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Date:   Tue, 12 Jan 2021 16:01:06 +0100
From:   Peter Zijlstra <>
To:     "Rafael J. Wysocki" <>
Cc:     Linux PM <>,
        LKML <>,
        x86 Maintainers <>,
        Srinivas Pandruvada <>,
        Giovanni Gherdovich <>,
        Giovanni Gherdovich <>
Subject: Re: [PATCH] x86: PM: Register syscore_ops for scale invariance

On Fri, Jan 08, 2021 at 07:05:59PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <>
> On x86 scale invariace tends to be disabled during resume from
> suspend-to-RAM, because the MPERF or APERF MSR values are not as
> expected then due to updates taking place after the platform
> firmware has been invoked to complete the suspend transition.
> That, of course, is not desirable, especially if the schedutil
> scaling governor is in use, because the lack of scale invariance
> causes it to be less reliable.
> To counter that effect, modify init_freq_invariance() to register
> a syscore_ops object for scale invariance with the ->resume callback
> pointing to init_counter_refs() which will run on the CPU starting
> the resume transition (the other CPUs will be taken care of the
> "online" operations taking place later).
> Fixes: e2b0d619b400 ("x86, sched: check for counters overflow in frequency invariant accounting")
> Signed-off-by: Rafael J. Wysocki <>

Thanks!, I'll take it through the sched/urgent tree?

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