From: Benjamin LaHaise Date: Wed, 30 Jan 2008 12:33:13 +0000 (+0100) Subject: x86: fix synchronize_rcu(): high latency on idle system X-Git-Tag: v2.6.25-rc1~1143^2~283 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0723a69a63beec1ca6e792239ef75d0181387ef0;p=linux-2.6 x86: fix synchronize_rcu(): high latency on idle system 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. Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 7a61b54649..69a69c3f43 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -198,6 +198,9 @@ void cpu_idle(void) rmb(); idle = pm_idle; + if (rcu_pending(cpu)) + rcu_check_callbacks(cpu, 0); + if (!idle) idle = default_idle;