linux-kernel - Re: [PATCH v4 -rcu 3/4] rcu/segcblist: Add counters to segcblist datastructure

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Message-ID: <20200826142438.GO2855@paulmck-ThinkPad-P72>
Date:   Wed, 26 Aug 2020 07:24:39 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org, boqun.feng@...il.com,
        dave@...olabs.net, Ingo Molnar <mingo@...hat.com>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        neeraj.iitr10@...il.com, rcu@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>, vineethrp@...il.com
Subject: Re: [PATCH v4 -rcu 3/4] rcu/segcblist: Add counters to segcblist
 datastructure

On Tue, Aug 25, 2020 at 06:51:03PM -0400, Joel Fernandes wrote:
> On Tue, Aug 25, 2020 at 02:53:38PM -0700, Paul E. McKenney wrote:
> > On Mon, Aug 24, 2020 at 10:48:41PM -0400, Joel Fernandes (Google) wrote:
> > > Add counting of segment lengths of segmented callback list.
> > > 
> > > This will be useful for a number of things such as knowing how big the
> > > ready-to-execute segment have gotten. The immediate benefit is ability
> > > to trace how the callbacks in the segmented callback list change.
> > > 
> > > Tested by profusely reading traces when segcblist counts updated.
> > 
> > Might I recommend a more repeatable and sustainable test methodology?
> > (Sorry, couldn't resist, given that you left yourself wide open for
> > that one...)
> 
> Ah, this message was from an older series :-(. I did test it with rcutorture
> for many hours. But I forgot to update this commit message. :-(

That is better.  Let me see if I can find a more targeted test from the
old days...

> I will respond to other comments soon, I am still stuck on the comment about
> rcl.len and rcu_barrier interaction that you brought up in 1/4 and 2/4.

Hoping my more recent replies help.  If not, you know where to find me.

							Thanx, Paul