From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: linux-kernel@vger.kernel.org, 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, joel.opensrc@gmail.com,
torvalds@linux-foundation.org, npiggin@gmail.com
Subject: Re: [tip/core/rcu, 05/21] rcu: Make rcu_gp_cleanup() more accurately predict need for new GP
Date: Fri, 11 May 2018 09:24:43 -0700 [thread overview]
Message-ID: <20180511162443.GA26088@linux.vnet.ibm.com> (raw)
In-Reply-To: <20180510173754.GB228531@joelaf.mtv.corp.google.com>
On Thu, May 10, 2018 at 10:37:54AM -0700, Joel Fernandes wrote:
> On Thu, May 10, 2018 at 06:15:46AM -0700, Paul E. McKenney wrote:
> [...]
> > > Also in rcu_future_gp_cleanup, we call:
> > > trace_rcu_future_gp(rnp, rdp, c,
> > > needmore ? TPS("CleanupMore") : TPS("Cleanup"));
> > > For this case, in the final trace event record, rnp->completed and c will be
> > > the same, since c is set to rnp->completed before calling
> > > trace_rcu_future_gp. I was thinking they should be different, do you expect
> > > them to be the same?
> >
> > Hmmm... That does look a bit inconsistent. And it currently uses
> > rnp->gp_seq instead of rnp->gp_seq_needed despite having the same
> > "CleanupMore" name.
> >
> > Looks like a review of the calls to trace_rcu_this_gp() is in order.
>
> I see you changed trace_rcu_future_gp to use trace_rcu_this_gp in 15/21.. I
> am not sure if the concern is still valid then since you seem to be correctly
> getting the future GP in those cases, except for the naming which I suggest
> be changed from 'c' to 'future_gp' just for clarity / self-documenting code.
Indeed, "c" for "->completed" is completely outdated. ;-)
Would you be willing to send a patch providing a better name?
Thanx, Paul
next prev parent reply other threads:[~2018-05-11 16:23 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-23 3:02 [PATCH tip/core/rcu 0/21] Contention reduction for v4.18 Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 01/21] rcu: Improve non-root rcu_cbs_completed() accuracy Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 02/21] rcu: Make rcu_start_future_gp()'s grace-period check more precise Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 03/21] rcu: Add accessor macros for the ->need_future_gp[] array Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 04/21] rcu: Make rcu_gp_kthread() check for early-boot activity Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 05/21] rcu: Make rcu_gp_cleanup() more accurately predict need for new GP Paul E. McKenney
2018-05-10 7:21 ` [tip/core/rcu, " Joel Fernandes
2018-05-10 13:15 ` Paul E. McKenney
2018-05-10 17:22 ` Joel Fernandes
2018-05-11 16:22 ` Paul E. McKenney
2018-05-10 17:37 ` Joel Fernandes
2018-05-11 16:24 ` Paul E. McKenney [this message]
2018-05-11 16:27 ` Joel Fernandes
2018-04-23 3:03 ` [PATCH tip/core/rcu 06/21] rcu: Avoid losing ->need_future_gp[] values due to GP start/end races Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 07/21] rcu: Make rcu_future_needs_gp() check all ->need_future_gps[] elements Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 08/21] rcu: Convert ->need_future_gp[] array to boolean Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 09/21] rcu: Make rcu_migrate_callbacks wake GP kthread when needed Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 10/21] rcu: Avoid __call_rcu_core() root rcu_node ->lock acquisition Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 11/21] rcu: Switch __rcu_process_callbacks() to rcu_accelerate_cbs() Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 12/21] rcu: Cleanup, don't put ->completed into an int Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 13/21] rcu: Clear request other than RCU_GP_FLAG_INIT at GP end Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 14/21] rcu: Inline rcu_start_gp_advanced() into rcu_start_future_gp() Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 15/21] rcu: Make rcu_start_future_gp() caller select grace period Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 16/21] rcu: Add funnel locking to rcu_start_this_gp() Paul E. McKenney
2018-05-12 6:03 ` [tip/core/rcu,16/21] " Joel Fernandes
2018-05-12 14:40 ` Paul E. McKenney
2018-05-12 14:44 ` Paul E. McKenney
2018-05-12 23:53 ` Joel Fernandes
2018-05-13 15:38 ` Paul E. McKenney
2018-05-13 16:49 ` Joel Fernandes
2018-05-13 19:09 ` Paul E. McKenney
2018-05-13 19:51 ` Joel Fernandes
2018-05-14 2:22 ` Paul E. McKenney
2018-05-14 5:00 ` Joel Fernandes
2018-05-14 13:23 ` Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 17/21] rcu: Make rcu_start_this_gp() check for out-of-range requests Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 18/21] rcu: The rcu_gp_cleanup() function does not need cpu_needs_another_gp() Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 19/21] rcu: Simplify and inline cpu_needs_another_gp() Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 20/21] rcu: Drop early GP request check from rcu_gp_kthread() Paul E. McKenney
2018-04-23 3:03 ` [PATCH tip/core/rcu 21/21] rcu: Update list of rcu_future_grace_period() trace events Paul E. McKenney
2018-05-14 6:42 ` [PATCH tip/core/rcu 0/21] Contention reduction for v4.18 Nicholas Piggin
2018-05-14 16:09 ` Paul E. McKenney
2018-05-14 22:21 ` Nicholas Piggin
2018-05-14 22:42 ` Paul E. McKenney
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