netdev - Re: [RFC PATCH 0/8] Introduce simple hazard pointers for lockdep

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Message-ID: <Z/+7LMnQqtV+mnJ+@gmail.com>
Date: Wed, 16 Apr 2025 07:14:04 -0700
From: Breno Leitao <leitao@...ian.org>
To: Boqun Feng <boqun.feng@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
	aeh@...a.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	edumazet@...gle.com, jhs@...atatu.com, kernel-team@...a.com,
	Erik Lundgren <elundgren@...a.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Uladzislau Rezki <urezki@...il.com>, rcu@...r.kernel.org
Subject: Re: [RFC PATCH 0/8] Introduce simple hazard pointers for lockdep

Hi Boqun,

On Sun, Apr 13, 2025 at 11:00:47PM -0700, Boqun Feng wrote:

> Overall it looks promising to me, but I would like to see how it
> performs in the environment of Breno. Also as Paul always reminds me:
> buggy code usually run faster, so please take a look in case I'm missing
> something ;-) Thanks!

Thanks for the patchset. I've confirmed that the wins are large on my
environment, but, at the same magnitute of synchronize_rcu_expedited().

Here are the numbers I got:

	6.15-rc1 (upstream)
		# time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq
		real	0m3.986s
		user	0m0.001s
		sys	0m0.093s

	Your patchset on top of 6.15-rc1
		# time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq
		real	0m0.072s
		user	0m0.001s
		sys	0m0.070s


	My original proposal of using synchronize_rcu_expedited()[1]
		# time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1234: mq
		real	0m0.074s
		user	0m0.001s
		sys	0m0.061s

Link: https://lore.kernel.org/all/20250321-lockdep-v1-1-78b732d195fb@debian.org/ [1]

Thanks for working on it,
--breno