From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Galbraith <umgwanakikbuti-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 3/3] sched: Implement interface for cgroup unified
 hierarchy
Date: Wed, 19 Aug 2015 05:23:40 +0200
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To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, kernel-team <kernel-team-b10kYP2dOMg@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>

On Tue, 2015-08-18 at 13:31 -0700, Tejun Heo wrote:

> So, this is a trade-off we're consciously making.  If there are
> common-enough use cases which require jumping across different cgroup
> domains, we'll try to figure out a way to accomodate those but by
> default migration is a very cold and expensive path.

Hm.  I know of a big data outfit to which attach/detach performance was
important enough for them to have plucked an old experimental overhead
reduction hack (mine) off lkml, and shipped it.  It must have mattered a
LOT for them (not suicidal crash test dummies) to have done that.

	-Mike