Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

From	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option
Date	2017-07-26 17:50 +0200
Message-ID	<u7wJr-2ak-1@gated-at.bofh.it> (permalink)
References	(5 earlier) <u7eCV-7wj-77@gated-at.bofh.it> <u7fpf-86t-19@gated-at.bofh.it> <u7g1Z-8nQ-41@gated-at.bofh.it> <u7gOl-s4-9@gated-at.bofh.it> <u7peV-5RS-7@gated-at.bofh.it>
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On Wed, Jul 26, 2017 at 09:46:56AM +0200, Peter Zijlstra wrote:
> On Tue, Jul 25, 2017 at 10:50:13PM +0000, Mathieu Desnoyers wrote:
> > This would implement a MEMBARRIER_CMD_PRIVATE_EXPEDITED (or such) flag
> > for expedited process-local effect. This differs from the "SHARED" flag,
> > since the SHARED flag affects threads accessing memory mappings shared
> > across processes as well.
> > 
> > I wonder if we could create a MEMBARRIER_CMD_SHARED_EXPEDITED behavior
> > by iterating on all memory mappings mapped into the current process,
> > and build a cpumask based on the union of all mm masks encountered ?
> > Then we could send the IPI to all cpus belonging to that cpumask. Or
> > am I missing something obvious ?
> 
> I would readily object to such a beast. You far too quickly end up
> having to IPI everybody because of some stupid shared map or something
> (yes I know, normal DSOs are mapped private).

Agreed, we should keep things simple to start with.  The user can always
invoke sys_membarrier() from each process.

							Thanx, Paul

> The whole private_expedited is only palatable because we can only hinder
> our own threads (much).
>

Thread

[PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 00:00 +0200
  Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-25 06:30 +0200
    Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 18:30 +0200
  Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-25 15:20 +0200
    Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 18:50 +0200
  Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 18:40 +0200
    Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 18:50 +0200
      Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 19:10 +0200
        Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 19:20 +0200
          Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 21:00 +0200
            Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 21:40 +0200
              Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-25 22:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-25 23:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-26 00:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 00:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 00:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 02:10 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-26 09:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 17:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 20:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 20:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-26 22:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 23:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 03:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Mathieu Desnoyers <mathieu.desnoyers@efficios.com> - 2017-07-27 14:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 12:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 17:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 11:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 12:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Will Deacon <will.deacon@arm.com> - 2017-07-27 12:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 15:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 02:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-26 09:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 17:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 10:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 15:10 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 15:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 16:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 16:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 17:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-27 16:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-27 16:30 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Will Deacon <will.deacon@arm.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Boqun Feng <boqun.feng@gmail.com> - 2017-07-27 16:50 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 17:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Will Deacon <will.deacon@arm.com> - 2017-07-26 11:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-26 17:50 +0200
              Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 12:20 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 15:00 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option Peter Zijlstra <peterz@infradead.org> - 2017-07-27 15:40 +0200
                Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-07-27 16:40 +0200

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