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

From: Alexander Viro (viro@math.psu.edu)
Date: Mon Jan 28 2002 - 19:30:37 EST


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.

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