Re: speed difference between using hard-linked and modular drives?

Andrew Morton
2001-11-09T07:40:52Z

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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