linux-kernel - Re: 2.6.20-rc6-mm3

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Date:	Fri, 02 Feb 2007 09:39:16 -0800
From:	Daniel Walker <dwalker@...sta.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.20-rc6-mm3

On Mon, 2007-01-29 at 20:45 -0800, Andrew Morton wrote:
> Temporarily at
> 
> 	http://userweb.kernel.org/~akpm/2.6.20-rc6-mm3/
> 
> Will appear later at
> 
> 	ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20-rc6/2.6.20-rc6-mm3/
> 

I was running likely profiling and I noticed that when I turn on the
"tickless" option I get the following line, 

+unlikely | 21111208|  9367278  need_resched()@:include/linux/sched.h@...7

This means that this line is 21111208 true, and 9367278 false.

This existed on bootup, and stayed after about 7 hours of runtime
(mostly idle). Since need_resched is a "static inline" there are
multiple instances of need_resched() in the kernel. If I turn off the
"tickless" feature this wrong unlikely disappears, and the output looks
like this,

 unlikely |        0|      169  need_resched()@:include/linux/sched.h@...7
 unlikely |        0|       94  need_resched()@:include/linux/sched.h@...7
 unlikely |        0|       63  need_resched()@:include/linux/sched.h@...7
 unlikely |        0|       19  need_resched()@:include/linux/sched.h@...7
 unlikely |        0|      379  need_resched()@:include/linux/sched.h@...7
 unlikely |        1|   202596  need_resched()@:include/linux/sched.h@...7
 unlikely |        7|   205929  need_resched()@:include/linux/sched.h@...7
 unlikely |     6461|   271690  need_resched()@:include/linux/sched.h@...7

Only a little after boot. I suppose this could be a natural side effect
of the tickless feature but I thought I would report it anyway.

Daniel

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