linux-kernel - Re: mmotm 2009-04-10-02-21 uploaded

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Date:	Wed, 15 Apr 2009 12:45:34 +0430
From:	Ali Gholami Rudi <ali@...i.ir>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Valdis.Kletnieks@...edu, Mike Travis <travis@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	mm-commits@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>,
	Dave Jones <davej@...hat.com>, Len Brown <lenb@...nel.org>
Subject: Re: mmotm 2009-04-10-02-21 uploaded - forkbombed by work_for_cpu

Hi,

In today's tip (v2.6.30-rc2), when my cpu is idle (and the ondemand
governor correctly uses the lowest frequency) the temperature of my CPU
rises to above 50^C till the fan turns on (it used to be about 40^C
before).  Git bisect points to this patch:

  commit 01599fca6758d2cd133e78f87426fc851c9ea725
  Author: Andrew Morton <akpm@...ux-foundation.org>
  Date:   Mon Apr 13 10:27:49 2009 -0700
  
      cpufreq: use smp_call_function_[single|many]() in acpi-cpufreq.c
      
      Atttempting to rid us of the problematic work_on_cpu().  Just use
      smp_call_fuction_single() here.
      
      This repairs a 10% sysbench(oltp)+mysql regression which Mike reported,
      due to
      
        commit 6b44003e5ca66a3fffeb5bc90f40ada2c4340896
        Author: Andrew Morton <akpm@...ux-foundation.org>
        Date:   Thu Apr 9 09:50:37 2009 -0600
      
            work_on_cpu(): rewrite it to create a kernel thread on demand
      
      It seems that the kernel calls these acpi-cpufreq functions at a quite
      high frequency.
      
      Valdis Kletnieks also reports that this causes 70-90 forks per second on
      his hardware.
      
      Cc: Valdis.Kletnieks@...edu
      Cc: Rusty Russell <rusty@...tcorp.com.au>
      Cc: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
      Cc: Len Brown <len.brown@...el.com>
      Cc: Zhao Yakui <yakui.zhao@...el.com>
      Acked-by: Dave Jones <davej@...hat.com>
      Cc: Thomas Gleixner <tglx@...utronix.de>
      Tested-by: Mike Galbraith <efault@....de>
      Cc: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
      Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
      Acked-by: Ingo Molnar <mingo@...e.hu>
      [ Made it use smp_call_function_many() instead of looping over cpu's
        with smp_call_function_single()    - Linus ]
      Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

Should I include more info?

Regards,
Ali
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