linux-kernel - Re: [PATCH] lockdep: increase static allocations

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Message-ID: <20140108232322.GH20765@two.firstfloor.org>
Date:	Thu, 9 Jan 2014 00:23:22 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Andi Kleen <andi@...stfloor.org>, peterz@...radead.org,
	mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lockdep: increase static allocations

On Wed, Jan 08, 2014 at 03:10:55PM -0500, Sasha Levin wrote:
> On 01/08/2014 02:51 PM, Andi Kleen wrote:
> >Sasha Levin <sasha.levin@...cle.com> writes:
> >
> >>Fuzzing a recent kernel with a large configuration hits the static
> >>allocation limits and disables lockdep.
> >
> >Doesn't that use a lot more memory?  I thought lockdep preallocates.
> >
> >Doubling may be too aggressive.
> 
> The patch adds about 4MB of memory usage, I didn't think it's too much for something
> that is only enabled during debugging.

Wasting 4MB is an issue.

Linus' first Linux system had less total memory than that.

> 
> If this is an issue, can I suggest making these values configurable in the .config
> and just let users pick whatever they want?

Better allocate it at boot time, using a boot parameter or somesuch.

-Andi
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