Re: Proposed module: tracker

[Joe Shaw <joeshaw novell com>]

Hi,

Jamie McCracken wrote:
> point 2 is scheduled at nice +19 (same with Ionice +7) so it only uses 
> more cpu if its idle. 

That's not quite how the nice level works, at least in Linux.  Higher 
nice values get a shorter timeslice, so they merely have less time to 
get their work in before other tasks are scheduled.  So all processes 
fight for the CPU, it's just that (in this case) Tracker gets it less often.

Also note that the scheduler actually adjusts nice values under the 
covers based on how much CPU is being used.  Processes with higher CPU 
utilization actually have their nice value *lowered*, with the idea that 
the CPU utilization is a short-lived thing.  So it might be lowered to 
nice level +14.

The same thing goes for ionice if it's in the "best effort" IO class. 
Only in the "idle" class does IO happen when no other IO happens, but to 
set that you need to be root due to potential DoS attacks with priority 
inversion.

Joe