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Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob

From Oleg Nesterov <oleg@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob
Date 2016-07-14 20:50 +0200
Message-ID <rUTRU-4Q7-35@gated-at.bofh.it> (permalink)
References <rUTIe-4Mw-13@gated-at.bofh.it> <rUTIe-4Mw-17@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On 07/14, Peter Zijlstra wrote:
>
> The current percpu-rwsem read side is entirely free of serializing
> instructions at the cost of having a synchronize_sched() in the write
> path.
>
> The latency of the synchronize_sched() is too high for some users
> (cgroups), so provide a __percpu_init_rwsem(.bias) argument to forgot
> this synchronize_sched() at the cost of forcing all readers into the
> slow path, which has serializing instructions.

Oh well... I personally do not think this is what we want... Can't
we just add the stupid rcu_sync_enter() into cgroup_init() at least
for now? Yes, this means the unnecessary .sync() at boot time, but
it will go away after cleanups I am going to send.

Because, again, we will probably want to change this bias dynamically.

Oleg.

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Thread

[PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Peter Zijlstra <peterz@infradead.org> - 2016-07-14 20:40 +0200
  Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Oleg Nesterov <oleg@redhat.com> - 2016-07-14 20:50 +0200
    Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Peter Zijlstra <peterz@infradead.org> - 2016-07-14 21:00 +0200
    Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Peter Zijlstra <peterz@infradead.org> - 2016-07-14 21:30 +0200
      Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-14 21:30 +0200
        Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Peter Zijlstra <peterz@infradead.org> - 2016-07-14 21:40 +0200
          Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-14 22:00 +0200
      Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Oleg Nesterov <oleg@redhat.com> - 2016-07-15 15:30 +0200
        Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-15 15:40 +0200
          Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Oleg Nesterov <oleg@redhat.com> - 2016-07-15 15:50 +0200
            Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-15 17:40 +0200
              Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Oleg Nesterov <oleg@redhat.com> - 2016-07-15 18:50 +0200
                Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-15 20:10 +0200
                [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-16 19:20 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-16 20:50 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Peter Zijlstra <peterz@infradead.org> - 2016-07-18 14:00 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-18 15:50 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-19 23:00 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-20 17:20 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-20 23:00 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-21 19:40 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-20 19:20 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-20 23:40 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-21 19:40 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-22 05:30 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce __rcu_sync_enter() John Stultz <john.stultz@linaro.org> - 2016-07-25 19:10 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-25 19:30 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() Oleg Nesterov <oleg@redhat.com> - 2016-07-25 19:10 +0200
                Re: [PATCH] rcu_sync: simplify the state machine, introduce  __rcu_sync_enter() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-07-25 19:50 +0200
      Re: [PATCH 2/2] locking/percpu-rwsem: Introduce bias knob Oleg Nesterov <oleg@redhat.com> - 2016-07-15 15:50 +0200

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