From owner-freebsd-performance@FreeBSD.ORG  Sun Aug  7 21:43:38 2005
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Date: Sun, 7 Aug 2005 21:43:38 +0000
From: Darren Reed <darrenr@hub.freebsd.org>
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Subject: Re: [RFC] Bumping ufs.dirhash_maxmem to a larger value?
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On Mon, Aug 08, 2005 at 02:51:29AM +0800, Xin LI wrote:
...
> My proposal is to increase the default dirhash_maxmem value to at least
> 32MB or 64MB.  Any objections?
> 
> Cons for this, discussed in -developer:
>  - dirhash does not implements automatical mechanism to reduce memory
>    usage in response to system memory pressure, and benefits mainly to
>    large directories, e.g. Maildirs.

So why not make the determination of "dirhash_maxmem" the result of some
calculation(s) that takes into account RAM size, etc ?

The obvious lesson here is that picking a number to be a limit based on
the current size of machines fails the test of time.

Darren