From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: tglx@linutronix.de, peterz@infradead.org,
paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au,
mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org,
vincent.guittot@linaro.org, tj@kernel.org, oleg@redhat.com
Cc: sbw@mit.edu, amit.kucheria@linaro.org, rostedt@goodmis.org,
rjw@sisk.pl, srivatsa.bhat@linux.vnet.ibm.com,
wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com,
nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [RFC PATCH v2 10/10] cpu: No more __stop_machine() in _cpu_down()
Date: Thu, 06 Dec 2012 00:15:00 +0530 [thread overview]
Message-ID: <20121205184456.3750.35005.stgit@srivatsabhat.in.ibm.com> (raw)
In-Reply-To: <20121205184041.3750.64945.stgit@srivatsabhat.in.ibm.com>
From: Paul E. McKenney <paul.mckenney@linaro.org>
The _cpu_down() function invoked as part of the CPU-hotplug offlining
process currently invokes __stop_machine(), which is slow and inflicts
substantial real-time latencies on the entire system. This patch
substitutes stop_cpus() for __stop_machine() in order to improve
both performance and real-time latency.
This is currently unsafe, because there are a number of uses of
preempt_disable() that are intended to block CPU-hotplug offlining.
These will be fixed by using get/put_online_cpus_atomic_light(), or
get/put_online_cpus_atomic_full(), but in the meantime, this commit is one
way to help locate them.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ Srivatsa: Refer to the new sync primitives for readers, in the changelog ]
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
---
kernel/cpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index c71c723..00a1edc 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -418,7 +418,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
}
smpboot_park_threads(cpu);
- err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
+ err = stop_cpus(cpumask_of(cpu), take_cpu_down, &tcd_param);
if (err) {
/* CPU didn't die: tell everyone. Can't complain. */
smpboot_unpark_threads(cpu);
next prev parent reply other threads:[~2012-12-05 18:46 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-05 18:42 [RFC PATCH v2 00/10][RESEND] CPU hotplug: stop_machine()-free CPU hotplug Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 01/10] CPU hotplug: Provide APIs for "light" atomic readers to prevent CPU offline Srivatsa S. Bhat
2012-12-05 18:47 ` Srivatsa S. Bhat
2012-12-05 18:51 ` Srivatsa S. Bhat
2012-12-05 18:53 ` Srivatsa S. Bhat
2012-12-05 18:56 ` Srivatsa S. Bhat
2012-12-05 18:59 ` Srivatsa S. Bhat
2012-12-05 20:14 ` Srivatsa S. Bhat
2012-12-06 16:18 ` Oleg Nesterov
2012-12-06 18:48 ` Srivatsa S. Bhat
2012-12-06 19:17 ` Srivatsa S. Bhat
2012-12-07 21:01 ` Oleg Nesterov
2012-12-06 19:28 ` Steven Rostedt
2012-12-06 19:36 ` Srivatsa S. Bhat
2012-12-06 22:02 ` Steven Rostedt
2012-12-07 17:33 ` Srivatsa S. Bhat
[not found] ` <20121207200014.GB13238@redhat.com>
2012-12-10 18:21 ` Oleg Nesterov
2012-12-10 19:07 ` Steven Rostedt
2012-12-07 19:56 ` Oleg Nesterov
2012-12-07 20:25 ` Srivatsa S. Bhat
2012-12-07 20:59 ` Oleg Nesterov
2012-12-05 19:07 ` Oleg Nesterov
2012-12-05 19:16 ` Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 02/10] CPU hotplug: Provide APIs for "full" " Srivatsa S. Bhat
2012-12-05 19:01 ` Srivatsa S. Bhat
2012-12-05 20:31 ` Srivatsa S. Bhat
2012-12-05 20:57 ` Tejun Heo
2012-12-06 4:31 ` Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 03/10] CPU hotplug: Convert preprocessor macros to static inline functions Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 04/10] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Srivatsa S. Bhat
2012-12-05 18:43 ` [RFC PATCH v2 05/10] smp, cpu hotplug: Fix on_each_cpu_*() " Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 06/10] sched, cpu hotplug: Use stable online cpus in try_to_wake_up() & select_task_rq() Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 07/10] kick_process(), cpu-hotplug: Prevent offlining of target CPU properly Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 08/10] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly Srivatsa S. Bhat
2012-12-05 18:44 ` [RFC PATCH v2 09/10] kvm, vmx: Add full atomic synchronization with CPU Hotplug Srivatsa S. Bhat
2012-12-05 18:45 ` Srivatsa S. Bhat [this message]
2012-12-05 19:08 ` [RFC PATCH v2 10/10] cpu: No more __stop_machine() in _cpu_down() Oleg Nesterov
2012-12-05 19:12 ` Srivatsa S. Bhat
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