linux-kernel - Re: [PATCH 1/1] ARM: oprofile: add A5/A7/A15 entries in op_perf

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Message-ID: <20121120170601.GR2504@rric.localhost>
Date:	Tue, 20 Nov 2012 18:06:01 +0100
From:	Robert Richter <rric@...nel.org>
To:	Will Deacon <will.deacon@....com>
Cc:	Maynard Johnson <maynardj@...ibm.com>,
	"jgq516@...il.com" <jgq516@...il.com>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"oprofile-list@...ts.sf.net" <oprofile-list@...ts.sf.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/1] ARM: oprofile: add A5/A7/A15 entries in op_perf_name

On 20.11.12 16:55:17, Will Deacon wrote:
> On Tue, Nov 20, 2012 at 04:31:58PM +0000, Robert Richter wrote:
> > I am thinking of the following:
> > 
> >  # cat /root/cpu_type
> >  arm/armv7-ca5
> >  # cat /dev/oprofile/cpu_type
> >  unknown
> >  # mount --bind /root/cpu_type /dev/oprofile/cpu_type
> >  # cat /dev/oprofile/cpu_type
> >  arm/armv7-ca5
> > 
> > From here legacy oprofile tools work as expected using oprofilefs. (I
> > think. Did not test it.) We need to change the kernel for this a bit
> > to return 'unknown'. The mount could be done by the oprofile tools
> > using existing cpu detection code. This is only one way to setup
> > cpu_type from userland, there could be other ways too.
> 
> Ok, this is functionally equivalent to the patch that was submitted at the
> start of this thread: it solves the problem of mapping a single ARM core to
> a oprofile's CPU ID string. Technically, I don't mind doing that in the
> kernel (at least, it means you don't need to do your trick above)

The advantage of a solution where userland updates cpu_type is that we
never need to update the kernel anymore. This means, cpu detection can
be part of the tools.

-Robert
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