linux-kernel - Re: [RFC 2/2] Introduce sysctl(s) for the migration costs

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Message-ID: <1518148447.24350.34.camel@gmx.de>
Date:   Fri, 09 Feb 2018 04:54:07 +0100
From:   Mike Galbraith <efault@....de>
To:     Rohit Jain <rohit.k.jain@...cle.com>, linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...hat.com, steven.sistare@...cle.com,
        joelaf@...gle.com, jbacik@...com, riel@...hat.com,
        juri.lelli@...hat.com, dhaval.giani@...cle.com
Subject: Re: [RFC 2/2] Introduce sysctl(s) for the migration costs

On Thu, 2018-02-08 at 14:19 -0800, Rohit Jain wrote:
> This patch introduces the sysctl for sched_domain based migration costs.
> These in turn can be used for performance tuning of workloads.

With this patch, we trade 1 completely bogus constant (cost is really
highly variable) for 3, twiddling of which has zero effect unless you
trigger a domain rebuild afterward, which is neither mentioned in the
changelog, nor documented.

bogo-numbers++ is kinda hard to love.

	-Mike