linux-kernel - RE: [PATCH v2 2/3] Documentation, ABI: Add a document entry for cache id

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Date:	Fri, 8 Jul 2016 17:06:46 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	"Anvin, H Peter" <h.peter.anvin@...el.com>,
	Ingo Molnar <mingo@...e.hu>, Borislav Petkov <bp@...e.de>,
	"Luck, Tony" <tony.luck@...el.com>,
	Stephane Eranian <eranian@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	"Shankar, Ravi V" <ravi.v.shankar@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: RE: [PATCH v2 2/3] Documentation, ABI: Add a document entry for
 cache id

> From: Ingo Molnar [mailto:mingo.kernel.org@...il.com] On Behalf Of Ingo
> Molnar
> Sent: Friday, July 08, 2016 1:42 AM
> * Fenghua Yu <fenghua.yu@...el.com> wrote:
> 
> > From: Fenghua Yu <fenghua.yu@...el.com>
> >
> > Add an ABI document entry for
> /sys/devices/system/cpu/cpu*/cache/index*/id.
> >
> > Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> > ---
> >  Documentation/ABI/testing/sysfs-devices-system-cpu | 13
> +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu
> b/Documentation/ABI/testing/sysfs-devices-system-cpu
> > index 1650133..cc62034 100644
> > --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
> > +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
> > @@ -272,6 +272,19 @@ Description:	Parameters for the CPU cache
> attributes
> >  				     the modified cache line is written to main
> >  				     memory only when it is replaced
> >
> > +
> > +What:		/sys/devices/system/cpu/cpu*/cache/index*/id
> > +Date:		July 2016
> > +Contact:	Linux kernel mailing list <linux-kernel@...r.kernel.org>
> > +Description:	Cache id
> > +
> > +		The id identifies a cache in the platform. In same index, the id
> > +		is unique across the platform.
> 
> What does 'In same index' mean?

It means one cache's id is unique in all caches with same cache index number. For example, in all caches with index3 (i.e. level3), cache id 0 is unique to identify a L3 cache. But in caches with index 0 (i.e. Level0), there is also a cache id 0. So cache id is unique in one index. But not unique in two different index.

Does that make sense? I hope I express that correctly.

Thanks.

-Fenghua