From: "Paul E. McKenney" <paulmck@kernel.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org, Davidlohr Bueso <dave@stgolabs.net>,
Ingo Molnar <mingo@redhat.com>,
Josh Triplett <josh@joshtriplett.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Marco Elver <elver@google.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
"Uladzislau Rezki (Sony)" <urezki@gmail.com>
Subject: Re: [PATCH 5/7] rcu/trace: Use rsp's gp_seq in acceleration's rcu_grace_period tracepoint
Date: Thu, 18 Jun 2020 15:27:21 -0700 [thread overview]
Message-ID: <20200618222721.GA2723@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200618202955.4024-5-joel@joelfernandes.org>
On Thu, Jun 18, 2020 at 04:29:53PM -0400, Joel Fernandes (Google) wrote:
> During acceleration of CB, the rsp's gp_seq is rcu_seq_snap'd. This is
> the value used for acceleration - it is the value of gp_seq at which it
> is safe the execute all callbacks in the callback list.
>
> The rdp's gp_seq is not very useful for this scenario. Make
> rcu_grace_period report the rsp's gp_seq instead as it allows one to
> reason about how the acceleration works.
Good catch, but please instead trace the gp_seq_req local variable.
Thanx, Paul
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
> kernel/rcu/tree.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 81df1b837dd9d..c3bae7a83d792 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1437,9 +1437,9 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
>
> /* Trace depending on how much we were able to accelerate. */
> if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
> - trace_rcu_grace_period(rcu_state.name, "rdp", rdp->gp_seq, TPS("AccWaitCB"));
> + trace_rcu_grace_period(rcu_state.name, "rsp", rcu_state.gp_seq, TPS("AccWaitCB"));
> else
> - trace_rcu_grace_period(rcu_state.name, "rdp", rdp->gp_seq, TPS("AccReadyCB"));
> + trace_rcu_grace_period(rcu_state.name, "rsp", rcu_state.gp_seq, TPS("AccReadyCB"));
>
> /* Count CBs for tracing. */
> rcu_segcblist_countseq(&rdp->cblist, cbs, gps);
> --
> 2.27.0.111.gc72c7da667-goog
>
next prev parent reply other threads:[~2020-06-18 22:27 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 20:29 [PATCH 1/7] rcu/segcblist: Prevent useless GP start if no CBs to accelerate Joel Fernandes (Google)
2020-06-18 20:29 ` [PATCH 2/7] rcu/trace: Add tracing for how segcb list changes Joel Fernandes (Google)
2020-06-18 22:16 ` Paul E. McKenney
2020-06-18 23:52 ` Joel Fernandes
2020-06-18 20:29 ` [PATCH 3/7] rcu/trace: Add name of the source for gp_seq Joel Fernandes (Google)
2020-06-18 22:19 ` Paul E. McKenney
2020-06-18 23:51 ` Joel Fernandes
2020-06-19 0:12 ` Paul E. McKenney
2020-06-19 0:56 ` Joel Fernandes
2020-06-19 1:08 ` Joel Fernandes
2020-06-19 0:01 ` Steven Rostedt
2020-06-19 1:01 ` Joel Fernandes
2020-06-18 20:29 ` [PATCH 4/7] rcu/trace: Print negative GP numbers correctly Joel Fernandes (Google)
2020-06-18 22:30 ` Paul E. McKenney
2020-06-18 20:29 ` [PATCH 5/7] rcu/trace: Use rsp's gp_seq in acceleration's rcu_grace_period tracepoint Joel Fernandes (Google)
2020-06-18 22:27 ` Paul E. McKenney [this message]
2020-06-18 23:54 ` Joel Fernandes
2020-06-18 20:29 ` [PATCH 6/7] rcutorture: Add support to get the number of wakeups of main GP kthread Joel Fernandes (Google)
2020-06-18 22:40 ` Paul E. McKenney
2020-06-19 0:01 ` Joel Fernandes
2020-06-19 0:12 ` Paul E. McKenney
2020-06-19 1:00 ` Joel Fernandes
2020-06-19 3:23 ` Paul E. McKenney
2020-06-18 20:29 ` [PATCH 7/7] rcutorture: Add number of GP information to reports Joel Fernandes (Google)
2020-06-18 23:27 ` Paul E. McKenney
2020-06-18 22:11 ` [PATCH 1/7] rcu/segcblist: Prevent useless GP start if no CBs to accelerate Paul E. McKenney
2020-06-18 23:09 ` Paul E. McKenney
2020-06-19 0:04 ` Joel Fernandes
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