From: "Paul E. McKenney" <[email protected]> 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, but in the meantime, this commit is one way to help locate them. Signed-off-by: Paul E. McKenney <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> --- kernel/cpu.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 42bd331..6b37ce0 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -247,13 +247,18 @@ static int __ref take_cpu_down(void *_param) { struct take_cpu_down_param *param = _param; int err; + unsigned long flags; /* Ensure this CPU doesn't handle any more interrupts. */ + local_irq_save(flags); err = __cpu_disable(); - if (err < 0) + if (err < 0) { + local_irq_restore(flags); return err; + } cpu_notify(CPU_DYING | param->mod, param->hcpu); + local_irq_restore(flags); return 0; } @@ -286,7 +291,7 @@ 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); -- 1.7.8 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
