Re: [PATCH] sched: Fix adverse effects of NFS client on interactive response

[Mike Galbraith <efault@gmx.de>]

At 08:51 AM 1/5/2006 +1100, Peter Williams wrote:

>I think that some of the harder to understand parts of the scheduler code 
>are actually attempts to overcome the undesirable effects (such as those 
>I've described) of inappropriately identifying tasks as interactive.  I 
>think that it would have been better to attempt to fix the inappropriate 
>identifications rather than their effects and I think the prudent use of 
>TASK_NONINTERACTIVE is an important tool for achieving this.

IMHO, that's nothing but a cover for the weaknesses induced by using 
exclusively sleep time as an information source for the priority 
calculation.  While this heuristic does work pretty darn well, it's easily 
fooled (intentionally or otherwise).  The challenge is to find the right 
low cost informational component, and to stir it in at O(1).

The fundamental problem with the whole interactivity issue is that the 
kernel has no way to know if there's a human involved or not.  My 100%cpu 
GL screensaver is interactive while I'm mindlessly staring at it.

         -Mike