1. PR SM Laboratory A Parameter Extraction Tool for Windows I/O System Characterization Versailles Saint Quentin University National Scientific research center Jalil BOUKHOBZA 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 :  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 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 File system driver Storage Device driver Storage Device Cache manager Virtual memory manager I/O request FastIO Page fault Read transfer rates and response times Example of execution Configuration: 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 Process Memory File system Cache memory Disk Disk cache Measuring throughputs 1 2 Example: 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. Seek times Study the periodicity to find track size Per request response time 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 Systematic global performance measuring tool Automatic parameter extraction Storage architecture I/O sequence strategy defined by the user or real workload traces Measuring Tools Behavior of the storage system for the specified I/O strategy Performance of the storage system for read/write operation I/O Generator Simulation Tool 12 3 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). Using flags of the CreateFile() function 1 2 3 4 5 6 78 4 MASCOTS 2004