Message-ID: <55929834.8090800@redhat.com>
Date: Tue, 30 Jun 2015 09:23:00 -0400
From: Prarit Bhargava <prarit@redhat.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@amacapital.net>,
        Ingo Molnar <mingo@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        X86 ML <x86@kernel.org>, Len Brown <len.brown@intel.com>,
        Dasaratharaman Chandramouli 
	<dasaratharaman.chandramouli@intel.com>,
        Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, Brian Gerst <brgerst@gmail.com>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
        Matt Fleming <matt@codeblueprint.co.uk>
Subject: Re: [PATCH] x86, msr: Allow read access to /dev/cpu/X/msr
References: <1435341131-3279-1-git-send-email-prarit@redhat.com> <20150627083354.GA12834@gmail.com> <20150627083921.GA13074@gmail.com> <CALCETrXpiMWwiAfbxcKTDYCewrwq-UTwLV+xXTxdOkd+B3G-OQ@mail.gmail.com> <559005DD.3070003@redhat.com> <5591A1D3.6010003@zytor.com> <559289A7.3040500@redhat.com> <20150630124426.GD12596@twins.programming.kicks-ass.net>
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On 06/30/2015 08:44 AM, Peter Zijlstra wrote:
> On Tue, Jun 30, 2015 at 08:20:55AM -0400, Prarit Bhargava wrote:
>> it seems like visiting changes on each of these packages (and the other
>> packages that I'm sure I've missed) will be moderately difficult.
>>
>> Thoughts?
> 
> Start by changing the ones users want to run most and leave the rest
> requiring root privs until someone has the time to convert them.
> 
> Its not like we can remove the msr driver any time soon anyway.
> 

Yes, I agree.

> So I would suggest starting with the perf MSR driver thingy for all
> those MSRs that count things and see if you can convert say
> turbostat/cpufrequtils/powertop over to that.

Yep, that was my plan -- I'm going to do the in-tree utilities first then look
at the external programs.

> 
> I suspect there's MSR that are useful to expose but are not counting,
> I'm not sure perf is the right interface for those.
> 
> Making an inventory on which MSRs are required by these tools and what
> kind of data they provide might give a good idea on how to continue.
> 
> If most of these tools only use counting MSRs that can be serviced with
> the perf-msr driver then that would be great.
> 

Thanks Peter!

P.
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