linux-kernel - Re: [PATCH 1/4] cputime: Generalize CONFIG_VIRT_CPU

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Message-ID: <20120816143851.GI19716@somewhere>
Date:	Thu, 16 Aug 2012 16:38:53 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Paul Mackerras <paulus@...ba.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 1/4] cputime: Generalize CONFIG_VIRT_CPU_ACCOUNTING

On Thu, Aug 16, 2012 at 04:00:44PM +0200, Martin Schwidefsky wrote:
> On Thu, 16 Aug 2012 14:55:59 +0200
> Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
> > On Thu, Aug 16, 2012 at 07:38:17PM +1000, Benjamin Herrenschmidt wrote:
> > > On Thu, 2012-08-16 at 09:53 +0200, Martin Schwidefsky wrote:
> > > > Hmm, ok. But then the description should be reworded not to be specific to
> > > > the power architecture (the part of the message about "This also enables
> > > > accounting of stolen time on logically-partitioned systems running on IBM
> > > > POWER5-based machines."). 
> > > 
> > > Which is not very helpful to somebody running on a POWER6 or 7 (which
> > > also support that option just fine :-)
> > > 
> > > So yes, the description should definitely be improved.
> > 
> > All right. How about something like the below?
> > 
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 894b073..5f5f8c2 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -276,9 +276,9 @@ config VIRT_CPU_ACCOUNTING
> >  	  accounting.  This is done by reading a CPU counter on each
> >  	  kernel entry and exit and on transitions within the kernel
> >  	  between system, softirq and hardirq state, so there is a
> > -	  small performance impact.  This also enables accounting of
> > -	  stolen time on logically-partitioned systems running on
> > -	  IBM POWER5-based machines.
> > +	  small performance impact.  In the case of IBM POWER > 5, this
> > +	  also enables accounting of stolen time on logically-partitioned
> > +	  systems.
> > 
> >  config BSD_PROCESS_ACCT
> >  	bool "BSD Process Accounting"
> > 
> 
> VIRT_CPU_ACCOUNTING will enable steal time for s390 as well.

Ah right. Fixed below:

diff --git a/init/Kconfig b/init/Kconfig
index 894b073..c40d0fb 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -276,9 +276,9 @@ config VIRT_CPU_ACCOUNTING
 	  accounting.  This is done by reading a CPU counter on each
 	  kernel entry and exit and on transitions within the kernel
 	  between system, softirq and hardirq state, so there is a
-	  small performance impact.  This also enables accounting of
-	  stolen time on logically-partitioned systems running on
-	  IBM POWER5-based machines.
+	  small performance impact.  In the case of s390 or IBM POWER > 5,
+	  this also enables accounting of stolen time on logically-partitioned
+	  systems.
 
 config BSD_PROCESS_ACCT
 	bool "BSD Process Accounting"
--
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