linux-kernel - Re: [PATCH 2/5] Add nsecs_to_cputime64 interface for asm-generic -v2

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Date:	Wed, 22 Dec 2010 16:25:46 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, Paul Turner <pjt@...gle.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Shaun Ruffell <sruffell@...ium.com>
Subject: Re: [PATCH 2/5] Add nsecs_to_cputime64 interface for asm-generic
 -v2

On Wed, 22 Dec 2010 06:23:55 -0800
Venkatesh Pallipadi <venki@...gle.com> wrote:

> On Wed, Dec 22, 2010 at 12:30 AM, Martin Schwidefsky
> <schwidefsky@...ibm.com> wrote:
> > On Tue, 21 Dec 2010 17:09:01 -0800
> > Venkatesh Pallipadi <venki@...gle.com> wrote:
> >
> >> Add nsecs_to_cputime64 interface. This is used in following patches that
> >> updates cpu irq stat based on ns granularity info in IRQ_TIME_ACCOUNTING.
> >>
> >> Tested-by: Shaun Ruffell <sruffell@...ium.com>
> >> Signed-off-by: Venkatesh Pallipadi <venki@...gle.com>
> >> ---
> >>  include/asm-generic/cputime.h |    3 +++
> >>  include/linux/jiffies.h       |    1 +
> >>  kernel/time.c                 |   23 +++++++++++++++++++++--
> >>  3 files changed, 25 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/include/asm-generic/cputime.h b/include/asm-generic/cputime.h
> >> index 2bcc5c7..61e03dd 100644
> >> --- a/include/asm-generic/cputime.h
> >> +++ b/include/asm-generic/cputime.h
> >> @@ -30,6 +30,9 @@ typedef u64 cputime64_t;
> >>  #define cputime64_to_jiffies64(__ct) (__ct)
> >>  #define jiffies64_to_cputime64(__jif)        (__jif)
> >>  #define cputime_to_cputime64(__ct)   ((u64) __ct)
> >> +#define cputime64_gt(__a, __b)               ((__a) >  (__b))
> >> +
> >> +#define nsecs_to_cputime64(__ct)     nsecs_to_jiffies64(__ct)
> >>
> >>
> >>  /*
> >
> > If you define a new cputime primitive it is not enough to add it to the
> > generic cputime header. You have to add it to the arch-specific cputime
> > header for ia64, powerpc and s390 as well. Otherwise the build will
> > break with CONFIG_VIRT_CPU_ACCOUNTING=y on these architectures once the
> > new primitive is used.
> >
> 
> But, those archs have arch specific cputime as well and so need a
> different macro for nsecs_to_cputime64, instead of nsec_to_jiffies64.
> Right? As of now this new primitive should not be used in those archs.
> I guess this is something needed when using the primitive in future?

Yes on both parts of the question. You need an independent
implementation of the nsecs_to_cputime64 primitive for the architectures
that have their own definition of cputime and this definition will be
needed when the primitive is used is the future.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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