Messages in this thread | | | Subject | Re: Prioritized I/O | Date | Sat, 14 Aug 1999 20:44:43 -0600 | From | Larry McVoy <> |
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Steven Suson writes: > I've been thinking about the discussions on latency, especially in > regards to multilmedia recording, etc. If I/O were prioritized in the > way that CPU utilization is, then this would allow R/T processes to also > take precendence for I/O, thus reducing latency. In addition, this > yields all sorts of benefits for time sensitive I/O. > > Any thoughts? Opinions? Etc.?
I prototyped something like this in SunOS years ago. It was a big win for responsiveness because I used it to make executable pagefaults have higher priority than writes.
It never went in because there are fairness issues - consider a system generating a lot of dirty pages and you are giving reads higher priority. The system grinds to a halt. I never solved that part of the problem.
Anyway, there is an easy way to do this - every operating system has a disk queue with pending disk I/Os. Just turn that into multiple queues.
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