Right, it's swapping out the controlling structures without swapping
out the pages themselves that's harder.
>> IMHO, it's better not to fill memory with crap in the first place than
>> to invent complex methods of managing and shrinking it afterwards. You
>> only get into pathalogical conditions under sharing situation, else
>> it's limited to about 1% of RAM (bad, but manageable) ... thus providing
>> this sort of sharing nixes the worst of it. Better cache warmth on
>> switches (for TLB misses), faster fork+exec, etc. are nice side-effects.
>
> I will agree with that if everything works so the sharing happens,
> this is a nice feature.
I think it will for most of the situations we run aground with now
(normally 5000 oracle tasks sharing a 2Gb shared segment, or some
such monster).
>> The ultimate solution is per-object reverse mappings, rather than per
>> page, but that's a 2.7 thingy now.
> ???
>
> Last I checked we already had those in 2.4.x, and still in 2.5.x. The
> list of place the address space is mapped.
It's more complicated than that ... I'll let Rik or one of the K42
guys who understand it better than I do explain it (yeah, I'm wimping
out on you ;-))
M.
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