| Date | Fri, 26 Oct 2012 11:42:07 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 01/16] math128: Introduce various 128bit primitives |
| |
* Peter Zijlstra <peterz@infradead.org> wrote:
> On Fri, 2012-10-26 at 11:24 +0200, Ingo Molnar wrote: > > > So can we control this by restricting the users and avoiding > > the overflow? > > > > A 2^64 result should be a *huge* amount of space already for > > just about anything. > > I _think_ something like: dl_runtime * dl_deadline < U64_MAX, > might do that. The question is, is this constraint usable? > Simplified that boils down to about 4 seconds each, which > sounds pretty much ok for most people -- but such statements > usually come back to bite you (640kb anybody...).
We could constrain the precision, not the maximum value.
Having a 4 seconds hard limit is one thing, only having 10 nsecs precision at 40 seconds is another.
Then the introduction of 128 bit math would be purely optional and would address *that* limitation of precision, and only that limitation. That way we could gladly skip 128 bit math.
Thanks,
Ingo
|