[PATCH] Disable slow duplicate object tracking in ACPI_DEBUG

[PATCH] Disable slow duplicate object tracking in ACPI_DEBUG

[Andi Kleen]

The current SUSE 10.0 beta has CONFIG_ACPI_DEBUG enabled. That lead
to severe slowdowns on several machines. One issue was the different
default for ec_burst_mode. Another one was that the object tracking
would always walk the full list of all objects, which lead to kacpid
needing up to 25% of the total CPU time.

This patch disables the slow list walking. It could be probably
replaced with a hash or similar too, but I don't think the duplicate
object tracking is too useful anaywys so I just disabled it.

-Andi

From: ak-l3A5Bk7waGM@public.gmane.org
Subject: Disable linear search in ACPI debugging
Suse-bugzilla: 102565

Looking through all the memory objects all the time is just too slow.
Don't do it.


Signed-off-by: Andi Kleen <ak-l3A5Bk7waGM@public.gmane.org>

Index: linux-2.6.13rc5/drivers/acpi/utilities/utalloc.c
===================================================================
--- linux-2.6.13rc5.orig/drivers/acpi/utilities/utalloc.c
+++ linux-2.6.13rc5/drivers/acpi/utilities/utalloc.c
@@ -674,6 +674,9 @@ acpi_ut_find_allocation (
 {
 	struct acpi_debug_mem_block     *element;
 
+	/* too slow to be usable */
+	return NULL;
+
 
 	ACPI_FUNCTION_ENTRY ();
 


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RE: [PATCH] Disable slow duplicate object tracking in ACPI_DEBUG

[Brown, Len]

Maybe it is time to figure out why SLES has ACPI_DEBUG enabled.
If it is certain warnings and error messages, then perhaps
we should enable those but not all the other misc debug
and paranoia checks that come with ACPI_DEBUG?

thanks,
-Len

ps. ec-burst should be disabled by default in 2.6.12
and 2.6.13-rc6.  there is an option to enable it at boot-time
in -mm, and hopefully we'll get it working there (very) soon
so we can experiment again with ec-burst enabled by default. 

>-----Original Message-----
>From: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org 
>[mailto:acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org] On Behalf Of Andi Kleen
>Sent: Wednesday, August 10, 2005 7:33 AM
>To: acpi-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
>Subject: [ACPI] [PATCH] Disable slow duplicate object tracking 
>in ACPI_DEBUG
>
>
>The current SUSE 10.0 beta has CONFIG_ACPI_DEBUG enabled. That lead
>to severe slowdowns on several machines. One issue was the different
>default for ec_burst_mode. Another one was that the object tracking
>would always walk the full list of all objects, which lead to kacpid
>needing up to 25% of the total CPU time.
>
>This patch disables the slow list walking. It could be probably
>replaced with a hash or similar too, but I don't think the duplicate
>object tracking is too useful anaywys so I just disabled it.
>
>-Andi
>
>From: ak-l3A5Bk7waGM@public.gmane.org
>Subject: Disable linear search in ACPI debugging
>Suse-bugzilla: 102565
>
>Looking through all the memory objects all the time is just too slow.
>Don't do it.
>
>
>Signed-off-by: Andi Kleen <ak-l3A5Bk7waGM@public.gmane.org>
>
>Index: linux-2.6.13rc5/drivers/acpi/utilities/utalloc.c
>===================================================================
>--- linux-2.6.13rc5.orig/drivers/acpi/utilities/utalloc.c
>+++ linux-2.6.13rc5/drivers/acpi/utilities/utalloc.c
>@@ -674,6 +674,9 @@ acpi_ut_find_allocation (
> {
> 	struct acpi_debug_mem_block     *element;
> 
>+	/* too slow to be usable */
>+	return NULL;
>+
> 
> 	ACPI_FUNCTION_ENTRY ();
> 
>
>
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>


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Re: [PATCH] Disable slow duplicate object tracking in ACPI_DEBUG

[Andi Kleen]

On Wed, Aug 10, 2005 at 10:14:43PM -0400, Brown, Len wrote:
> Maybe it is time to figure out why SLES has ACPI_DEBUG enabled.
> If it is certain warnings and error messages, then perhaps
> we should enable those but not all the other misc debug
> and paranoia checks that come with ACPI_DEBUG?

SLES doesn't have ACPI_DEBUG enabled. 

ACPI_DEBUG is just sometimes enabled in the betas because it makes
it easier to track down ACPI bugs - mostly because of the
tracing options which can be then used without recompiling the kernel

(which BTW seem to also cause considerable 
overhead. One current case is a system where kacpid takes about 1.7%
of CPU and most of that seems to be just tracing functions) 

ACPI_DEBUG_LITE was intended to be a subset that has only the 
needed stuff enabled, but somehow that didn't take off.

-Andi


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September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices
Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA
Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf