Re: [PATCH 0/2] Ajust lockdep static allocations

[Babu Moger]

On 9/23/2016 9:34 AM, Peter Zijlstra wrote:
> On Fri, Sep 23, 2016 at 09:04:42AM -0500, Babu Moger wrote:
> > On 9/23/2016 2:12 AM, Peter Zijlstra wrote:
> > > On Thu, Sep 22, 2016 at 11:43:34AM -0700, Babu Moger wrote:
> > > > These patches adjust the static allocations for lockdep
> > > > data structures used for debugging locking correctness. The current
> > > > code reserves about 4MB extra space for these data structures. Most
> > > > of the configurations do not need these many data structures. While
> > > > testing, I have not seen it go beyond 20% of already reserved entries.
> > > >
> > > > $grep "lock-classes" /proc/lockdep_stats
> > > > 	lock-classes:                          1560 [max: 8191]
> > > >
> > > > Reserving even more space seems unreasonable. So, keeping the default
> > > > entries small as before the Commit 1413c0389333 ("lockdep: Increase static
> > > > allocations"). Added new CONFIG_PROVE_LOCKING_PLUS in case someone
> > > > needs more entries to debug their large configuration.
> > > Why make this more complicated? There's absolutely no upside to this
> > > change as far as I can see.
> > Peter, What do you mean?
> I mean I see no point to the patches you send.
>
> > Revert the commit 1413c038933?
> Nah, why would I?
>
> > Right now, I cannot boot my setup after enabling lockdep. How do you
> > think we can handle this?
> Why can't you boot? You have that little memories? 4MB doesn't seem like
> a worthwhile amount of memory.
>
> Also, you didn't say.  This seems a somewhat crucial point.

    Correct, We can't boot with lockdep. Sorry I did not make that 
clear.  We have a limit on static size of the kernel.

> In any case, maybe invert this, add make it depend on CONFIG_BASE_SMALL,
> since this really only matters for really dinky systems.
     Sure. Will  use  CONFIG_BASE_SMALL and re-post the patches. Thanks
>