On Tue, 2016-11-01 at 00:57 +0200, Ido Schimmel wrote: > On Mon, Oct 31, 2016 at 02:24:06PM -0700, Eric Dumazet wrote:
> > How well will this work for large FIB tables ? > > > > Holding rtnl while sending thousands of skb will prevent consumers to > > make progress ? > > Can you please clarify what do you mean by "while sending thousands of > skb"? This patch doesn't generate notifications to user space, but > instead invokes notification routines inside the kernel. I probably > misunderstood you. > > Are you suggesting this be done using RCU instead? Well, there are a > couple of reasons why I took RTNL here: > No, I do not believe RCU is wanted here, in control path where we might sleep anyway. > 1) The FIB notification chain is blocking, so listeners are expected to > be able to sleep. This isn't possible if we use RCU. Note that this > chain is mainly useful for drivers that reflect the FIB table into a > capable device and hardware operations usually involve sleeping. > > 2) The insertion of a single route is done with RTNL held. I didn't want > to differentiate between both cases. This property is really useful for > listeners, as they don't need to worry about locking in writer-side. > Access to data structs is serialized by RTNL. My concern was that for large iterations, you might hold RTNL and/or current cpu for hundred of ms or even seconds...
