From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Josh Triplett <josh@joshtriplett.org>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] Fix: disable sys_membarrier when nohz_full is enabled
Date: Thu, 17 Nov 2016 08:02:11 -0800 [thread overview]
Message-ID: <20161117160211.GB3612@linux.vnet.ibm.com> (raw)
In-Reply-To: <20161117101725.3abcb413@gandalf.local.home>
On Thu, Nov 17, 2016 at 10:17:25AM -0500, Steven Rostedt wrote:
> On Thu, 17 Nov 2016 15:02:18 +0000 (UTC)
> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
>
>
> > That's an interesting approach. I would be tempted to give it a
> > per-thread (rather than per-process) scope.
>
> Sure, per thread, but have it inherit to child processes.
>
> >
> > E.g., a thread could do the following to ask to be
> > interrupted by IPIs:
> >
> > membarrier(MEMBARRIER_CMD_REGISTER_EXPEDITED, 0)
> >
> > and could unregister with:
> >
> > membarrier(MEMBARRIER_CMD_UNREGISTER_EXPEDITED, 0)
>
> Sure why not ;-)
Makes a lot of sense to me!
> > We can then keep a per-thread refcount internally.
> > (not sure the "EXPEDITED" is the right word there...
> > do we want it to be "NOHZ_FULL" instead ?)
>
> No, it shouldn't mention NOHZ_FULL. Perhaps have all tasks do this
> regardless, even though it will only affect nohz full ones. But in the
> future it may be other tasks as well.
>
> >
> > Then in membarrier(MEMBARRIER_CMD_SHARED, 0), for each
> > nohz_full cpu, we grab the rq lock, and only send an IPI
> > if the running thread is registered as "expedited".
>
> Yeah, something like that. That way it wont interrupt tasks that are
> running in no-hz-full and don't care about this syscall.
And this as well!
Thanx, Paul
next prev parent reply other threads:[~2016-11-17 18:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-03 16:29 [PATCH] Fix: disable sys_membarrier when nohz_full is enabled Mathieu Desnoyers
2016-11-03 17:49 ` Paul E. McKenney
2016-11-07 17:08 ` Mathieu Desnoyers
2016-11-07 18:06 ` Paul E. McKenney
2016-11-07 18:10 ` Mathieu Desnoyers
2016-11-07 20:03 ` Paul E. McKenney
2016-11-08 11:15 ` Mathieu Desnoyers
2016-11-12 17:58 ` Paul E. McKenney
2016-11-17 6:51 ` Lai Jiangshan
2016-11-17 11:46 ` Mathieu Desnoyers
2016-11-17 13:40 ` Paul E. McKenney
2016-11-17 13:54 ` Mathieu Desnoyers
2016-11-17 14:09 ` Paul E. McKenney
2016-11-17 14:50 ` Steven Rostedt
2016-11-17 15:02 ` Mathieu Desnoyers
2016-11-17 15:17 ` Steven Rostedt
2016-11-17 16:02 ` Paul E. McKenney [this message]
2016-11-17 13:38 ` Paul E. McKenney
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