linux-kernel - Re: [PATCH] PM / arch: x86: Rework the MSR_IA32_ENERGY_PERF

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Date:   Thu, 21 Mar 2019 08:58:07 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
        Len Brown <len.brown@...el.com>,
        Linux PM <linux-pm@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Laura Abbott <labbott@...oraproject.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Simon Schricker <sschricker@...e.de>,
        Borislav Petkov <bp@...e.de>, Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH] PM / arch: x86: Rework the MSR_IA32_ENERGY_PERF_BIAS
 handling

On Thu, Mar 21, 2019 at 01:00:52AM +0100, Rafael J. Wysocki wrote:
> + * The Performance and Energy Bias Hint (EPB) allows software to specify its
> + * preference with respect to the power-performance tradeoffs present in the
> + * processor.  Generally, the EPB is expected to be set by user space through
> + * the generic MSR interface (with the help of the x86_energy_perf_policy tool),
> + * but there are two reasons for the kernel to touch it.

So I hate /dev/msr with a passion. It is absolute atrocious crap.

Please, just make a real interface for this if it is important.