Re: High load average on disk I/O on 2.6.17-rc3

[Avi Kivity <avi@argo.co.il>]

Russell King wrote:
> Why do you think that?  exim uses the load average to work out whether
> it's a good idea to spawn more copies of itself, and increase the load
> on the machine.
>
> Unfortunately though, under 2.6 kernels, the load average seems to be
> a meaningless indication of how busy the system is from that point of
> view.
>
> Having a single CPU machine with a load average of 150 and still feel
> very interactive at the shell is extremely counter-intuitive.
>   

It's even worse: load average used to mean the number of runnable 
processes + number of processes waiting on disk or NFS I/O to complete, 
a fairly bogus measure as you have noted, but with the aio interfaces 
one can issue enormous amounts of I/O without it being counted in the 
load average.

To make such decisions real, one needs separate counters for cpu load 
and for disk load on the devices one is actually using.

-- 
error compiling committee.c: too many arguments to function