From: "Paul E. McKenney" <paulmck@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Joel Fernandes <joel@joelfernandes.org>,
Josh Triplett <josh@joshtriplett.org>
Subject: Re: [RFC PATCH 11/12] rcu: Locally accelerate callbacks as long as offloading isn't complete
Date: Mon, 21 Sep 2020 17:24:52 -0700 [thread overview]
Message-ID: <20200922002452.GR29330@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200921124351.24035-12-frederic@kernel.org>
On Mon, Sep 21, 2020 at 02:43:50PM +0200, Frederic Weisbecker wrote:
> I have no idea what I'm doing but doing that looks necessary to me.
Now -there- is a commit log that inspires confidence!!! ;-)
> Inspired-by: Paul E. McKenney <paulmck@kernel.org>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> Cc: Paul E. McKenney <paulmck@kernel.org>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
> Cc: Joel Fernandes <joel@joelfernandes.org>
> ---
> kernel/rcu/tree.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 928907e9ba94..8cef5ea8d1f0 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2619,7 +2619,6 @@ static __latent_entropy void rcu_core(void)
> unsigned long flags;
> struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
> struct rcu_node *rnp = rdp->mynode;
> - const bool offloaded = rcu_segcblist_is_offloaded(&rdp->cblist);
> const bool do_batch = !rcu_segcblist_completely_offloaded(&rdp->cblist);
>
> if (cpu_is_offline(smp_processor_id()))
> @@ -2640,11 +2639,11 @@ static __latent_entropy void rcu_core(void)
>
> /* No grace period and unregistered callbacks? */
> if (!rcu_gp_in_progress() &&
> - rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) {
> - local_irq_save(flags);
> + rcu_segcblist_is_enabled(&rdp->cblist) && do_batch) {
> + rcu_nocb_lock_irqsave(rdp, flags);
> if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
> rcu_accelerate_cbs_unlocked(rnp, rdp);
It might also be that rcu_advance_cbs() is needed somewhere. I will
need to look carefully to work out whether either of them need to be
invoked at this particular point in the code.
Thanx, Paul
> - local_irq_restore(flags);
> + rcu_nocb_unlock_irqrestore(rdp, flags);
> }
>
> rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());
> --
> 2.28.0
>
next prev parent reply other threads:[~2020-09-22 0:24 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 12:43 [RFC PATCH 00/12] rcu/nocb: De-offload and re-offload support v2 Frederic Weisbecker
2020-09-21 12:43 ` [RFC PATCH 01/12] rcu: Implement rcu_segcblist_is_offloaded() config dependent Frederic Weisbecker
2020-09-22 0:27 ` Paul E. McKenney
2020-09-22 21:43 ` Frederic Weisbecker
2020-09-22 23:11 ` Paul E. McKenney
2020-09-23 15:25 ` Frederic Weisbecker
2020-09-21 12:43 ` [RFC PATCH 02/12] rcu: Turn enabled/offload states into a common flag Frederic Weisbecker
2020-09-21 12:43 ` [RFC PATCH 03/12] rcu: Provide basic callback offloading state machine bits Frederic Weisbecker
2020-09-21 23:50 ` Paul E. McKenney
2020-09-21 12:43 ` [RFC PATCH 04/12] rcu: De-offloading CB kthread Frederic Weisbecker
2020-09-22 0:07 ` Paul E. McKenney
2020-09-21 12:43 ` [RFC PATCH 05/12] rcu: De-offloading GP kthread Frederic Weisbecker
2020-09-22 0:10 ` Paul E. McKenney
2020-09-23 15:31 ` Frederic Weisbecker
2020-09-23 15:48 ` Paul E. McKenney
2020-09-21 12:43 ` [RFC PATCH 06/12] rcu: Re-offload support Frederic Weisbecker
2020-09-21 12:43 ` [RFC PATCH 07/12] rcu: Shutdown nocb timer on de-offloading Frederic Weisbecker
2020-09-22 0:17 ` Paul E. McKenney
2020-09-23 15:29 ` Frederic Weisbecker
2020-09-23 15:47 ` Paul E. McKenney
2020-09-21 12:43 ` [RFC PATCH 08/12] rcu: Flush bypass before setting SEGCBLIST_SOFTIRQ_ONLY Frederic Weisbecker
2020-09-21 12:43 ` [RFC PATCH 09/12] rcu: Set SEGCBLIST_SOFTIRQ_ONLY at the very last stage of de-offloading Frederic Weisbecker
2020-09-21 12:43 ` [RFC PATCH 10/12] rcu: Process batch locally as long as offloading isn't complete Frederic Weisbecker
2020-09-22 0:22 ` Paul E. McKenney
2020-09-21 12:43 ` [RFC PATCH 11/12] rcu: Locally accelerate callbacks " Frederic Weisbecker
2020-09-22 0:24 ` Paul E. McKenney [this message]
2020-09-21 12:43 ` [RFC PATCH 12/12] rcu: Nocb (de)activate through sysfs Frederic Weisbecker
2020-09-22 0:26 ` Paul E. McKenney
2020-09-23 15:27 ` Frederic Weisbecker
2020-09-23 15:47 ` Paul E. McKenney
2020-09-23 19:00 ` Frederic Weisbecker
2020-09-24 0:38 ` Paul E. McKenney
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200922002452.GR29330@paulmck-ThinkPad-P72 \
--to=paulmck@kernel.org \
--cc=frederic@kernel.org \
--cc=jiangshanlai@gmail.com \
--cc=joel@joelfernandes.org \
--cc=josh@joshtriplett.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mathieu.desnoyers@efficios.com \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).