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From: Boqun Feng <boqun.feng@gmail.com>
To: Qian Cai <cai@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Waiman Long <longman@redhat.com>
Subject: Re: [RFC v7 11/19] lockdep: Fix recursive read lock related safe->unsafe detection
Date: Thu, 17 Sep 2020 09:53:39 +0800	[thread overview]
Message-ID: <20200917015339.GE127490@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net> (raw)
In-Reply-To: <607c446bc8d3a0cc6e96aa9792e075913ad6b2c6.camel@redhat.com>

On Wed, Sep 16, 2020 at 05:11:59PM -0400, Qian Cai wrote:
> On Thu, 2020-09-17 at 00:14 +0800, Boqun Feng wrote:
> > Found a way to resolve this while still keeping the BFS. Every time when
> > we want to enqueue a lock_list, we basically enqueue a whole dep list of
> > entries from the previous lock_list, so we can use a trick here: instead
> > enqueue all the entries, we only enqueue the first entry and we can
> > fetch other silbing entries with list_next_or_null_rcu(). Patch as
> > below, I also took the chance to clear the code up and add more
> > comments. I could see this number (in /proc/lockdep_stats):
> > 
> > 	max bfs queue depth:                   201
> > 
> > down to (after apply this patch)
> > 
> > 	max bfs queue depth:                   61
> > 
> > with x86_64_defconfig along with lockdep and selftest configs.
> > 
> > Qian, could you give it a try?
> 
> It works fine as the number went down from around 3000 to 500 on our workloads.
> 

Thanks, let me send a proper patch. I will add a Reported-by tag from
you.

Regards,
Boqun

  reply	other threads:[~2020-09-17  2:03 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-07  7:42 [RFC v7 00/19] lockdep: Support deadlock detection for recursive read locks Boqun Feng
2020-08-07  7:42 ` [RFC v7 01/19] locking: More accurate annotations for read_lock() Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 02/19] lockdep/Documention: Recursive read lock detection reasoning Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 03/19] lockdep: Demagic the return value of BFS Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 04/19] lockdep: Make __bfs() visit every dependency until a match Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 05/19] lockdep: Reduce the size of lock_list::distance Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 06/19] lockdep: Introduce lock_list::dep Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 07/19] lockdep: Extend __bfs() to work with multiple types of dependencies Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 08/19] lockdep: Make __bfs(.match) return bool Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 09/19] lockdep: Support deadlock detection for recursive read locks in check_noncircular() Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 10/19] lockdep: Adjust check_redundant() for recursive read change Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 11/19] lockdep: Fix recursive read lock related safe->unsafe detection Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-09-15 18:32   ` [RFC v7 11/19] " Qian Cai
2020-09-16  8:10     ` Boqun Feng
2020-09-16 16:14       ` Boqun Feng
2020-09-16 21:11         ` Qian Cai
2020-09-17  1:53           ` Boqun Feng [this message]
2020-08-07  7:42 ` [RFC v7 12/19] lockdep: Add recursive read locks into dependency graph Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-09-14 18:16   ` [RFC v7 12/19] " Qian Cai
2020-09-14 22:04     ` Qian Cai
2020-08-07  7:42 ` [RFC v7 13/19] lockdep/selftest: Add a R-L/L-W test case specific to chain cache behavior Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 14/19] lockdep: Take read/write status in consideration when generate chainkey Boqun Feng
2020-08-21 17:41   ` Peter Zijlstra
2020-08-22  2:52     ` boqun.feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 15/19] lockdep/selftest: Unleash irq_read_recursion2 and add more Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 16/19] lockdep/selftest: Add more recursive read related test cases Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 17/19] Revert "locking/lockdep/selftests: Fix mixed read-write ABBA tests" Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 18/19] locking/selftest: Add test cases for queued_read_lock() Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-07  7:42 ` [RFC v7 19/19] lockdep/selftest: Introduce recursion3 Boqun Feng
2020-08-27  7:54   ` [tip: locking/core] " tip-bot2 for Boqun Feng
2020-08-21 19:56 ` [RFC v7 00/19] lockdep: Support deadlock detection for recursive read locks Peter Zijlstra
2020-08-23  1:12   ` boqun.feng

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