Re: [PATCH] CKRM [2/8] More accurate account for CPU & IO scheduling

[Andi Kleen <ak@muc.de>]

Gerrit Huizenga <gh@us.ibm.com> writes:

> --- linux-2.6.11-rc5.orig/kernel/sched.c	2005-02-23 20:03:10.000000000 -0800
> +++ linux-2.6.11-rc5/kernel/sched.c	2005-02-24 00:54:56.572070756 -0800
> @@ -288,6 +288,8 @@
> @@ -2806,6 +2809,8 @@
>  
>  	sched_info_switch(prev, next);
>  	if (likely(prev != next)) {
> +		add_delay_ts(next, waitcpu_total, next->timestamp, now);
> +		inc_delay(next, runs);

This is an extremly hot path. I think it needs far more justification
why you really need this. In general we try to keep the context
switch as fast as possible; I don't think it's a good idea to add 
accounting like this.

How about you investigate ways to do this using samples 
from the regular statistics timers?  If it's good enough for all
other CPU accounting, it should be good enough for this relatively
obscure metric too.
  
-Andi