linux-kernel - Re: [PATCH] jump_label: jump

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Date:	Fri, 02 Dec 2011 06:34:05 +0100
From:	Mike Galbraith <efault@....de>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Jason Baron <jbaron@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	rostedt@...dmis.org
Subject: Re: [PATCH] jump_label: jump_label for boot options.

On Fri, 2011-12-02 at 09:28 +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 1 Dec 2011 10:40:36 -0500
> Jason Baron <jbaron@...hat.com> wrote:
> 
> > On Thu, Dec 01, 2011 at 11:53:53AM +0900, KAMEZAWA Hiroyuki wrote:
> > > I tried to use jump_label for handling memcg's boot options which sets
> > > global variable true/false and never changes after boot. And found jump_table
> > > is larger than expected. This patch is a trial to allow to place jump_table
> > > in .init section. How do you think ?
> > > 
> > 
> > Remeber too, that 'static_branch()' is inherently biased. That is, the
> > 'false' path is assumed to be the the most likely path. Thus, the 'true'
> > path is move out-of-line. Thus, if the 'true' branch is potentially
> > used all the time, we would want to make sure that the savings of not
> > having to check a variable is still worth it. I should probably rename
> > static_branch() -> 'static_branch_default_false()' to make that clear.
> > 
> Thank you for pointing out.
> 
> My assumption is that it's disabled at boot by few people because sane
> people will not config memcg if they don't want. Most of distro users
> will not turn off it...

I think that's a bad assumption.  I see a lot of cgroup_disable=memory
command lines, and _always_ add it to grub when installing "everything
plus the kitchen sink" distro kernels on my boxen. 

	-Mike

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