From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.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, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH tip/core/rcu 04/18] rcu: Use single-stage IPI algorithm for RCU expedited grace period
Date: Wed, 7 Oct 2015 09:14:45 -0700 [thread overview]
Message-ID: <20151007161445.GN3910@linux.vnet.ibm.com> (raw)
In-Reply-To: <20151007134929.GM11639@twins.programming.kicks-ass.net>
On Wed, Oct 07, 2015 at 03:49:29PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 07, 2015 at 03:43:11PM +0200, Peter Zijlstra wrote:
> > On Tue, Oct 06, 2015 at 09:29:23AM -0700, Paul E. McKenney wrote:
> > > @@ -167,42 +307,18 @@ static void rcu_preempt_note_context_switch(void)
> >
> > > - raw_spin_unlock_irqrestore(&rnp->lock, flags);
> >
> > This again reminds me that we should move rcu_note_context_switch()
> > under the IRQ disable section the scheduler already has or remove the
> > IRQ disable from rcu_note_context_switch().
>
> Ah, this is the unlikely path where we actually need to do work. The
> normal fast paths no longer require IRQs disabled, you already fixed
> that last time, good!
But why not make the less-likely paths a bit cheaper while we are at it? ;-)
Thanx, Paul
next prev parent reply other threads:[~2015-10-07 16:14 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-06 16:29 [PATCH tip/core/rcu 0/18] Expedited grace-period improvements for 4.4 Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 01/18] rcu: Use rsp->expedited_wq instead of sync_rcu_preempt_exp_wq Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 02/18] rcu: Move rcu_report_exp_rnp() to allow consolidation Paul E. McKenney
2015-10-06 20:29 ` Peter Zijlstra
2015-10-06 20:58 ` Paul E. McKenney
2015-10-07 7:51 ` Peter Zijlstra
2015-10-07 8:42 ` Mathieu Desnoyers
2015-10-07 11:01 ` Peter Zijlstra
2015-10-07 11:50 ` Peter Zijlstra
2015-10-07 12:03 ` Peter Zijlstra
2015-10-07 12:05 ` kbuild test robot
2015-10-07 12:09 ` kbuild test robot
2015-10-07 12:11 ` kbuild test robot
2015-10-07 12:17 ` Peter Zijlstra
2015-10-07 13:44 ` [kbuild-all] " Fengguang Wu
2015-10-07 13:55 ` Peter Zijlstra
2015-10-07 14:21 ` Fengguang Wu
2015-10-07 14:28 ` Peter Zijlstra
2015-10-07 15:18 ` Paul E. McKenney
2015-10-08 10:24 ` Peter Zijlstra
2015-10-07 15:15 ` Paul E. McKenney
2015-10-07 14:33 ` Paul E. McKenney
2015-10-07 14:40 ` Peter Zijlstra
2015-10-07 16:48 ` Paul E. McKenney
2015-10-08 9:49 ` Peter Zijlstra
2015-10-08 15:33 ` Paul E. McKenney
2015-10-08 17:12 ` Peter Zijlstra
2015-10-08 17:46 ` Paul E. McKenney
2015-10-09 0:10 ` Paul E. McKenney
2015-10-09 8:44 ` Peter Zijlstra
2015-10-06 16:29 ` [PATCH tip/core/rcu 03/18] rcu: Consolidate tree setup for synchronize_rcu_expedited() Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 04/18] rcu: Use single-stage IPI algorithm for RCU expedited grace period Paul E. McKenney
2015-10-07 13:24 ` Peter Zijlstra
2015-10-07 18:11 ` Paul E. McKenney
2015-10-07 13:35 ` Peter Zijlstra
2015-10-07 15:44 ` Paul E. McKenney
2015-10-07 13:43 ` Peter Zijlstra
2015-10-07 13:49 ` Peter Zijlstra
2015-10-07 16:14 ` Paul E. McKenney [this message]
2015-10-08 9:00 ` Peter Zijlstra
2015-10-07 16:13 ` Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 05/18] rcu: Move synchronize_sched_expedited() to combining tree Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 06/18] rcu: Rename qs_pending to core_needs_qs Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 07/18] rcu: Invert passed_quiesce and rename to cpu_no_qs Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 08/18] rcu: Make ->cpu_no_qs be a union for aggregate OR Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 09/18] rcu: Switch synchronize_sched_expedited() to IPI Paul E. McKenney
2015-10-07 14:18 ` Peter Zijlstra
2015-10-07 16:24 ` Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 10/18] rcu: Stop silencing lockdep false positive for expedited grace periods Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 11/18] rcu: Stop excluding CPU hotplug in synchronize_sched_expedited() Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 12/18] cpu: Remove try_get_online_cpus() Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 13/18] rcu: Prepare for consolidating expedited CPU selection Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 14/18] rcu: Consolidate " Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 15/18] rcu: Add online/offline info to expedited stall warning message Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 16/18] rcu: Add tasks to expedited stall-warning messages Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 17/18] rcu: Enable stall warnings for synchronize_rcu_expedited() Paul E. McKenney
2015-10-06 16:29 ` [PATCH tip/core/rcu 18/18] rcu: Better hotplug handling for synchronize_sched_expedited() Paul E. McKenney
2015-10-07 14:26 ` Peter Zijlstra
2015-10-07 16:26 ` Paul E. McKenney
2015-10-08 9:01 ` Peter Zijlstra
2015-10-08 15:06 ` Paul E. McKenney
2015-10-08 15:12 ` Peter Zijlstra
2015-10-08 15:19 ` Paul E. McKenney
2015-10-08 18:01 ` Josh Triplett
2015-10-09 0:11 ` Paul E. McKenney
2015-10-09 0:48 ` Josh Triplett
2015-10-09 3:54 ` Paul E. McKenney
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