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    SubjectRe: [00/41] Large Blocksize Support V7 (adds memmap support)
    On Sun, 16 September 2007 00:30:32 +0200, Andrea Arcangeli wrote:
    >
    > Movable? I rather assume all slab allocations aren't movable. Then
    > slab defrag can try to tackle on users like dcache and inodes. Keep in
    > mind that with the exception of updatedb, those inodes/dentries will
    > be pinned and you won't move them, which is why I prefer to consider
    > them not movable too... since there's no guarantee they are.

    I have been toying with the idea of having seperate caches for pinned
    and movable dentries. Downside of such a patch would be the number of
    memcpy() operations when moving dentries from one cache to the other.
    Upside is that a fair amount of slab cache can be made movable.
    memcpy() is still faster than reading an object from disk.

    Most likely the current reaction to such a patch would be to shoot it
    down due to overhead, so I didn't pursue it. All I have is an old patch
    to seperate never-cached from possibly-cached dentries. It will
    increase the odds of freeing a slab, but provide no guarantee.

    But the point here is: dentries/inodes can be made movable if there are
    clear advantages to it. Maybe they should?

    Jörn

    --
    Joern's library part 2:
    http://www.art.net/~hopkins/Don/unix-haters/tirix/embarrassing-memo.html
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