On Saturday 12 January 2008 10:23:11 Peter Zijlstra wrote: > > On Fri, 2008-01-11 at 20:26 -0500, Benjamin LaHaise wrote: > > 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. > > So, instead of only relying on the tick to drive the RCU state machine, > you add the idle loop to it. This seems to make sense, esp because nohz > is held off until rcu is idle too. For NOHZ I agree it would be probably better to just force a quiescent cycle than to schedule a one jiffie tick like it is currently done. For non NOHZ I'm not so sure. -Andi - 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
