Re: [PATCH 3/4] UefiCpuPkg/MtrrLib: Update algorithm to calculate optimal settings

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

The old version is not just slow.
It cannot work in certain cases. That's why the new version was developed.

The new version adds a new API which allows caller to pass in the scratch
buffer instead of using the stack. If a platform has limited stack, it can use
that API.

Thanks/Ray

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Jordan Justen
> Sent: Thursday, November 9, 2017 2:56 PM
> To: Ni, Ruiyu <ruiyu.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>
> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; edk2-
> devel@lists.01.org; Yao, Jiewen <jiewen.yao@intel.com>; Dong, Eric
> <eric.dong@intel.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Subject: Re: [edk2] [PATCH 3/4] UefiCpuPkg/MtrrLib: Update algorithm to
> calculate optimal settings
> 
> On 2017-11-08 19:04:35, Ni, Ruiyu wrote:
> > Jordan, Laszlo,
> >
> > I didn't realize that a platform may have less than 4-page stack
> > before memory is ready. If I was aware of that, I would change the
> > default scratch buffer size to 2 page, which should be enough too.
> 
> This does not sound much better. I'm saying that the BASE library should only
> use at most a few hundred bytes of stack.
> 
> Apparently the old algorithm did not use much memory, but perhaps was
> slow? Can we put it back in place for the BASE version of the library?
> Then, we can add a DXE specific version that uses a large buffer which it can
> allocate, and potentially free.
> 
> -Jordan
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