linux-kernel - Re: [PATCH] lockdep: do not count lock class operations without CONFIG_DEBUG

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Message-ID: <20170519090910.fubv3c3ozfckavi3@hirez.programming.kicks-ass.net>
Date:   Fri, 19 May 2017 11:09:10 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] lockdep: do not count lock class operations without
 CONFIG_DEBUG_LOCKDEP

On Fri, May 19, 2017 at 10:06:01AM +0300, Konstantin Khlebnikov wrote:
> Currently this counter shown in /proc/lockdep if CONFIG_DEBUG_LOCKDEP=y
> This patch disables it completely if this option is disabled.
> 
> This counter might be useful for debugging lockdep itself, but for normal
> debugging it seems useless. Lockstat provides more detailed statistics.
> 
> This atomic_inc is a hot spot inside __lock_acquire() for debug kernel.
> 
> With patch "netperf -H localhost" shows some boost: 2500 -> 2600

Nothing against these patches, but I do wonder why you're performance
optimizing debug kernels ;-)