Top not showing cpu usage even remotely accurately

[Ian Smith]

On Thu, 10 Aug 2006, Chuck Swiger wrote:
 > Ian Smith wrote:
 > > But since running 5.x (5.5-STABLE since 1st Aug) top can show 0.0% idle
 > > but the cpu usages shown don't add up to much of a fraction of 100%.
 > [ ... ]
 > > Any ideas why top hasn't much of a clue about what's consuming cpu? 
 > 
 > Sure, if you're running a parallel make, that will be starting up lots of 
 > short-lived compiler processes which exit quickly; top can only display the 
 > CPU load for those processes which are still running at the time it samples 
 > the system.

Spot on, thanks Chuck.  lastcomm showed a couple of thousand processes
run per minute during several hours of 'make index'; /var/account/acct
was nearly 10MB for that time.  Only one gcc but lots of sh, perl, grep,
awk, sed and such each running < 1 second, being a texty sort of job. 

Cheers, Ian