linux-kernel - Re: [PATCH 0/3] condition EAS enablement on FI support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20200924133727.GB3920949@google.com>
Date:   Thu, 24 Sep 2020 14:37:27 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        catalin.marinas@....com, will@...nel.org, rjw@...ysocki.net,
        viresh.kumar@...aro.org, dietmar.eggemann@....com,
        valentin.schneider@....com, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] condition EAS enablement on FI support

On Thursday 24 Sep 2020 at 13:39:34 (+0100), Ionela Voinescu wrote:
> Given the maturity gained by cpufreq-based Frequency Invariance (FI)
> support following the patches at [1], this series conditions Energy
> Aware Scheduling (EAS) enablement on a frequency invariant system.
> 
> Currently, EAS can be enabled on a system without FI support, leading
> to incorrect (energy-wise) task placements. As no warning is emitted,
> it could take some debugging effort to track the behavior back to the
> lack of FI support; this series changes that by disabling EAS
> (and advertising it) when FI support is missing.
> 
> The series is structured as follows:
>  - 1/3 - create function that can rebuild the scheduling and EAS'
>    performance domains if EAS' initial conditions change
>  - 2/3 - condition EAS enablement on FI support
>  - 3/3 - arm64: rebuild scheduling and performance domains in the
>          case of late, counter-driven FI initialisation.

I'm still reading through this, but shouldn't patch 2 and 3 be swapped?
Otherwise we have a weird state at patch 2 where EAS will fail to start
(IIUC), which might not be ideal for bisection.

Thoughts?

Cheers,
Quentin