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From: Wanpeng Li <kernellwp@gmail.com>
Date: Wed, 17 Aug 2016 17:26:26 +0800
Message-ID: <CANRm+Cw14tk7vg9cjW6PVEVK47N-Uwk3e5-=LtRLv8wr_u4zLg@mail.gmail.com>
Subject: Re: [PATCH v3 05/13] sched: Introduce SD_ASYM_CPUCAPACITY
 sched_domain topology flag
To: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Yuyang Du <yuyang.du@intel.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Mike Galbraith <mgalbraith@suse.de>, sgurrappadi@nvidia.com,
        Koan-Sin Tan <freedom.tan@mediatek.com>,
        =?UTF-8?B?5bCP5p6X5pWs5aSq?= <keita.kobayashi.ym@renesas.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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2016-08-17 17:23 GMT+08:00 Morten Rasmussen <morten.rasmussen@arm.com>:
> On Wed, Aug 17, 2016 at 04:42:36PM +0800, Wanpeng Li wrote:
>> 2016-07-25 21:34 GMT+08:00 Morten Rasmussen <morten.rasmussen@arm.com>:
>> > Add a topology flag to the sched_domain hierarchy indicating the lowest
>> > domain level where the full range of cpu capacities is represented by
>> > the domain members for asymmetric capacity topologies (e.g. ARM
>> > big.LITTLE).
>> >
>> > The flag is intended to indicate that extra care should be taken when
>> > placing tasks on cpus and this level spans all the different types of
>> > cpus found in the system (no need to look further up the domain
>> > hierarchy). This information is currently only available through
>> > iterating through the capacities of all the cpus at parent levels in the
>> > sched_domain hierarchy.
>> >
>> > SD 2      [  0      1      2      3]  SD_ASYM_CPUCAPACITY
>> >
>> > SD 1      [  0      1] [   2      3]  !SD_ASYM_CPUCAPACITY
>> >
>> > cpu:         0      1      2      3
>> > capacity:  756    756   1024   1024
>> >
>> > If the topology in the example above is duplicated to create an eight
>> > cpu example with third sched_domain level on top (SD 3), this level
>> > should not have the flag set (!SD_ASYM_CPUCAPACITY) as its two group
>> > would both have all cpu capacities represented within them.
>>
>> I didn't find the place where set SD_ASYM_CPUCAPACITY to any SDs in
>> this patchset, but you have testing result in cover letter, where I
>> miss?
>
> The flag is supposed to be set by arch-specific code. I included a few
> patches in v1 and v2 that set the flag for arch/arm. However, since they
> are hopefully soon to be superseded by patches from Juri I dropped them
> from the v3 posting and provided a pointer to branch containing this patch
> set, Juri's patches, and few additional glue patches instead that
> enabled the flag when necessary for arch/arm and arch/arm64.

Ah, ok, thanks for the information. :)

Regards,
Wanpeng Li