Re: [reiserfs-dev] Re: Note describing poor dcache utilization under high memory pressure

[Josh MacDonald]

Quoting Alexander Viro ([e-mail]):
> 
> 
> On Tue, 29 Jan 2002, Hans Reiser wrote:
> 
> > This fails to recover an object (e.g. dcache entry) which is used once, 
> > and then spends a year in cache on the same page as an object which is 
> > hot all the time.  This means that the hot set of objects becomes 
> > diffused over an order of magnitude more pages than if garbage 
> > collection squeezes them all together.  That makes for very poor caching.
> 
> Any GC that is going to move active dentries around is out of question.
> It would need a locking of such strength that you would be the first
> to cry bloody murder - about 5 seconds after you look at the scalability
> benchmarks.

We're not talking about actively referenced entries, we're talking about
entries on the d_lru list with zero references.  Relocating those objects
should not require any more locking than currently required to remove and
re-insert the dcache entry.  Right?

-josh

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