Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 23 Jun 2020 17:01:11 -0400
From:   Joel Fernandes <joel@joelfernandes.org>
To:     "Paul E. McKenney" <paulmck@kernel.org>
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com,
        dipankar@in.ibm.com, akpm@linux-foundation.org,
        mathieu.desnoyers@efficios.com, josh@joshtriplett.org,
        tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org,
        dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com,
        oleg@redhat.com, linux-mm@kvack.org
Subject: Re: [PATCH tip/core/rcu 02/26] mm/mmap.c: Add cond_resched() for
 exit_mmap() CPU stalls
Message-ID: <20200623210111.GA117936@google.com>
References: <20200623002128.GA25456@paulmck-ThinkPad-P72>
 <20200623002147.25750-2-paulmck@kernel.org>
 <20200623193431.GA68372@google.com>
 <20200623205508.GS9247@paulmck-ThinkPad-P72>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200623205508.GS9247@paulmck-ThinkPad-P72>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jun 23, 2020 at 01:55:08PM -0700, Paul E. McKenney wrote:
[..] 
> > Just for my understanding, cond_resched_tasks_rcu_qs() may not help here
> > because preemption is not disabled right? Still I see no harm in using it
> > here either as it may give a slight speed up for tasks-RCU.
> 
> The RCU-tasks stall-warning interval is ten minutes, and I have not yet
> seen evidence that we are getting close to that.  If we do, then yes,
> a cond_resched_tasks_rcu_qs() might be in this code's future.  But it
> does add overhead, so we need to see the evidence first.

Yes, true about that overhead. Ok, this is fine with me too, thanks :)

 - Joel