From: "Paul E. McKenney" <paulmck@linux.ibm.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
Josh Triplett <josh@joshtriplett.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
tglx@linutronix.de, Mike Galbraith <efault@gmx.de>
Subject: Re: [PATCH v2] rcu: Allow to eliminate softirq processing from rcutree
Date: Wed, 20 Mar 2019 08:44:40 -0700 [thread overview]
Message-ID: <20190320154440.GA16332@linux.ibm.com> (raw)
In-Reply-To: <20190320152146.GH4102@linux.ibm.com>
On Wed, Mar 20, 2019 at 08:21:46AM -0700, Paul E. McKenney wrote:
> On Wed, Mar 20, 2019 at 12:32:19PM +0100, Sebastian Andrzej Siewior wrote:
> > On 2019-03-19 12:44:19 [+0100], To Paul E. McKenney wrote:
> > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > > index 0f31b79eb6761..0a719f726e149 100644
> > > --- a/kernel/rcu/tree.c
> > > +++ b/kernel/rcu/tree.c
> > …
> > > +/*
> > > + * Spawn per-CPU RCU core processing kthreads.
> > > + */
> > > +static int __init rcu_spawn_core_kthreads(void)
> > > +{
> > > + int cpu;
> > > +
> > > + for_each_possible_cpu(cpu)
> > > + per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
> > > + if (!IS_ENABLED(CONFIG_RCU_BOOST) && !rcu_softirq_enabled)
> >
> > and this needs to become
> > - if (!IS_ENABLED(CONFIG_RCU_BOOST) && !rcu_softirq_enabled)
> > + if (!IS_ENABLED(CONFIG_RCU_BOOST) && rcu_softirq_enabled)
> >
> > With this change and hunk that I just sent to Joel I get thee three RCU
> > modes with and without BOOST booted.
> >
> > Unless there is something (and Paul agrees that the Joel hunk is
> > correct) I would post a v3 with those changes included.
>
> Well, I did get a bunch of grace-period hangs of various sorts when I
> ran rcutorture like this:
>
> tools/testing/selftests/rcutorture/bin/kvm.sh --memory 1G --bootargs rcunosoftirq
>
> I also got a silent hard hang on TREE03. And an rcutorture forward-progress
> failure, which goes along with the grace-period hangs.
>
> So something does need adjustment. I will try again with this change.
And it does seem to work better. I will give it more intense testing
later on, but in the meantime I have merged this change into your
earlier patch.
We will see whether or not I am able summon up the courage to push it
into v5.2, however. ;-)
Thanx, Paul
> > > + return 0;
> > > + WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), "%s: Could not start rcub kthread, OOM is now expected behavior\n", __func__);
> > > + return 0;
> > > +}
> > > +early_initcall(rcu_spawn_core_kthreads);
> >
> > Sebastian
> >
next prev parent reply other threads:[~2019-03-20 15:43 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-15 11:11 [PATCH] rcu: Allow to eliminate softirq processing from rcutree Sebastian Andrzej Siewior
2019-03-15 13:35 ` Steven Rostedt
2019-03-15 13:57 ` Sebastian Andrzej Siewior
2019-03-18 2:24 ` Paul E. McKenney
2019-03-19 11:44 ` [PATCH v2] " Sebastian Andrzej Siewior
2019-03-19 15:59 ` Paul E. McKenney
2019-03-19 16:24 ` Sebastian Andrzej Siewior
2019-03-19 16:50 ` Paul E. McKenney
2019-03-19 17:02 ` Sebastian Andrzej Siewior
2019-03-20 11:32 ` Sebastian Andrzej Siewior
2019-03-20 15:21 ` Paul E. McKenney
2019-03-20 15:44 ` Paul E. McKenney [this message]
2019-03-20 16:05 ` Sebastian Andrzej Siewior
2019-03-20 16:15 ` Paul E. McKenney
2019-03-20 16:35 ` Sebastian Andrzej Siewior
2019-03-20 17:30 ` Paul E. McKenney
2019-03-20 17:59 ` Sebastian Andrzej Siewior
2019-03-20 18:12 ` Paul E. McKenney
2019-03-20 18:14 ` Sebastian Andrzej Siewior
2019-03-20 21:13 ` [PATCH v3] " Sebastian Andrzej Siewior
2019-03-20 23:46 ` Paul E. McKenney
2019-03-21 8:27 ` Sebastian Andrzej Siewior
2019-03-21 13:26 ` Paul E. McKenney
2019-03-21 23:32 ` Paul E. McKenney
2019-03-22 7:35 ` Paul E. McKenney
2019-03-22 12:43 ` Paul E. McKenney
2019-03-22 13:42 ` Joel Fernandes
2019-03-22 14:58 ` Paul E. McKenney
2019-03-22 15:50 ` Joel Fernandes
2019-03-22 16:26 ` Paul E. McKenney
2019-03-22 18:07 ` Paul E. McKenney
2019-03-22 23:48 ` Joel Fernandes
2019-03-23 0:25 ` Paul E. McKenney
2019-03-23 1:04 ` Joel Fernandes
2019-03-23 16:10 ` Paul E. McKenney
2019-03-24 23:42 ` Paul E. McKenney
2019-03-25 13:41 ` Joel Fernandes
2019-03-25 15:08 ` Paul E. McKenney
2019-03-25 15:52 ` Paul E. McKenney
2019-03-20 0:26 ` [PATCH] " Joel Fernandes
2019-03-20 11:28 ` Sebastian Andrzej Siewior
2019-03-21 12:06 ` Joel Fernandes
2019-03-21 13:52 ` Paul E. McKenney
2019-03-20 15:24 ` Paul E. McKenney
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