On Thu, 2008-07-24 at 02:20 -0700, David Miller wrote: > From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Date: Thu, 24 Jul 2008 11:10:48 +0200 > > > Ok, then how about something like this, the idea is to wrap the per tx > > lock with a read lock of the device and let the netif_tx_lock() be the > > write side, therefore excluding all device locks, but not incure the > > cacheline bouncing on the read side by using per-cpu counters like rcu > > does. > > > > This of course requires that netif_tx_lock() is rare, otherwise stuff > > will go bounce anyway... > > > > Probably missed a few details,.. but I think the below ought to show the > > idea... > > Thanks for the effort, but I don't think we can seriously consider > this. > > This lock is taken for every packet transmitted by the system, adding > another memory reference (the RCU deref) and a counter bump is just > not something we can just add to placate lockdep. We going through > all of this effort to seperate the TX locking into individual > queues, it would be silly to go back and make it more expensive. Well, not only lockdep, taking a very large number of locks is expensive as well. > I have other ideas which I've expanded upon in other emails. They > involve creating a netif_tx_freeze() interface and getting the drivers > to start using it. OK, as long as we get there :-) -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
