win32 CreateFile()) • Normal, sequential, random, no buffer, write through • Request sizes • Sequential / Random (accesses) Results: • I/O throughput • Response times Example of execution Configuration: Read transfer rates and response times 4 3 Example: 1 2 Using flags of the CreateFile() function • Disk cache updating algorithms • Generally simple algorithms (LRU, FIFO, LFU, etc.) that can be tested once the segment size known by issuing different read block sequences and then re-read the blocks to see which one is accessed from the disk (and so has been ejected from the cache). Per request response time 5 6 Conclusions • A Windows dedicated I/O performance measurement tool taking into account the • different access modes (using different prefetching algorithms for read / write operations). • Very easy to use tool to get I/O parameters. The extracted parameters allow to run • accurate simulations less then 4% variation compared to real measures for response • times and throughputs. Under development • Allowing asynchronous file accesses • Injecting inter arrival times • More control on request sequentiality • Testing more architectures • References • Some Studies on Windows I/Os • [1] E.Riedel, C.VanIngen, J.Gray “A performance study of sequential I/O on WindowsNT4”, 2nd USENIX WindowsNT Symposium, Seattle, • WA, 1998. • [2] L.Chung, J.Gray, B.Worthington, R.Horst, Windows2000 disk I/O performance, Technical report MS-TR-2000-55, Microsoft Research, 2000. • [3] J. Boukhobza, C. Timsit, “On Windows File Access modes: a Performance Study”, to appear in the proceeding of WISICT2005, • Cape Town, South Africa, January 2005. • About Windows internals • [4] D.A.Solomon, M.E.Russinovich, Inside Windows2000, Redmond, Washington, Microsoft Press, 2000. • Caching policies • [5] N.C Burnett, J. Bent, A.C. Arpaci-Dusseau, R.H. Arpaci-Dusseau, “Exploiting Gray-Box knowledge of Buffer-cache management”, • proceeding of USENIX 2002 Annual Technical conference, Monterey, California, USA, June 2002. • Windows I/O simulations • [6] J. Boukhobza, C. Timsit, “An I/O Simulator for Windows Systems”, to appear in ESMc2004 proceeding, Paris, France, October 2004. 7 8 PRiSM Laboratory, Versailles Saint Quentin University 45 Etats Unis Avenue – 78 035 Versailles Cedex E-mail : jalil.boukhobza@prism.uvsq.fr