Hello folks, I'd like to put the patch below out for comments to see if folks think the approach is a valid fix to reduce the latency of synchronize_rcu(). The motivation is that an otherwise idle system takes about 3 ticks per network interface in unregister_netdev() due to multiple calls to synchronize_rcu(), which adds up to quite a few seconds for tearing down thousands of interfaces. By flushing pending rcu callbacks in the idle loop, the system makes progress hundreds of times faster. If this is indeed a sane thing to, it probably needs to be done for other architectures than x86. And yes, the network stack shouldn't call synchronize_rcu() quite so much, but fixing that is a little more involved. -ben diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 9663c2a..592f6e4 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -188,6 +188,9 @@ void cpu_idle(void) rmb(); idle = pm_idle; + if (rcu_pending(cpu)) + rcu_check_callbacks(cpu, 0); + if (!idle) idle = default_idle; - To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
