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

From	Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Newsgroups	linux.kernel
Subject	Re: [PATCH] lockdep: do not count lock class operations without CONFIG_DEBUG_LOCKDEP
Date	2017-05-19 11:30 +0200
Message-ID	<tIMoq-8v4-13@gated-at.bofh.it> (permalink)
References	<tIKcW-76X-5@gated-at.bofh.it> <tIM55-8nS-39@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 19.05.2017 12:09, Peter Zijlstra wrote:
> 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 ;-)
> 

Performance of debug features matters too
Obviously this saves time and money for massive testing

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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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