Messages in this thread | | | Date | Wed, 18 Jan 2017 10:01:37 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH 1/8] Documentation, x86: Documentation for Intel Mem b/w allocation user interface |
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On Tue, 17 Jan 2017, Shivappa Vikas wrote: > On Mon, 16 Jan 2017, Thomas Gleixner wrote: > > This interface is really crap. The natural way to express it is: > > > > Requested Bandwidth = X % > > I wanted to do it this way which did seem more intuitive but the issue is with > the non-linear scale which the hardware does not guarantee a particular > percentage for a particular value. Or we don't know the curve for delay value > vs. actual b/w throttled. > > ex: in non linear scale , the granularity is 2^n. > Max : 512 > > Say a value of 256 is not guaranteed to have 50% or even follow a curve where > we can calculate the corresponding percentage.
The question is whether this non linear scale thing is just a first implementation attempt and any sane hardware in the future will use the percentage value (which is an approximation as well).
If that non-linear scale is not going to be prevalent, then we really can live with the fallout of a particular CPU type.
If it's going to stay, then Intel should be able to provide simple tables which give us the required information for a particular CPU model.
Thanks,
tglx
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