linux-kernel - Re: [RFC] sched: The removal of idle

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Date:	Fri, 15 Feb 2013 10:05:41 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Turner <pjt@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Clark Williams <clark@...hat.com>,
	Andrew Theurer <habanero@...ibm.com>
Subject: Re: [RFC] sched: The removal of idle_balance()

On Fri, 2013-02-15 at 16:45 +0900, Joonsoo Kim wrote:
> Hello, Steven.

> - Before Patch
> Permance counter stats for 'perf bench sched messaging -g 300' (10 runs):
> 
>       40847.488740 task-clock                #    3.232 CPUs utilized            ( +-  1.24% )
>            511,070 context-switches          #    0.013 M/sec                    ( +-  7.28% )
>            117,882 cpu-migrations            #    0.003 M/sec                    ( +-  5.14% )
>          1,360,501 page-faults               #    0.033 M/sec                    ( +-  0.12% )
>    118,534,394,180 cycles                    #    2.902 GHz                      ( +-  1.23% ) [50.70%]
>    <not supported> stalled-cycles-frontend 
>    <not supported> stalled-cycles-backend  
>     46,217,340,271 instructions              #    0.39  insns per cycle          ( +-  0.56% ) [76.93%]
>      8,592,447,548 branches                  #  210.354 M/sec                    ( +-  0.75% ) [75.50%]
>        273,367,481 branch-misses             #    3.18% of all branches          ( +-  0.26% ) [75.49%]
> 
>       12.639049245 seconds time elapsed                                          ( +-  2.29% )
> 
> - After Patch
>  Performance counter stats for 'perf bench sched messaging -g 300' (10 runs):
> 
>       42053.008632 task-clock                #    2.932 CPUs utilized            ( +-  0.91% )
>            672,759 context-switches          #    0.016 M/sec                    ( +-  2.76% )
>             83,374 cpu-migrations            #    0.002 M/sec                    ( +-  4.46% )
>          1,362,900 page-faults               #    0.032 M/sec                    ( +-  0.20% )
>    121,457,601,848 cycles                    #    2.888 GHz                      ( +-  0.93% ) [50.75%]
>    <not supported> stalled-cycles-frontend 
>    <not supported> stalled-cycles-backend  
>     47,854,828,552 instructions              #    0.39  insns per cycle          ( +-  0.36% ) [77.09%]
>      8,981,553,714 branches                  #  213.577 M/sec                    ( +-  0.42% ) [75.41%]
>        274,229,438 branch-misses             #    3.05% of all branches          ( +-  0.20% ) [75.44%]
> 
>       14.340330678 seconds time elapsed                                          ( +-  1.79% )
> 

Interesting that perf bench gives me a little better performance with
the idle_balance than without too. But hackbench still shows a huge
performance without idle_balance. The funny part about that is perf
bench sched messaging is based off of hackbench??

I would really like to know why hackbench gets a 50% performance without
idle balancing. Perhaps it is some kind of fluke :-/

-- Steve


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