If you have plenty of memory and are using 1.5, you may try to bump 
BUFCACHE or BUGPAGES (see options(4)) or/and use MFS on /tmp.

NetBSD -current has integrated UBC, so it uses all available machine
memory as I/O buffers automatically. Thus, the reponsiveness
should be (much) better on -current for your scenario (plenty of RAM,
slow disk).

Jaromir

Dwight Tuinstra wrote:
> Tyrel Beede wrote:
> > 
> > I recently replaced my 4.5 GB UW SCSI @ 7200 rpm drive with an IDE 30 GB
> > @ 5400 rpm.  The switch wasn't optional and I've come to notice that the
> > new drive lags with interactive preformance every now and then.  For
> > example I'll be running a vi session and things will just kinda bog
> > down, it seems to occur at random points( some of the time just after a
> > reboot and others after the machine has been up for a few days ).  The
> > lag is kinda like working with a vi session over a slow telnet link.
> > I'll type on the keyboard and a few seconds later the commands will show
> > up.  I've got 96 megs of ram in the machine and I don't even have X
> > installed so the machine isn't really being hit hard for memory.  This
> > problem isn't really that big because the lag only happens every now and
> > then... maybe once a day.  But it never happend on my SCSI drive running
> > the same kernel.  Anybody have any tuning ideas?
> 
> I've had a similar problem with response lag lately.  The
> system is a fresh install from snapshot of 1.5.1-BETA.  The
> problem isn't just vi, though.  I sometimes notice it just 
> when doing an `ls':
> 
>   1) login to several virtual ttys (not even in X, just on console)
>   2) start a disk-intensive job running on one or more ttys 
>        (eg, untar pkgsrc on one and rebuild kernel on another)
>        and let it run for a while.
>   3) switch to a free tty and type `ls'.  1-3 second lag.
>   4) typing `ls' again immediately gets a quick response.
> 
> The disk is an older 5400 rpm IDE model, PIO 4.  There's also
> another, even older 5400 rpm drive on the IDE cable, but it's
> not even mounted (but I think I saw the behavior even when it
> was completely disconnected).  Unfortunately, it'll be at least
> a week or two before the HDs are upgraded.
> 
> >From the behavior, I'd guess its something to do with buffer/
> cache behavior not being tuned.  The system I'm seeing this on
> has plenty of memory (256Mb) and speed (1Ghz Athlon T-bird on
> an IWill KK266 mobo (latest VIA Athlon chipset) ).
> 
> If more details are wanted, I can supply them (the machine's at
> home, modem not yet working right either, so this is written
> from memory while at work).  Let me know what data you'd like.
> 
>   --Dwight Tuinstra
>     tuinstra@clarkson.edu
> 


-- 
Jaromir Dolecek <jdolecek@NetBSD.org>      http://www.ics.muni.cz/~dolecek/
NetBSD - just plain best OS! -=<>=- Got spare MCA cards or docs? Hand me them!