From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com,
ldr709@gmail.com
Subject: Re: [PATCH RFC tip/core/rcu] SRCU rewrite
Date: Tue, 15 Nov 2016 08:51:13 +0100 [thread overview]
Message-ID: <20161115075113.GN3142@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20161114183636.GA28589@linux.vnet.ibm.com>
On Mon, Nov 14, 2016 at 10:36:36AM -0800, Paul E. McKenney wrote:
> SRCU uses two per-cpu counters: a nesting counter to count the number of
> active critical sections, and a sequence counter to ensure that the nesting
> counters don't change while they are being added together in
> srcu_readers_active_idx_check().
>
> This patch instead uses per-cpu lock and unlock counters. Because the both
> counters only increase and srcu_readers_active_idx_check() reads the unlock
> counter before the lock counter, this achieves the same end without having
> to increment two different counters in srcu_read_lock(). This also saves a
> smp_mb() in srcu_readers_active_idx_check().
A very small improvement... I feel SRCU has much bigger issues :/
next prev parent reply other threads:[~2016-11-15 7:51 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-14 18:36 [PATCH RFC tip/core/rcu] SRCU rewrite Paul E. McKenney
2016-11-14 19:00 ` Mathieu Desnoyers
2016-11-15 1:44 ` Boqun Feng
2016-11-15 14:37 ` Paul E. McKenney
2016-11-17 12:18 ` Lai Jiangshan
2016-11-17 13:49 ` Paul E. McKenney
2016-11-17 14:38 ` Paul E. McKenney
2016-11-17 14:45 ` Boqun Feng
2016-11-17 15:54 ` Paul E. McKenney
2016-11-17 15:55 ` Lai Jiangshan
2016-11-17 17:42 ` Paul E. McKenney
2016-11-17 14:31 ` Boqun Feng
2016-11-17 15:03 ` Paul E. McKenney
2016-11-17 15:07 ` Lai Jiangshan
2016-11-17 15:31 ` Mathieu Desnoyers
2016-11-17 15:38 ` Mathieu Desnoyers
2016-11-17 15:53 ` Paul E. McKenney
2016-11-17 16:33 ` Mathieu Desnoyers
2016-11-17 20:31 ` Lance Roy
2016-11-15 7:51 ` Peter Zijlstra [this message]
2016-11-15 13:54 ` Mathieu Desnoyers
2016-11-15 13:59 ` Peter Zijlstra
2016-11-15 14:26 ` Paul E. McKenney
2016-11-15 14:55 ` Peter Zijlstra
2016-11-15 15:43 ` Paul E. McKenney
2016-11-17 13:58 ` Lai Jiangshan
2016-11-17 19:53 ` Lance Roy
2016-11-18 13:27 ` Paul E. McKenney
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