linux-kernel - Re: [PATCH 1/4] ACPI: Add acpi_pr

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Message-ID: <1343146093.3010.336.camel@misato.fc.hp.com>
Date:	Tue, 24 Jul 2012 10:08:13 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	shuah.khan@...com
Cc:	lenb@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
	isimatu.yasuaki@...fujitsu.com, liuj97@...il.com,
	srivatsa.bhat@...ux.vnet.ibm.com, prarit@...hat.com,
	imammedo@...hat.com, vijaymohan.pandarathil@...com,
	shuahkhan@...il.com
Subject: Re: [PATCH 1/4] ACPI: Add acpi_pr_<level>() interfaces

On Tue, 2012-07-24 at 09:55 -0600, Toshi Kani wrote:
> On Thu, 2012-07-19 at 17:43 -0600, Toshi Kani wrote:
> > On Thu, 2012-07-19 at 16:32 -0600, Shuah Khan wrote:
> > > On Thu, 2012-07-19 at 14:51 -0600, Toshi Kani wrote:
> > > 
> > > > If your concern is actually a performance bottleneck in acpi_get_name()
> > > > you found in the code, you should report it to the ACPI CA team.
> > > 
> > > I have tried my best to get you to understand the problems in bigger
> > > picture your patch set can exacerbate. Looking to somebody else to fix
> > > the problems doesn't help. It doesn't look like we can come to an
> > > agreement here, we just have to agree to disagree.
> > 
> > I am not asking someone to fix it.  I tried my best to explain that
> > acpi_get_name() does not lead any performance issue when it is called in
> > the error paths of ACPI drivers, and why we have to call it to obtain an
> > object path info for error analysis.  If you still believe there is a
> > performance issue in calling acpi_get_name() under this context, please
> > help us understand where the performance bottleneck is in the code.  (I
> > hope you just concerned it because it has "acpi_" prefix...) I will then
> > work on the issue with the ACPI CA team.
> 
> I have measured acpi_pr_<level>() to make sure my statement is correct.
> Here are the results:
> 
> Avg. acpi_get_name()		 587 ns
> Avg. printk()			3420 ns
> Avg. kfree()			 238 ns
> Avg. acpi_get_time()+kfree()	 825 ns
> 
> The results indicate that acpi_pr_<level>() has 20% increase of the time

Oops, I should have stated that it is 24% increase to printk(), or 20%
of time in acpi_pr_<level>().

-Toshi


> compared to the regular printk(), which is less than 1 us.  I believe
> the results endorse my statement, and may not cause any performance
> issue to the error paths of the ACPI drivers.
> 
> -Toshi
> 
> 
> > Thanks,
> > -Toshi
> > 
> > 
> > 
> > > caio,
> > > -- Shuah
> > > 
> > 
> 


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