linux-kernel - Re: [RFC PATCH 0/4] Add hazard pointers to kernel

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Message-ID: <Zuwx409kgivi1G5T@infradead.org>
Date: Thu, 19 Sep 2024 07:14:59 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org,
	rcu@...r.kernel.org, linux-mm@...ck.org, lkmm@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Vlastimil Babka <vbabka@...e.cz>, maged.michael@...il.com
Subject: Re: [RFC PATCH 0/4] Add hazard pointers to kernel

On Wed, Sep 18, 2024 at 09:18:43AM +0200, Linus Torvalds wrote:
> On Tue, 17 Sept 2024 at 16:34, Boqun Feng <boqun.feng@...il.com> wrote:
> >
> > This series introduces hazard pointers [1] to kernel space. A TL;DR
> > description of hazard pointers is "a scalable refcounting mechanim
> > with RCU-like API". More information can be found at [2].
> 
> Please give actual "this is useful for X, and here is an actual real
> load with numbers showing why it matters".

Agreed.  From the description this would seem like a good fit for
q_usage_counter in the block layer, which currently makes creative use
of percpu counters.