Re: [00/41] Large Blocksize Support V7 (adds memmap support)

["Jörn Engel" <joern@logfs.org>]

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