Re: mmotm 2009-04-10-02-21 uploaded - forkbombed by work_for_cpu

[Ali Gholami Rudi]

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@xxxxxxxxxxxxxxxxxxxx>
  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@xxxxxxxxxxxxxxxxxxxx>
        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@xxxxxx
      Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
      Cc: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
      Cc: Len Brown <len.brown@xxxxxxxxx>
      Cc: Zhao Yakui <yakui.zhao@xxxxxxxxx>
      Acked-by: Dave Jones <davej@xxxxxxxxxx>
      Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
      Tested-by: Mike Galbraith <efault@xxxxxx>
      Cc: "Zhang, Yanmin" <yanmin_zhang@xxxxxxxxxxxxxxx>
      Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
      Acked-by: Ingo Molnar <mingo@xxxxxxx>
      [ 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@xxxxxxxxxxxxxxxxxxxx>

Should I include more info?

Regards,
Ali
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