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Date: Thu, 08 Nov 2001 23:35:04 -0800
From: Andrew Morton <akpm@zip.com.au>
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Subject: Re: speed difference between using hard-linked and modular drives?
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Ingo Molnar wrote:
> 
> On Thu, 8 Nov 2001, Andrew Morton wrote:
> 
> > Well on my setup, there are more hash buckets than there are pages in
> > the system.  So - basically empty.  If memory serves me, never more
> > than two pages in a bucket.
> 
> how much RAM and how many buckets are there on your system?
> 

urgh.  It was ages ago.  I shouldn't have stuck my head up ;)

I guess it was 256 megs:

Kernel command line: ...  mem=256m
Page-cache hash table entries: 65536 (order: 6, 262144 bytes)

And that's one entry per page, yes?

I ended up concluding that

a) The hash is sucky and
b) Except for certain specialised workloads, a lookup is usually
   associated with a big memory copy, so none of it matters and
c) given b), the page cache hashtable is on the wrong side of the
   size/space tradeoff :)

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