Messages in this thread | | | Date | Tue, 13 Jul 1999 13:32:27 -0400 (EDT) | From | Chuck Lever <> | Subject | Re: [RFC] - Some notions that I would like comments on |
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On Mon, 12 Jul 1999 cd_smith@ou.edu wrote: > With the caveat that I didn't write the original message (so I may be the > one without a clue here) I think a few people are missing the point on > this speculative I/O thing. I don't know that it's a good idea, but it's > at least worth understanding and evaluating. As I see it, the big > difference between "speculative" I/O and asynchronous I/O is the > interface. Speculative I/O would appear to be a blocking I/O call, but as > soon as it queued the I/O request, it would return. The result page would > be marked as unreadable and unwriteable, and the actual I/O blocking would > be done on a page fault.
there's a good paper related to this published in the OSDI '99 proceedings. see:
Chang, F., Gibson, G., "Automatic I/O Hint Generation through Speculative Execution," Proceedings of the Third Symposium on Operating Systems Design and Implementation, pp. 1-14, February 1999.
the authors used speculative execution during I/O waits to predict future read requests instead of the method you described. their conclusion was that were good gains from speculative execution, but the technique requires significant O/S complexity.
- Chuck Lever -- corporate: <chuckl@netscape.com> personal: <chucklever@netscape.net> or <cel@monkey.org>
The Linux Scalability project: http://www.citi.umich.edu/projects/linux-scalability/
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