linux-kernel - Re: [patch] sched: yield debugging

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Message-Id: <1186001617.19777.64.camel@localhost.localdomain>
Date:	Wed, 01 Aug 2007 13:53:37 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [patch] sched: yield debugging

On Tue, 2007-07-31 at 22:33 +0200, Ingo Molnar wrote:

> ok, good! Could you try the updated debug patch below? I've done two 
> changes: made '1' the default, and added the 
> /proc/sys/kernel/sched_yield_granularity_ns tunable. (available if 
> CONFIG_SCHED_DEBUG=y)
> 
> Could you try to change the yield-granularity tunable and see which 
> value gives the best performance? A value of '100000' should in theory 
> give the current (80% degraded) volanomark performance, the default 
> value should give the above '20% down' result. The question is, is '20% 
> down' the best we can get out of it? Does larger/smaller 
> yield-granularity help perhaps? You can change it to any value between 
> 100 usecs and 1 second.
> 

Turning up the granuality helped.  Here's the data I got
for Volanomark performance relative to 2.6.22
Granuality
1000000000  (max)	9% down
 800000000 		8% down
  80000000		13% down
   8000000  		20% down
    100000		56% down

Tim
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