From: Josh Triplett <josh@joshtriplett.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org
Subject: Re: [PATCH tip/core/rcu 04/23] rcu: Allow RCU grace-period cleanup to be preempted
Date: Sat, 1 Sep 2012 18:36:31 -0700 [thread overview]
Message-ID: <20120902013631.GD5713@leaf> (raw)
In-Reply-To: <1346350718-30937-4-git-send-email-paulmck@linux.vnet.ibm.com>
On Thu, Aug 30, 2012 at 11:18:19AM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> RCU grace-period cleanup is currently carried out with interrupts
> disabled, which can result in excessive latency spikes on large systems
> (many hundreds or thousands of CPUs). This patch therefore makes the
> RCU grace-period cleanup be preemptible, including voluntary preemption
> points, which should eliminate those latency spikes. Similar spikes from
> forcing of quiescent states will be dealt with similarly by later patches.
>
> Reported-by: Mike Galbraith <mgalbraith@suse.de>
> Reported-by: Dimitri Sivanich <sivanich@sgi.com>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
> kernel/rcutree.c | 11 +++++------
> 1 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index 9fad21c..300aba6 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -1170,7 +1170,7 @@ static int rcu_gp_kthread(void *arg)
> * completed.
> */
> if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {
> - raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
> + raw_spin_unlock_irqrestore(&rnp->lock, flags);
>
> /*
> * Propagate new ->completed value to rcu_node
> @@ -1179,14 +1179,13 @@ static int rcu_gp_kthread(void *arg)
> * to process their callbacks.
> */
> rcu_for_each_node_breadth_first(rsp, rnp) {
> - /* irqs already disabled. */
> - raw_spin_lock(&rnp->lock);
> + raw_spin_lock_irqsave(&rnp->lock, flags);
> rnp->completed = rsp->gpnum;
> - /* irqs remain disabled. */
> - raw_spin_unlock(&rnp->lock);
> + raw_spin_unlock_irqrestore(&rnp->lock, flags);
> + cond_resched();
> }
> rnp = rcu_get_root(rsp);
> - raw_spin_lock(&rnp->lock); /* irqs already disabled. */
> + raw_spin_lock_irqsave(&rnp->lock, flags);
> }
>
> rsp->completed = rsp->gpnum; /* Declare grace period done. */
> --
> 1.7.8
>
next prev parent reply other threads:[~2012-09-02 1:36 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-30 18:18 [PATCH tip/core/rcu 0/23] Improvements to RT response on big systems and expedited functions Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 01/23] rcu: Move RCU grace-period initialization into a kthread Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 02/23] rcu: Allow RCU grace-period initialization to be preempted Paul E. McKenney
2012-09-02 1:09 ` Josh Triplett
2012-09-05 1:22 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 03/23] rcu: Move RCU grace-period cleanup into kthread Paul E. McKenney
2012-09-02 1:22 ` Josh Triplett
2012-09-06 13:34 ` Peter Zijlstra
2012-09-06 17:29 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 04/23] rcu: Allow RCU grace-period cleanup to be preempted Paul E. McKenney
2012-09-02 1:36 ` Josh Triplett [this message]
2012-08-30 18:18 ` [PATCH tip/core/rcu 05/23] rcu: Prevent offline CPUs from executing RCU core code Paul E. McKenney
2012-09-02 1:45 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 06/23] rcu: Break up rcu_gp_kthread() into subfunctions Paul E. McKenney
2012-09-02 2:11 ` Josh Triplett
2012-09-06 13:39 ` Peter Zijlstra
2012-09-06 17:32 ` Paul E. McKenney
2012-09-06 18:49 ` Josh Triplett
2012-09-06 19:09 ` Peter Zijlstra
2012-09-06 20:30 ` Paul E. McKenney
2012-09-06 20:30 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 07/23] rcu: Provide OOM handler to motivate lazy RCU callbacks Paul E. McKenney
2012-09-02 2:13 ` Josh Triplett
2012-09-03 9:08 ` Lai Jiangshan
2012-09-05 17:45 ` Paul E. McKenney
2012-09-06 13:46 ` Peter Zijlstra
2012-09-06 13:52 ` Steven Rostedt
2012-09-06 17:41 ` Paul E. McKenney
2012-09-06 17:46 ` Peter Zijlstra
2012-09-06 20:32 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 08/23] rcu: Segregate rcu_state fields to improve cache locality Paul E. McKenney
2012-09-02 2:51 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 09/23] rcu: Move quiescent-state forcing into kthread Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 10/23] rcu: Allow RCU quiescent-state forcing to be preempted Paul E. McKenney
2012-09-02 5:23 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 11/23] rcu: Adjust debugfs tracing for kthread-based quiescent-state forcing Paul E. McKenney
2012-09-02 6:05 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 12/23] rcu: Prevent force_quiescent_state() memory contention Paul E. McKenney
2012-09-02 10:47 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 13/23] rcu: Control grace-period duration from sysfs Paul E. McKenney
2012-09-03 9:30 ` Josh Triplett
2012-09-03 9:31 ` Josh Triplett
2012-09-06 14:15 ` Peter Zijlstra
2012-09-06 17:53 ` Paul E. McKenney
2012-09-06 18:28 ` Peter Zijlstra
2012-09-06 20:37 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 14/23] rcu: Remove now-unused rcu_state fields Paul E. McKenney
2012-09-03 9:31 ` Josh Triplett
2012-09-06 14:17 ` Peter Zijlstra
2012-09-06 18:02 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 15/23] rcu: Make rcutree module parameters visible in sysfs Paul E. McKenney
2012-09-03 9:32 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 16/23] rcu: Prevent initialization-time quiescent-state race Paul E. McKenney
2012-09-03 9:37 ` Josh Triplett
2012-09-05 18:19 ` Paul E. McKenney
2012-09-05 18:55 ` Josh Triplett
2012-09-05 19:49 ` Paul E. McKenney
2012-09-06 14:21 ` Peter Zijlstra
2012-09-06 16:18 ` Paul E. McKenney
2012-09-06 16:22 ` Peter Zijlstra
2012-08-30 18:18 ` [PATCH tip/core/rcu 17/23] rcu: Fix day-zero grace-period initialization/cleanup race Paul E. McKenney
2012-09-03 9:39 ` Josh Triplett
2012-09-06 14:24 ` Peter Zijlstra
2012-09-06 18:06 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 18/23] rcu: Add random PROVE_RCU_DELAY to grace-period initialization Paul E. McKenney
2012-09-03 9:41 ` Josh Triplett
2012-09-06 14:27 ` Peter Zijlstra
2012-09-06 18:25 ` Paul E. McKenney
2012-08-30 18:18 ` [PATCH tip/core/rcu 19/23] rcu: Adjust for unconditional ->completed assignment Paul E. McKenney
2012-09-03 9:42 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 20/23] rcu: Remove callback acceleration from grace-period initialization Paul E. McKenney
2012-09-03 9:42 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 21/23] rcu: Eliminate signed overflow in synchronize_rcu_expedited() Paul E. McKenney
2012-09-03 9:43 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 22/23] rcu: Reduce synchronize_rcu_expedited() latency Paul E. McKenney
2012-09-03 9:46 ` Josh Triplett
2012-08-30 18:18 ` [PATCH tip/core/rcu 23/23] rcu: Simplify quiescent-state detection Paul E. McKenney
2012-09-03 9:56 ` Josh Triplett
2012-09-06 14:36 ` Peter Zijlstra
2012-09-06 20:01 ` Paul E. McKenney
2012-09-06 21:18 ` Mathieu Desnoyers
2012-09-06 21:31 ` Paul E. McKenney
2012-09-02 1:04 ` [PATCH tip/core/rcu 01/23] rcu: Move RCU grace-period initialization into a kthread Josh Triplett
2012-09-06 13:32 ` Peter Zijlstra
2012-09-06 17:00 ` Paul E. McKenney
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