1G x86 machines are becoming fairly common and they either need to waste
ram or turn on himem.
David Lang
On Mon, 4 Mar 2002, Martin J. Bligh wrote:
> > They're not in my tree and for very good reasons, Ben did such mistake
> > the first time at some point during 2.3. You've a big downside with the
> > per-zone information, all normal machines (like with 64M of ram or 2G of
> > ram) where theorical O(N) complexity is perfectly fine for lowmem
> > dma/normal allocations, will get hurted very much by the per-node lrus.
>
> I'm not sure why it has to be a big impact for the "common desktop"
> machine - they should only have one zone anyway. ZONE_DMA should
> shrivel up and die in a lonely corner. Yeah, OK, keep it as a
> back-compatibility option for those museum pieces that need it,
> but personally I'd make ISA DMA support a config option defaulting
> to off ... maybe it's possible to do dynamically (just stick no
> pages in it, though I suspect it's too late by the time we know).
> Hardly any common desktop will need HIGHMEM support, and those
> that do will probably get enough kickback from per-zone things to
> pay for the cost.
>
> To me, per-node would probably be about as good, but I don't think
> per-zone is as bad as you think.
>
> > making it a per-lru spinlock is natural scalability optimization,
> > but anyways pagemap_lru_lock isn't a very critical spinlock.
>
> see my other email - it's worse in rmap.
>
> M.
>
>
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