linux-kernel - Re: [PATCH v2] rcu: Allow to eliminate softirq processing from rcutree

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Date:   Tue, 19 Mar 2019 09:50:07 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, tglx@...utronix.de,
        Mike Galbraith <efault@....de>
Subject: Re: [PATCH v2] rcu: Allow to eliminate softirq processing from
 rcutree

On Tue, Mar 19, 2019 at 05:24:31PM +0100, Sebastian Andrzej Siewior wrote:
> On 2019-03-19 08:59:23 [-0700], Paul E. McKenney wrote:
> > I doubt that there is any code left from my original, so I set you as
> > author.  
> 
> I always forward ported it the patch over the years. So if it is no
> longer what it was once so be it. 

Besides, it looks very weird for me to have two Signed-off-by lines.  ;-)

> > I queued this and am starting tests without setting rcunosoftirq,
> > and will run more later setting it, courtesy of --bootargs.
> 
> oki.
> 
> > Steve Rostedt did raise a good question about adding event tracing to
> > the park functions.  I haven't really settled on an answer yet.  Thoughts?
> 
> It should trigger CPU hotplug events. If there was something similar for
> the softirq processing then the threaded processing should also have it.
> Please tell me which one should be added and I'm happy to add one.

In theory, the trace_rcu_utilization() should be added, just like at
the beginning and end of the function rcu_core(), but as far as I know,
no one uses that, so I actually have it on my list to remove.

							Thanx, Paul