Messages in this thread Patch in this message | | | From | "Srivatsa S. Bhat" <> | Subject | [RFC PATCH v3 9/9] cpu: No more __stop_machine() in _cpu_down() | Date | Fri, 07 Dec 2012 23:10:23 +0530 |
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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_one_cpu() 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(), 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.bhat@linux.vnet.ibm.com: Refer to the new sync primitives for readers (in the changelog), and s/stop_cpus/stop_one_cpu ] 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 d2076fa..71c65dc 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -532,7 +532,7 @@ 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_one_cpu(cpu, take_cpu_down, &tcd_param); if (err) { /* CPU didn't die: tell everyone. Can't complain. */ smpboot_unpark_threads(cpu);
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