From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
Bart Van Assche <bvanassche@acm.org>
Subject: Re: [PATCH 4/5] locking/lockdep: Reuse free chain_hlocks entries
Date: Fri, 13 Dec 2019 15:08:51 -0500 [thread overview]
Message-ID: <2763959e-b0e9-a8cd-3468-232d128c8260@redhat.com> (raw)
In-Reply-To: <20191213184759.GH2844@hirez.programming.kicks-ass.net>
On 12/13/19 1:47 PM, Peter Zijlstra wrote:
> On Fri, Dec 13, 2019 at 01:35:05PM -0500, Waiman Long wrote:
>> On 12/13/19 1:12 PM, Peter Zijlstra wrote:
>>>> In this way, the wasted space will be k bytes where k is the number of
>>>> 1-entry chains. I don't think merging adjacent blocks will be that
>>>> useful at this point. We can always add this capability later on if it
>>>> is found to be useful.
>>> I'm thinking 1 entry isn't much of a chain. My brain is completely fried
>>> atm, but are we really storing single entry 'chains' ? It seems to me we
>>> could skip that.
>>>
>> Indeed, the current code can produce a 1-entry chain. I also thought
>> that a chain had to be at least 2 entries. I got tripped up assuming
>> that. It could be a bug somewhere that allow a 1-entry chain to happen,
>> but I am not focusing on that right now.
> If we need the minimum 2 entry granularity, it might make sense to spend
> a little time on that. If we can get away with single entry markers,
> then maybe write a comment so we'll not forget about it.
>
I will take a look at why an 1-entry chain happes and see if it is a bug
that need to be fixed.
Cheers,
Longman
next prev parent reply other threads:[~2019-12-13 20:41 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-12 22:35 [PATCH 0/5] locking/lockdep: Reuse zapped chain_hlocks entries Waiman Long
2019-12-12 22:35 ` [PATCH 1/5] locking/lockdep: Track number of zapped classes Waiman Long
2019-12-12 22:35 ` [PATCH 2/5] locking/lockdep: Track leaked chain_hlocks entries Waiman Long
2019-12-12 22:35 ` [PATCH 3/5] locking/lockdep: Track number of zapped lock chains Waiman Long
2019-12-12 22:35 ` [PATCH 4/5] locking/lockdep: Reuse free chain_hlocks entries Waiman Long
2019-12-13 10:25 ` Peter Zijlstra
2019-12-13 10:50 ` Peter Zijlstra
2019-12-13 16:02 ` Waiman Long
2019-12-13 16:05 ` Waiman Long
2019-12-13 18:12 ` Peter Zijlstra
[not found] ` <7ca26a9a-003f-6f24-08e4-f01b80e3e962@redhat.com>
2019-12-13 18:47 ` Peter Zijlstra
2019-12-13 20:08 ` Waiman Long [this message]
2019-12-15 17:06 ` Waiman Long
2019-12-13 15:02 ` Waiman Long
2019-12-13 18:43 ` Peter Zijlstra
2019-12-12 22:35 ` [PATCH 5/5] locking/lockdep: Decrement irq context counters when removing lock chain Waiman Long
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