From: Byungchul Park <byungchul.park@lge.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>,
josh@joshtriplett.org, rostedt@goodmis.org,
mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com,
rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@lge.com
Subject: Re: [PATCH] rcu: Make jiffies_till_sched_qs writable
Date: Tue, 9 Jul 2019 15:45:31 +0900 [thread overview]
Message-ID: <20190709064531.GA15734@X58A-UD3R> (raw)
In-Reply-To: <20190709055815.GA19459@X58A-UD3R>
On Tue, Jul 09, 2019 at 02:58:16PM +0900, Byungchul Park wrote:
> On Mon, Jul 08, 2019 at 09:03:59AM -0400, Joel Fernandes wrote:
> > > Actually, the intent was to only allow this to be changed at boot time.
> > > Of course, if there is now a good reason to adjust it, it needs
> > > to be adjustable. So what situation is making you want to change
> > > jiffies_till_sched_qs at runtime? To what values is it proving useful
> > > to adjust it? What (if any) relationships between this timeout and the
> > > various other RCU timeouts need to be maintained? What changes to
> > > rcutorture should be applied in order to test the ability to change
> > > this at runtime?
> >
> > I am also interested in the context, are you changing it at runtime for
> > experimentation? I recently was doing some performance experiments and it is
> > quite interesting how reducing this value can shorten grace period times :)
>
> Hi Joel,
>
> I've read a thread talking about your experiment to see how the grace
> periods change depending on the tunnable variables which was interesting
> to me. While reading it, I found out jiffies_till_sched_qs is not
> tunnable at runtime unlike jiffies_till_{first,next}_fqs which looks
> like non-sense to me that's why I tried this patch. :)
>
> Hi Paul,
>
> IMHO, as much as we want to tune the time for fqs to be initiated, we
> can also want to tune the time for the help from scheduler to start.
Let me mention one more thing here...
This is about jiffies_till_sched_qs, I think, used to directly set
jiffies_to_sched_qs.
> I thought only difference between them is a level of urgency.
Of course, they are coupled in case jiffies_to_sched_qs is calculated
from jiffies_till_{first,next}_fqs though, I'm just talking about its
original motivation or concept.
Thanks,
Byungchul
next prev parent reply other threads:[~2019-07-09 6:46 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 6:00 [PATCH] rcu: Make jiffies_till_sched_qs writable Byungchul Park
2019-07-08 12:50 ` Paul E. McKenney
2019-07-08 13:03 ` Joel Fernandes
2019-07-08 13:19 ` Paul E. McKenney
2019-07-08 14:15 ` Joel Fernandes
2019-07-09 6:05 ` Byungchul Park
2019-07-09 12:43 ` Paul E. McKenney
2019-07-09 5:58 ` Byungchul Park
2019-07-09 6:45 ` Byungchul Park [this message]
2019-07-09 12:41 ` Paul E. McKenney
2019-07-10 1:20 ` Byungchul Park
2019-07-11 12:30 ` Paul E. McKenney
2019-07-11 13:08 ` Joel Fernandes
2019-07-11 15:02 ` Paul E. McKenney
2019-07-11 16:48 ` Joel Fernandes
2019-07-11 19:58 ` Joel Fernandes
2019-07-12 6:32 ` Byungchul Park
2019-07-12 12:51 ` Joel Fernandes
2019-07-12 13:02 ` Paul E. McKenney
2019-07-12 13:43 ` Joel Fernandes
2019-07-12 14:53 ` Paul E. McKenney
2019-07-13 8:47 ` Byungchul Park
2019-07-13 14:20 ` Joel Fernandes
2019-07-13 15:13 ` Paul E. McKenney
2019-07-13 15:42 ` Joel Fernandes
2019-07-13 17:41 ` Paul E. McKenney
2019-07-14 13:39 ` Byungchul Park
2019-07-14 13:56 ` Paul E. McKenney
2019-07-15 17:39 ` Joel Fernandes
2019-07-15 20:09 ` Paul E. McKenney
2019-07-18 16:14 ` Joel Fernandes
2019-07-18 16:15 ` Joel Fernandes
2019-07-18 21:34 ` Paul E. McKenney
2019-07-19 0:48 ` Joel Fernandes
2019-07-19 0:54 ` Byungchul Park
2019-07-19 0:39 ` Byungchul Park
2019-07-19 0:52 ` Joel Fernandes
2019-07-19 1:10 ` Byungchul Park
2019-07-19 7:43 ` Paul E. McKenney
2019-07-19 9:57 ` Byungchul Park
2019-07-19 19:57 ` Paul E. McKenney
2019-07-19 20:33 ` Joel Fernandes
2019-07-23 11:05 ` Byungchul Park
2019-07-23 13:47 ` Paul E. McKenney
2019-07-23 16:54 ` Paul E. McKenney
2019-07-24 7:58 ` Byungchul Park
2019-07-24 7:59 ` Byungchul Park
2019-07-12 13:01 ` Paul E. McKenney
2019-07-12 13:40 ` Joel Fernandes
2019-07-12 6:00 ` Byungchul Park
2019-07-12 5:52 ` Byungchul Park
2019-07-12 5:48 ` Byungchul Park
2019-07-13 9:08 ` Byungchul Park
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