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Re: [PATCH] lockdep: do not count lock class operations without CONFIG_DEBUG_LOCKDEP

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH] lockdep: do not count lock class operations without CONFIG_DEBUG_LOCKDEP
Date 2017-05-19 11:10 +0200
Message-ID <tIM55-8nS-39@gated-at.bofh.it> (permalink)
References <tIKcW-76X-5@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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 ;-)

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[PATCH] lockdep: do not count lock class operations without  CONFIG_DEBUG_LOCKDEP Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2017-05-19 09:10 +0200
  Re: [PATCH] lockdep: do not count lock class operations without  CONFIG_DEBUG_LOCKDEP Peter Zijlstra <peterz@infradead.org> - 2017-05-19 11:10 +0200
    Re: [PATCH] lockdep: do not count lock class operations without  CONFIG_DEBUG_LOCKDEP Konstantin Khlebnikov <khlebnikov@yandex-team.ru> - 2017-05-19 11:30 +0200

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