then it will break on archs with more ram than 1<<(32+PAGE_CACHE_SHIFT).
Also there must be some significant memory overhead that can be
triggered with a certain layout of pages, in some configuration it
should take much more ram than the hashtable if I understood well how it
works.
Also its O(1) may be slower than the O(N) of the hashtable in the 99% of
the cases.
>
> We could, in fact, make all page caches use a fixed-depth tree, which is
> clearly O(1). But the radix tree is slightly faster and tends to use less
> memory under common loads, so..
>
> Remember: you must NOT ignore the constant part of a "O(x)" equation.
> Hashes tend to be effectively O(1) under most loads, but they have cache
> costs, and they have scalability costs that a radix tree doesn't have.
the scalability cost I obviously agree :) (however on some workload with
all tasks on the same inode, the scalability cost remains the same).
Andrea
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