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Hand-waving about a phased sleepHand-waving about a phased sleepPosted Jan 7, 2009 17:55 UTC (Wed) by johntb86 (subscriber, #53897)In reply to: Hand-waving about a phased sleep by BrucePerens Parent article: Btrfs aims for the mainline
That's an interesting idea, but as far as I know to wake up the processor you'd need an IPI, so it's not exactly cheap. You'd also need to create a timer interrupt to wake up the processor if it's not woken up by some other method, so this could become a pretty expensive way to have the processor do no work for a while.
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Hand-waving about a phased sleep Posted Jan 7, 2009 18:26 UTC (Wed) by BrucePerens (guest, #2510) [Link] Perhaps we need hardware support to make this work properly. A timed halt instruction, or a low-level atomic primitive that can wake a processor waiting for an address.
Hand-waving about a phased sleep Posted Jan 7, 2009 21:29 UTC (Wed) by jlokier (guest, #52227) [Link]
x86 does have a primitive to wait on an address: monitor/mwait.
It waits until the monitored location is modified by another processor.
I read that it's a bit slow for this sort of thing.
In principle, if it were fast (and it could be with MESI caches),
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