Re: vm/fs meetup details

[Martin Bligh <mbligh@mbligh.org>]

Jörn Engel wrote:
> On Mon, 9 July 2007 09:29:38 +1000, David Chinner wrote:
>> On Sat, Jul 07, 2007 at 12:45:35PM +0200, Jörn Engel wrote:
>>> Oh certainly!  I should dust off my dcache_static patch.  Some dentries
>>> are hands-off for the shrinker, basically mountpoints and tmpfs.  The
>>> patch moves those to a seperate slab cache.
>> I doubt there's enough of those to make any difference - putting all
>> the directories into another slab did little to reduce fragmentation
>> (~18 months ago we tried that), so I don't think that this would help
>> at all...
> 
> Interesting.  I suspect that the de-facto random cache eviction has a
> bigger effect and overshadows everything else.  So the decisive step
> would be to nuke all dentries in a given slab.
> 
> It wouldn't surprise me if your patch did make a difference afterwards.
> With 32 dentries per slab, it doesn't take many pinned objects to pin
> most slabs.

What happened to the patches floating around to stick the dentries for
directories into a different cache? IIRC, they were somewhat problematic
because you don't know what the dentry is used for at allocate time,
but did that ever get fixed / worked around?

M.
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