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Re: [PATCH RFC tip/core/rcu] SRCU rewrite

From Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Newsgroups linux.kernel
Subject Re: [PATCH RFC tip/core/rcu] SRCU rewrite
Date 2016-11-15 15:00 +0100
Message-ID <sDMrf-5C7-11@gated-at.bofh.it> (permalink)
References <sDukH-2cH-83@gated-at.bofh.it> <sDGOS-22f-25@gated-at.bofh.it>
Organization linux.* mail to news gateway

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----- 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

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Thread

[PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-14 19:40 +0100
  Re: [PATCH RFC tip/core/rcu] SRCU rewrite Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-11-14 20:10 +0100
  Re: [PATCH RFC tip/core/rcu] SRCU rewrite Boqun Feng <boqun.feng@gmail.com> - 2016-11-15 02:50 +0100
    Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-15 15:40 +0100
      Re: [PATCH RFC tip/core/rcu] SRCU rewrite Boqun Feng <boqun.feng@gmail.com> - 2016-11-17 15:40 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-11-17 18:10 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-17 18:20 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite Lai Jiangshan <jiangshanlai@gmail.com> - 2016-11-17 18:30 +0100
          Re: [PATCH RFC tip/core/rcu] SRCU rewrite Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-11-17 19:00 +0100
            Re: [PATCH RFC tip/core/rcu] SRCU rewrite Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-11-17 19:10 +0100
              Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-17 22:30 +0100
          Re: [PATCH RFC tip/core/rcu] SRCU rewrite Lance Roy <ldr709@gmail.com> - 2016-11-17 21:40 +0100
      Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-17 18:20 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-17 18:50 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite Lai Jiangshan <jiangshanlai@gmail.com> - 2016-11-17 19:20 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite Boqun Feng <boqun.feng@gmail.com> - 2016-11-17 19:40 +0100
          Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-17 20:20 +0100
      Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-17 19:50 +0100
      Re: [PATCH RFC tip/core/rcu] SRCU rewrite Lai Jiangshan <jiangshanlai@gmail.com> - 2016-11-17 19:50 +0100
  Re: [PATCH RFC tip/core/rcu] SRCU rewrite Peter Zijlstra <peterz@infradead.org> - 2016-11-15 09:00 +0100
    Re: [PATCH RFC tip/core/rcu] SRCU rewrite Peter Zijlstra <peterz@infradead.org> - 2016-11-15 15:00 +0100
      Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-15 15:30 +0100
        Re: [PATCH RFC tip/core/rcu] SRCU rewrite Peter Zijlstra <peterz@infradead.org> - 2016-11-15 16:00 +0100
          Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-15 16:50 +0100
    Re: [PATCH RFC tip/core/rcu] SRCU rewrite Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2016-11-15 15:00 +0100
  Re: [PATCH RFC tip/core/rcu] SRCU rewrite Lai Jiangshan <jiangshanlai@gmail.com> - 2016-11-17 19:00 +0100
    Re: [PATCH RFC tip/core/rcu] SRCU rewrite Lance Roy <ldr709@gmail.com> - 2016-11-17 21:00 +0100
      Re: [PATCH RFC tip/core/rcu] SRCU rewrite "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-11-18 14:40 +0100

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