Messages in this thread | | | Date | Thu, 1 Aug 2002 09:09:36 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [rfc] aio-core for 2.5.29 (Re: async-io API registration for 2.5.29) |
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On Thu, 1 Aug 2002, Chris Friesen wrote: > > Now if we had a constant monotonic source of time--say 64-bit nanoseconds since > boot--this wouldn't be a problem.
Well, we do have such a monotonic time sequence already, and that's the one that the kernel always uses internally.
It's called "jiffies64".
However, "jiffies" are not really real time, they are only a "reasonable abstraction thereof", and while they imply ordering ("time_after()" works fine inside the kernel), they do _not_ imply real time.
In other words, there is no way to move from time -> jiffies and back.
But we could certainly export jiffies64 as a "nanosecond-like" thing. All it takes is one 32x64-bit multiply. It won't be "true nanoseconds", but it will be a "reasonable approximation" (ie the rate may be off by several percentage points, since nothing is correcting for it. But the "no correction" is part of the _advantage_ too).
Linus
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