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From: Roy Sigurd Karlsbakk <roy@karlsbakk.net>
Organization: ProntoTV AS
To: "Martin J. Bligh" <Martin.Bligh@us.ibm.com>,
       Andrew Morton <akpm@zip.com.au>
Subject: Re: [BUG+FIX] 2.4 buggercache sucks
Date: Fri, 30 Aug 2002 11:21:06 +0200
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> > I mean - this code solved _my_ problem. Without it the server OOMs within
> > minutes of high load, as explained earlier. I'd rather like a clean fix
> > in 2.4 than this, although it works.
>
> I'm sure Andrew could explain this better than I - he wrote the
> code, I just whined about the problem. Basically he frees the
> buffer_head immediately after he's used it, which could at least
> in theory degrade performance a little if it could have been reused.
> Now, nobody's ever really benchmarked that, so a more conservative
> approach is likely to be taken, unless someone can prove it doesn't
> degrade performance much for people who don't need the fix. One
> of the cases people were running scared of was something doing
> continual overwrites of a file, I think something like:
>
> for (i=0;i<BIGNUMBER;i++) {
> 	lseek (0);
> 	write 4K of data;
> }
>
> Or something.
>
> Was your workload doing lots of reads, or lots of writes? Or both?

I was downloading large files @ ~ 4Mbps from 20-50 clients - filesize ~3GB
the box has 1GB memory minus (no highmem) - so - 900 megs. After some time it 
starts swapping and it OOMs. Same happens with several userspace httpd's

roy

-- 
Roy Sigurd Karlsbakk, Datavaktmester
ProntoTV AS - http://www.pronto.tv/
Tel: +47 9801 3356

Computers are like air conditioners.
They stop working when you open Windows.

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