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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	dipankar <dipankar@in.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Josh Triplett <josh@joshtriplett.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	rostedt <rostedt@goodmis.org>,
	David Howells <dhowells@redhat.com>,
	Eric Dumazet <edumazet@google.com>,
	dvhart <dvhart@linux.intel.com>, fweisbec <fweisbec@gmail.com>,
	Oleg Nesterov <oleg@redhat.com>,
	bobby prani <bobby.prani@gmail.com>, ldr709 <ldr709@gmail.com>
Subject: Re: [PATCH RFC tip/core/rcu] SRCU rewrite
Date: Tue, 15 Nov 2016 13:54:50 +0000 (UTC)	[thread overview]
Message-ID: <1857730044.1901.1479218090893.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20161115075113.GN3142@twins.programming.kicks-ass.net>

----- On Nov 15, 2016, at 2:51 AM, Peter Zijlstra peterz@infradead.org wrote:

> 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 :/

Do you have specific issues in mind ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

  reply	other threads:[~2016-11-15 13:54 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
2016-11-15 13:54   ` Mathieu Desnoyers [this message]
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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