linux-kernel - Re: [PATCH v4 07/10] sched/topology: Add more flags to the SD degeneration mask

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Message-ID: <20200806135734.GB2077896@gmail.com>
Date:   Thu, 6 Aug 2020 15:57:34 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        morten.rasmussen@....com, Quentin Perret <qperret@...gle.com>
Subject: Re: [PATCH v4 07/10] sched/topology: Add more flags to the SD
 degeneration mask


* Valentin Schneider <valentin.schneider@....com> wrote:

> I don't think it is going to change much in practice, but we were missing
> those:
> 
> o SD_BALANCE_WAKE: Used just like the other SD_BALANCE_* flags, so also
>   needs > 1 group.
> o SD_ASYM_PACKING: Hinges on load balancing (periodic / wakeup), thus needs
>   > 1 group to happen
> o SD_OVERLAP: Describes domains with overlapping groups; can't have
>   overlaps with a single group.
> 
> SD_PREFER_SIBLING is as always the odd one out: we currently consider it
> in sd_parent_degenerate() but not in sd_degenerate(). It too hinges on load
> balancing, and thus won't have any effect when set on a domain with a
> single group. Add it to the sd_degenerate() groups mask.

Would be nice to add these one by one, just in case there's a 
performance or boot regression with any of them.

Thanks,

	Ingo