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SubjectRe: Benchmarking 2.2 and 2.4 using hdparm and dbench 1.1
[regarding the buffer cache hash size and bad performance on machines
with little memory... (<32MB)]

On Tue, 9 Jan 2001, Anton Blanchard wrote:
> > Where is the size defined, and is it easy to modify?
>
> Look in fs/buffer.c:buffer_init()

I experimented some, and increasing the huffer cache hash to the 2.2
levels helped a lot, especially for 16 MB memory. The difference is huge,
64 kB in 2.2 vs 1 kB in 2.4 for a 32 MB memory machine.

> I havent done any testing on slow hardware and the high end stuff is
> definitely performing better in 2.4, but I agree we shouldn't forget
> about the slower stuff.

Being able to tune the machine for both high and low end systems is
neccessary, and if Linux can tune itself, that's of course the best.

> Narrowing down where the problem is would help. My guess is it is a TCP
> problem, can you check if it is performing worse in your case? (eg ftp
> something against 2.2 and 2.4)

Nope, TCP performance seems more or less unchanged. I will keep
investigating, and get back when I have more info.

/Tobias


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