* Peter Zijlstra <[email protected]> wrote:
> On Thu, 2012-10-25 at 15:26 -0700, Linus Torvalds wrote:
> > it's the *rest* of the "u128" math I really object to. I also wonder
> > about the u64xu64 math case for SCHED_DEADLINE, because I assume that
> > it doesn't actually end up using the 128-bit result in that form, but
> > scales it down again some way?
>
> No, it does a compare on two u128, so it doesn't loose any
> precision. If it were to scale down again and loose precision
> I'd agree with you that introducing the u128 stuff is
> pointless.
>
> The point is (as mentioned in the comments below) overflowing
> an actual u64 is rare, however since some of this
> (specifically the dl_{runtime,deadline} parameters) is user
> specified, we have to assume we will overflow.
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.
Thanks,
Ingo
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