Performance problem since updating from 6.0-RELEASE to 6.0-STABLE last friday

Nate Lawson nate at
Tue Nov 22 12:07:13 PST 2005

Hajimu UMEMOTO wrote:
> Hi,
>>>>>>On Thu, 17 Nov 2005 11:24:16 -0500
>>>>>>Pierre-Luc Drouin <pldrouin at> said:
>>Ok, there is new development. I realized by playing with 
>>debug.acpi.disabled="smbat", debug.acpi.disabled="smbat cmbat" and 
>>debug.acpi.disabled="cmbat", that my laptop battery is not a smbat, 
>>but a cmbat. When I played with hw.acpi.battery.info_expire after to 
>>have applied the patch for acpi_smbat.c, it was freezing less often 
>>because that sysctl variable was shared by both cmbat and smbat. So I 
>>can only get battery status from cmbat (disabling cmbat disables the 
>>use of acpiconf -i loop). To get the status of my battery via cmbat 
>>was working fine up to 6.0-RELEASE (included), but makes my laptop to 
>>freeze since I upgraded to 6.0-stable with Nov 10th sources. What 
>>change related to cmbat between 6.0-release and 6.0-stable could be 
>>causing this?
> pldrouin> Has someone found how to fix this problem in -stable?
> Perhaps, I found the cause.  acpi_cmbat_get_bif() is heavy process,
> and it was called only when ACPIIO_CMBAT_GET_BIF ioctl was issued
> explicitly, until smbat stuff was committed.  However,
> acpiio_cmbat_get_bif() is called from every
> acpi_battery_get_battinfo() call, now.
> The attached patch will bring back to former behavior.  Please try it
> and let me know the result.
> It is against 7-CURRENT as of today.  If you want to try it on
> 6-STABLE, you need to apply following diff before applying it:

Thank you for tracking this down.  It is interesting that BIF is 
heavyweight while BST is not.  I guess that is expected behavior by OEMs 
which only test on Windows and so not everyone makes BIF simple.  On my 
laptops, BIF is as fast as BST.

I don't like the patch approach (changing the API), however.  Let me 
look at it and commit a fix that doesn't change the API.


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