On Thu, Jan 13, 2011 at 7:04 AM, Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> wrote: > BTW, Nick: Given that some filesystems such as NFS are _always_ going to > reject LOOKUP_RCU, That's not very optimistic of you... why is that a given, my I ask? Or do you just mean as-in the current code? > it would appear to be completely out of place to use > the 'unlikely()' keyword when testing the results of path_walk_rcu() and > friends. In particular when the kernel is running with nfsroot, we're > saying that 100% of all cases are 'unlikely'... Well that _is_ an accepted use of branch annotations. For example it is used when scheduling realtime tasks, because even if some systems will do 99.9% of their scheduling on realtime tasks, it is not the common case. I'm not saying that applies here, but: if path walk performance is important, then we should use local caching and rcu-walk. If not, then why do we care about slightly slower branch? The annotations really help to reduce icache penalty of added complexity which is why I like them, but I'm happy to remove them where they don't make sense of course. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
