linux-kernel - Re: [PATCH 4/4] arm: dts: r8a7790: add cpu capacity-dmips-mhz information

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] [day] [month] [year] [list]

Message-ID: <a0099e02-096c-f8e0-0380-ecb9549f20b4@arm.com>
Date:   Mon, 9 Oct 2017 18:55:07 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Simon Horman <horms@...ge.net.au>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-renesas-soc@...r.kernel.org,
        Russell King <linux@...linux.org.uk>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@....com>
Subject: Re: [PATCH 4/4] arm: dts: r8a7790: add cpu capacity-dmips-mhz
 information

On 18/09/17 08:39, Simon Horman wrote:
> On Wed, Aug 30, 2017 at 03:41:20PM +0100, Dietmar Eggemann wrote:
>> The following 'capacity-dmips-mhz' dt property values are used:
>>
>> Cortex-A15: 1024, Cortex-A7: 539
>>
>> They have been derived form the cpu_efficiency values:
>>
>> Cortex-A15: 3891, Cortex-A7: 2048
>>
>> by scaling them so that the Cortex-A15s (big cores) use 1024.
>>
>> The cpu_efficiency values were originally derived from the "Big.LITTLE
>> Processing with ARM Cortex™-A15 & Cortex-A7" white paper
>> (http://www.cl.cam.ac.uk/~rdm34/big.LITTLE.pdf). Table 1 lists 1.9x
>> (3891/2048) as the Cortex-A15 vs Cortex-A7 performance ratio for the
>> Dhrystone benchmark.
>>
>> The following platform is affected once cpu-invariant accounting
>> support is re-connected to the task scheduler:
> 
> Thanks, applied for v4.15.
> 
> My understanding from the following comment in the cover letter is that not
> currently the case and this there is no behavioural change in applying this
> patch.
> 
> For the record I observed the following with and without this patch
> applied. I believe this is the expected result.
> 
> v4.14-rc1
> # cat /sys/devices/system/cpu/cpu*/cpu_capacity
> 1535
> 1535
> 1535
> 1535
> 1024
> 1024
> 1024
> 1024
> 
> v4.14-rc1 + patch
> # cat /sys/devices/system/cpu/cpu*/cpu_capacity
> 1024
> 1024
> 1024
> 1024
> 539
> 539
> 539
> 539

Thanks Simon! Yes, that is the expected behaviour. And sorry for not
responding earlier!

With exynos542{0,2} and r8a7790 switching to the 'capacity-dmips-mhz'
based solution in v4.15, I can push for removal of the cpu_efficency
code [patch 1/4].