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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1343145334.3010.334.camel@misato.fc.hp.com>
Date:	Tue, 24 Jul 2012 09:55:34 -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 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
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
> > 
> 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/