> i'd do something like this to satisfy higher-order goals:
>
> if (makes_situation_better(this_candidate_page,order))
> swap_out(this_candidate_page);
makes_situation_better() can be improved further, by possibly adding:
1) an 'unswappables bitmaps', basically shadowing the buddy bitmaps, but
showing all the 'impossible to swap out now' pages. Cons: higher
allocation overhead, higher cache/memory usage. Pros: makes the effect of
unswappable pages exactly predictable.
2) 'goals bitmaps', shadowing the buddy bitmaps again, but showing all the
swapouts currently being done to reach one given higher-order goal. Cons:
higher cache/memory usage. Pros: eliminates the exponential nature of
'satisfy higher-order request' allocations, focuses swapouts, reduces the
number of 'accidentally destroyed lower-order but useful' pages.
i think both of these are still much better than reverse page tables.
-- mingo
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