Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 28 Jul 2021 13:47:20 -0700
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Josh Triplett <josh@joshtriplett.org>
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com,
        akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
        tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org,
        dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com,
        oleg@redhat.com, joel@joelfernandes.org,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH v2 rcu 04/18] rcu: Weaken ->dynticks accesses and updates
Message-ID: <20210728204720.GN4397@paulmck-ThinkPad-P17-Gen-1>
Reply-To: paulmck@kernel.org
References: <20210721202042.GA1472052@paulmck-ThinkPad-P17-Gen-1>
 <20210721202127.2129660-4-paulmck@kernel.org>
 <20210728173715.GA9416@paulmck-ThinkPad-P17-Gen-1>
 <YQG//899pPl2JIWw@localhost>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YQG//899pPl2JIWw@localhost>
Precedence: bulk

On Wed, Jul 28, 2021 at 01:37:19PM -0700, Josh Triplett wrote:
> On Wed, Jul 28, 2021 at 10:37:15AM -0700, Paul E. McKenney wrote:
> > This change makes the memory ordering requirements
> > more evident, and it might well also speed up the to-idle and from-idle
> > fastpaths on some architectures.
> 
> Cleaning up the memory ordering requirements certainly seems worthwhile.
> But is there any straightforward benchmark that might quantify the
> "might well also speed up" here? How much does weakening the memory
> ordering buy us, in practice?

None that I know of!

							Thanx, Paul