Re: [PATCH 0/4] V4 ia64 SPARSEMEM

Yasunori Goto
2005-09-27T04:53:54Z

Hi David-san.

> > >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.

SPARSEMEM is essential implementation for "memory hotplug" feature now.
It gives basis that system can manage to disable/enable a part of
memory. And it is not only for ia64 but also for ppc64 and x86_64.

Bye.
--
Yasunori Goto