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From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	Yang Shi <yang.shi@linux.alibaba.com>,
	Arnd Bergmann <arnd@arndb.de>,
	chuhu@redhat.com
Subject: Re: [PATCH v2 2/2] debugobjects: Disable lockdep tracking of debugobjects internal locks
Date: Fri, 28 Sep 2018 14:33:40 -0400	[thread overview]
Message-ID: <52e6048f-c361-e6bc-7840-a55bbd30416f@redhat.com> (raw)
In-Reply-To: <e6dc78dc-fdd5-81b7-9a6a-c3e0f02286cc@redhat.com>

On 09/25/2018 12:36 PM, Waiman Long wrote:
> On 09/25/2018 12:31 PM, Peter Zijlstra wrote:
>> Also, where is the performance benefit here. The normal lock_acquire
>> path doesn't change gobal state (it will not see new lock ordering in
>> 99%+ of the cases).
>>
>> Typically we only push the lock on the task local lock stack, compute
>> the new hash, and do the hash lookup, find it already exists and return.
>>
>> So what is the expensive part, and can we do something about that?
> I will need to do some experimentation to find out. Will update this
> thread with my finding.
>

I have sent out a patchset on improving lockdep performance that
hopefully will help to alleviate the problems that I saw. I still have
other ideas about further changes I want to investigate, but that will
wait until I am done with the current lockdep patchset.

-Longman


      reply	other threads:[~2018-09-28 18:33 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-25 14:41 [PATCH v2 0/2] debugobjects: Fix potential hard lockup by disabling lockdep Waiman Long
2018-09-25 14:41 ` [PATCH v2 1/2] locking/lockdep: Don't warn class/lock name mismatch for novalidate class Waiman Long
2018-09-25 14:41 ` [PATCH v2 2/2] debugobjects: Disable lockdep tracking of debugobjects internal locks Waiman Long
2018-09-25 15:32   ` Peter Zijlstra
2018-09-25 16:20     ` Waiman Long
2018-09-25 16:31       ` Peter Zijlstra
2018-09-25 16:36         ` Waiman Long
2018-09-28 18:33           ` Waiman Long [this message]

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