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SubjectRe: [PATCH] x86_32: trim memory by updating e820 v3
On Tue, Apr 29, 2008 at 12:19 PM, Eric W. Biederman
<> wrote:
> "Yinghai Lu" <> writes:
> >> The potential problem isn't while we reprogram the MTRRs, the potential
> >> problem is mapping the SMM area uncachable. In which case we will
> >> make each SMM interrupt drastically slower. Which can have all kinds of
> >> unpleasant side effects.
> >
> > and ACPI area too.
> True but at least that one is visible.
> > that only try to make the continuous to discrete layout. and still try
> > to cover all that is (WBs - UC) directly with WB.
> > only thing is that could run out of MTRR..., and mtrr_gran_size is
> > used to avoid that.
> > then some RAM that is less than mtrr_gran_size could be dumped.
> > so mtrr_gran_size could do sth.
> > anyway this patch only can meet one end.
> > for example Mika Fischer's system doesn't need to trim any RAM in MTRR.
> > but for Gabriel's system may need to trim some RAM in MTRR.
> Right. Ram trimming (changing memory from WB to UC) is the potential
> problem.
> See my other post, in short I think we can address safely address all
> of the systems where the only problem is the selection of MTRRs by the

BIOS should provide the selection...

> Then have an option (mtrr_chunk_size) for RAM trimming that is
> off by default.

Yes. there is CONFIG option and boot command line to enable it.


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