Re: funny idle time from time
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.
> 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.
> 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).
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.
mozilla saves a lot of stuff to directories underneath $HOME - e.g.
cached pages/files.
craig
--
craig sanders <cas@taz.net.au>
Fabricati Diem, PVNC.
-- motto of the Ankh-Morpork City Watch
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