From: Byungchul Park <byungchul.park@lge.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>,
Byungchul Park <max.byungchul.park@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Rao Shoaib <rao.shoaib@oracle.com>,
kernel-team@android.com, kernel-team <kernel-team@lge.com>,
Davidlohr Bueso <dave@stgolabs.net>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
rcu <rcu@vger.kernel.org>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree_rcu batching
Date: Tue, 13 Aug 2019 14:29:54 +0900 [thread overview]
Message-ID: <20190813052954.GA18373@X58A-UD3R> (raw)
In-Reply-To: <20190812131234.GC27552@google.com>
On Mon, Aug 12, 2019 at 09:12:34AM -0400, Joel Fernandes wrote:
> On Mon, Aug 12, 2019 at 07:10:52PM +0900, Byungchul Park wrote:
> > On Sun, Aug 11, 2019 at 04:49:39PM -0700, Paul E. McKenney wrote:
> > > Maybe. Note well that I said "potential issue". When I checked a few
> > > years ago, none of the uses of rcu_barrier() cared about kfree_rcu().
> > > They cared instead about call_rcu() callbacks that accessed code or data
> > > that was going to disappear soon, for example, due to module unload or
> > > filesystem unmount.
> > >
> > > So it -might- be that rcu_barrier() can stay as it is, but with changes
> > > as needed to documentation.
>
> Right, we should update the docs. Byungchul, do you mind sending a patch that
> documents the rcu_barrier() behavior?
Are you trying to give me the chance? I feel thankful. It doens't matter
to try it at the moment though, I can't follow-up until September. I'd
better do that in Septamber or give it up this time.
Thanks,
Byungchul
> > > It also -might- be, maybe now or maybe some time in the future, that
> > > there will need to be a kfree_rcu_barrier() or some such. But if so,
> > > let's not create it until it is needed. For one thing, it is reasonably
> > > likely that something other than a kfree_rcu_barrier() would really
> > > be what was needed. After all, the main point would be to make sure
> > > that the old memory really was freed before allocating new memory.
> >
> > Now I fully understand what you meant thanks to you. Thank you for
> > explaining it in detail.
> >
> > > But if the system had ample memory, why wait? In that case you don't
> > > really need to wait for all the old memory to be freed, but rather for
> > > sufficient memory to be available for allocation.
> >
> > Agree. Totally make sense.
>
> Agreed, all makes sense.
>
> thanks,
>
> - Joel
>
> [snip]
next prev parent reply other threads:[~2019-08-13 5:31 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 21:20 [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree_rcu batching Joel Fernandes (Google)
2019-08-06 21:20 ` [PATCH RFC v1 2/2] rcuperf: Add kfree_rcu performance Tests Joel Fernandes (Google)
2019-08-07 0:29 ` Paul E. McKenney
2019-08-07 10:22 ` Joel Fernandes
2019-08-07 17:56 ` Paul E. McKenney
2019-08-09 16:01 ` Joel Fernandes
2019-08-11 2:01 ` Joel Fernandes
2019-08-11 23:42 ` Paul E. McKenney
2019-08-06 23:56 ` [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree_rcu batching Paul E. McKenney
2019-08-07 9:45 ` Joel Fernandes
2019-08-07 17:52 ` Paul E. McKenney
2019-08-08 9:52 ` Byungchul Park
2019-08-08 12:56 ` Joel Fernandes
2019-08-08 14:23 ` Byungchul Park
2019-08-08 18:09 ` Paul E. McKenney
2019-08-11 8:36 ` Byungchul Park
2019-08-11 8:49 ` Byungchul Park
2019-08-11 23:49 ` Paul E. McKenney
2019-08-12 10:10 ` Byungchul Park
2019-08-12 13:12 ` Joel Fernandes
2019-08-13 5:29 ` Byungchul Park [this message]
2019-08-13 15:41 ` Paul E. McKenney
2019-08-14 0:11 ` Byungchul Park
2019-08-14 2:53 ` Paul E. McKenney
2019-08-14 3:43 ` Byungchul Park
2019-08-14 16:59 ` Paul E. McKenney
2019-08-11 10:37 ` Byungchul Park
2019-08-08 23:30 ` Joel Fernandes
2019-08-09 15:16 ` Paul E. McKenney
2019-08-09 15:39 ` Joel Fernandes
2019-08-09 16:33 ` Paul E. McKenney
2019-08-09 20:22 ` Joel Fernandes
2019-08-09 20:26 ` Joel Fernandes
2019-08-09 21:25 ` Joel Fernandes
2019-08-10 3:38 ` Paul E. McKenney
2019-08-09 20:29 ` Joel Fernandes
2019-08-09 20:42 ` Paul E. McKenney
2019-08-09 21:36 ` Joel Fernandes
2019-08-10 3:40 ` Paul E. McKenney
2019-08-10 3:52 ` Joel Fernandes
2019-08-10 2:42 ` Joel Fernandes
2019-08-10 3:38 ` Paul E. McKenney
2019-08-10 4:20 ` Joel Fernandes
2019-08-10 18:24 ` Paul E. McKenney
2019-08-11 2:26 ` Joel Fernandes
2019-08-11 23:35 ` Paul E. McKenney
2019-08-12 13:13 ` Joel Fernandes
2019-08-12 14:44 ` Paul E. McKenney
2019-08-08 10:26 ` Byungchul Park
2019-08-08 18:11 ` Paul E. McKenney
2019-08-08 20:13 ` Joel Fernandes
2019-08-08 20:51 ` Paul E. McKenney
2019-08-08 22:34 ` Joel Fernandes
2019-08-08 22:37 ` Paul E. McKenney
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