Re: [Lhms-devel] Re: [PATCH 0/4] V4 ia64 SPARSEMEM

From: Bob Picco <>
Date: 2005-09-28 00:07:37
David Mosberger-Tang wrote:	[Mon Sep 26 2005, 09:20:08PM EDT]
> On 9/26/05, Luck, Tony <> wrote:
> > >Long term should SPARSEMEM become the default and DISCONTIG+VIRTUAL_MEM_MAP
> > >be obsoleted then we could remove the config files.
> >
> > If benchmarks show no difference, then I'll consolidate the
> > configuration options.  I still think that VIRTUAL_MEM_MAP
> > has a great deal of elegance to it ... auto-sizing to just
> > about any degree of sparseness, but I think we need to
> > simplify.
> Benchmarks cannot prove the absence of a performance difference in
> *general*, they can only do that for specific tests and workloads. 
> So, unless SPARSEMEM actually performs *better* on some benchmarks
> (and no worse on others), the proper course seems to be to stick with
> VIRTUAL_MEM_MAP where SPARSEMEM isn't needed.
> I have voice my objection in the past to Bob's suggestion that
> SPARSEMEM should replace VIRTUAL_MEM_MAP and since then I haven't seen
> any convincing argument why that should be the case, so I do not
> understand why Bob keeps bringing that up.
Well I'm not attempting to stir up controversy. It's just that should SPARSEMEM
and VIRTUAL_MEM_MAP perform equally, then there doesn't appear any point
in retaining both. We are a long way from that decision should there ever
be consensus to make it.
>   --david
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Received on Wed Sep 28 00:06:48 2005

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