Re: funny idle time from time
On Sat, Sep 01, 2001 at 12:12:46PM +1000, Craig Sanders wrote:
> On Sat, Sep 01, 2001 at 11:35:05AM +1000, Brian May wrote:
> > Also, if a computer is running slowly, but top says the CPU has plenty
> > of idle time and free RAM, is there anyway I can find out what is
> > wrong?
>
> most likely slow disks.
Probably. I will have to keep my eyes open if the disks are being
accessed when the system is going slowly.
> > I noticed a Pentium system just before, which seemed too slow to a
> > crawl while doing anacron stuff on startup. However, top reported the
> > mandb command was only using 10% CPU time.
>
> that's not at all unusual.
>
> most processes are I/O bound, not CPU bound. CPUs are so fast these
> days that unless you're doing serious number crunching or 3d rendering,
> the CPU sits idle waiting for data to/from disk & memory.
>
> mandb is definitely an I/O-bound application - most of what it does is
> reading in the man pages to build an index.
True.
> > So while I would expect some slow down, this seemed excessive (X
> > windows took ages to update, etc). Mozilla and X were the only other
> > programs "running" (if you discount the idle system daemons).
> >
> > I have /home NFS mounted, but would assume that this couldn't be a
> > problem...?
>
> nfs isn't noted for being fast.
>
> in fact, it's notorious for being slow (although if it is tuned right
> and you're using fast network cards/switches it can be faster than slow
> local disks).
I have 100Mbps network cards and a Ethernet switch...
> if you have a cron/anacron process which is scanning /home (e.g.
> locate's updatedb or tripwire or sxid) then it's going to take ages.
Does locate look under /home? I have a vague feeling this was ocnfigurable
(or am I thinking of checksecurity?) so I probably should check.
Yuck. I hate locate. I never seem to use it either...
> mozilla saves a lot of stuff to directories underneath $HOME - e.g.
> cached pages/files.
Hmmm... As far as I can tell, you can't even change that. Although I
can never quite work out why I have up to 3 caches (squid, sometimes
wwwoffle, and mozilla) but nothing ever seems to get cached (unless it
is small and insigificant)...
Another offender is probably the gimp, it requires
a swap directory (IIRC).
I have tried telling gimp to use a file like /tmp/.bam-gimp, but Gimp
doesn't seem to understand that it is suppost to create the directory
:-(
Instead, it seems to start OK, but then this message box appears
that Gimp may run unreliably because it couldn't find the swap
space. Arrgghh!
I am a bit nervous about setting it to just /tmp (won't that conflict
with other users?)
So one day I probably should file a bug report against gimp: should create
swap directory if it doesn't exist on startup. Assuming such a bug
report doesn't already exist.
--
Brian May <bam@debian.org>
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