On Sun, Jan 21, 2001 at 02:48:29PM +0100, Wojciech Puchar wrote:
> > [...]
> > Don't know, I didn't look closely at the linux driver :)
> i think it's due to raw device - in linux you can't read without buffering
> and lot of memcpy operation.

Yes, that's possible.

> > > quite responsible even of heavy disk load including writes.
> > 
> > The NetBSD VM is better than linux's under load (on the other hand, it's a bit
> > slower when you have plenty of RAM - need to chose :). Also, linux has
> > a dynamically sized buffer cache which allows to flush pages to RAM to
> > use them as buffer cache when there's a lot of filesystem activity.
> > So under linux pages of the program you're using can be flushed to swap to
> > be remplaced by buffer caches.
> i know it - especially after copying for eg. whole CD-ROM to disk i have a
> lot of swapped programs while having plenty of RAM. 

Yes. All system I know using dynamic buffer caches have more or less this 
problem.

> [...]
> it was tested with softdep enabled!
> i think it's a problem netbsd do maximum of something like 64-128kB writes
> not more. can it be changed?

64K, yes. I don't think linux does more. But linux, with a completely
async filesystem, may be able to cluster more metadata writes.

>
> and can be /usr/var?
> 
> /var (at least in linux) can be VERY large because of /var/spool/mail,
> mqueue

Same here. Then make 3 partitions instead of 2 (/, /var, /usr :)
If it's for a mail server I'd strongly recommends to have a separate /var
(on dedicated mail server I even have /var, /var/mail and /var/spool/mqueue
partitions :)

--
Manuel Bouyer <bouyer@antioche.eu.org>
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