Re: More latency regressions with 2.6.11-rc4-RT-V0.7.39-02

[Nick Piggin]

Lee Revell wrote:
> On Thu, 2005-02-24 at 12:29 +1100, Nick Piggin wrote:
>
> > Lee Revell wrote:
> >
> > > IIRC last time I really tested this a few months ago, the worst case
> > > latency on that machine was about 150us.  Currently its 422us from the
> > > same clear_page_range code path.
> >
> > Well it should be pretty trivial to add a break in there.
> > I don't think it can get into 2.6.11 at this point though,
> > so we'll revisit this for 2.6.12 if the clear_page_range
> > optimisations don't get anywhere.
>
>
> Agreed, it would be much better to optimize this away than just add a
> scheduling point.  It seems like we could do this lazily.

Oh? What do you mean by lazy? IMO it is sort of implemented lazily now.
That is, we are too lazy to refcount page table pages in fastpaths, so
that pushes a lot of work to unmap time. Not necessarily a bad trade-off,
mind you. Just something I'm looking into.

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