From: Paul E. McKenney <paul.mcken...@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.mcken...@linaro.org> Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> [ srivatsa.b...@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.b...@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 5a63296..3f9498e 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -484,7 +484,7 @@ 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/