Re: [PATCH] jump_label: jump_label for boot options.

From: Mike Galbraith
Date: Fri Dec 02 2011 - 00:34:17 EST


On Fri, 2011-12-02 at 09:28 +0900, KAMEZAWA Hiroyuki wrote:
> On Thu, 1 Dec 2011 10:40:36 -0500
> Jason Baron <jbaron@xxxxxxxxxx> 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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