Re: [PATCH] tcp_cubic: use 32 bit math

[Stephen Hemminger]

David Miller wrote:
> From: Stephen Hemminger <shemminger@xxxxxxxxxxxxxxxxxxxx>
> Date: Wed, 7 Mar 2007 17:07:31 -0800
>
>   
> > The basic calculation has to be done in 32 bits to avoid
> > doing 64 bit divide by 3. The value x is only 22bits max
> > so only need full 64 bits only for x^2.
> >
> > Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxxxxxxxxxxxxxx>
> >     
>
> Applied, thanks Stephen.
>
> What about Willy Tarreau's supposedly even faster variant?
> Or does this incorporate that set of improvements?
>   
That's what this is:
   x = (2 * x + (uint32_t)div64_64(a, (uint64_t)x*(uint64_t)x)) / 3;

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