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

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Message-ID: <20160923071246.GJ2794@worktop>
Date:   Fri, 23 Sep 2016 09:12:46 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Babu Moger <babu.moger@...cle.com>
Cc:     mingo@...hat.com, akpm@...ux-foundation.org, keescook@...omium.org,
        dan.j.williams@...el.com, aryabinin@...tuozzo.com, tj@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Ajust lockdep static allocations

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.