On Wed, Dec 18, 2002 at 12:42:58PM -0600, Peter Seebach wrote:
> I started building a kernel without DEBUG, and
> sure enough, Mozilla became unusable.

There is certainly *something* wrong with your setup.  I can quite
happily have multiple concurrent builds, browsers, X, interactive ssh, yadda
yadda all running and not notice interactive degradation.

For the purposes of convincing myself that I don't have the problem,
while I write this email (over ssh to a remote host) I have:

 3 concurrent compiles: my kernel, build.sh, xsrc (with cc -pipe)
 Mozilla reading web pages and another email spool via imap.
 CVS updating pkgsrc
 ssh to a few other hosts, where i occasionally hit keys to make stuff happen.
 rdesktop over ssh to a windows machine.

All of these applications are responsive, and in fact I can honestly
say it's hard for me to notice that the system is any less responsive
than if it was idle.  New web pages come up quickly, I can move
mails between folders on imap, interactive ssh keyboard and rdesktop
response is fine, etc.  I don't have any mp3's handy to try, but I struggle 
to beleive there will be a problem with those, given how "normal"
the system feels otherwise.

I left mozilla alone for a few minutes, then switched to it's
virtual desktop and hit it with opening a dozen new tabs for
newscientist story pages at once.  I swear it didn't even blink.

As noted before, all the disk traffic is going through cgd, which
seems like it should exacerbate load problems, but just doesn't.
Certainly, having 512M of RAM helps, not least because the disk is
actually just ticking gently and not busy at all:

> iostat 5 5
      tty            wd0             cd0            cgd0             cpu
 tin tout  KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s  us ni sy in id
   3  649  7.26  38 0.27   0.00   0 0.00   7.26  38 0.27  18  0  7  1 75
   0 1360 15.63  24 0.36   0.00   0 0.00  15.63  24 0.36  77  0 22  1  0
   0  807  4.20 180 0.74   0.00   0 0.00   4.20 180 0.74  77  0 22  1  0
   0  729 16.84  15 0.25   0.00   0 0.00  16.84  15 0.25  85  0 15  0  0
   0 1188 19.77  14 0.27   0.00   0 0.00  19.77  14 0.27  81  0 19  0  0


top says:
load averages:  7.65,  6.85,  4.44                                     09:57:10
89 processes:  4 runnable, 84 sleeping, 1 on processor
CPU states: 61.2% user,  0.0% nice, 38.3% system,  0.5% interrupt,  0.0% idle
Memory: 368M Act, 1308K Inact, 3124K Wired, 41M Exec, 243M File, 54M Free
Swap: 256M Total, 256M Free

So, I don't know what I'm doing right, and you're doing wrong, but
something has seriously unbalanced your system compared to mine.

It's a dell latitude c600, 700Mhz pIII, 512Mb PC-100 RAM, disk on ata-33

Other than what I've already described, and that I build my system
with "COPTS+= -march=pentiumpro", I have done nothing by way of
tuning knobs. Perhaps ppro helps but I doubt *that* much.

> So I reniced Mozilla and X to -20, and it became usable again.  I am now
> leaning towards scheduling.

sure, but scheduling of *what*?

> Hmm.  I have HZ defined to 1000; I wonder if that's a component of this, it
> might mean that I'm losing time to context switches when the system is loaded.

Please try removing it.

--
Dan.