---------- Title Kernel-Supported Speculative Process Execution for Transparent File System Prefetching CMU 15-712 Software Systems
Authors Ted Pham and Robert Watson Date May 7, 1999 Abstract This paper explores the feasibility of an operating system kernel performing speculative execution of user processes during system idle time to generate file system prefetches. We discuss the implementation, and how the use of existing FreeBSD kernel primitives may be leveraged to provide this through minimal modifications to the underlying operating system. We evaluate the effectiveness of the technique, and improvements that would allow us to realize the potential performance increase. URL http://www.watson.org/~robert/15-712/project/ ---------- We're still continuing work on this, and have not had a chance to do a full evaluation or wring all of the bugs out. However, I thought people might be interested in taking a look. Our source code will be available in a month or so once we've had a chance to fix a few more things up. This work is based on a paper by F Chang, "Automatic I/O Hint Generation through Speculative Execution", which appeared in Proceedings of the 3rd Symposium on Operating Systems Design and Implementation, February 1999. The basic idea was to generate file system prefetches based on a speculative thread that executed the code ahead of time, and tried to guess what reads would occur. They did this by performing a binary modification to the base program to create and maintain the thread. We wondered if it would not be more efficient and general to implement this in the OS kernel, and did so based on 4.0-CURRENT of FreeBSD (around May). What they had and what we did not have was RAID disk arrays to run their code against: they had far disk bandwidth than we did, although presumably around the same latency. The paper is not great, as it was largely written extremely early in the morning, but I think it gets across the design goals and intent. Once we've revamped the code a little and gotten it to work a bit better, presumably a published paper will turn up somewhere. Robert N M Watson rob...@fledge.watson.org http://www.watson.org/~robert/ PGP key fingerprint: AF B5 5F FF A6 4A 79 37 ED 5F 55 E9 58 04 6A B1 TIS Labs at Network Associates, Computing Laboratory at Cambridge University Safeport Network Services To Unsubscribe: send mail to majord...@freebsd.org with "unsubscribe freebsd-hackers" in the body of the message
