From: Eric Dumazet <[EMAIL PROTECTED]> Date: Thu, 01 Nov 2007 18:54:24 +0100
> Stephen Hemminger a écrit : > > Longterm is there any chance of using rcu for this? Seems like > > it could be a big win. > > This was discussed in the past, and I even believe some patch was proposed, > but some guys (including David) complained that RCU is well suited for > 'mostly > read' structures. > > On some web server workloads, TCP hash table is constantly accessed in write > mode (socket creation, socket move to timewait state, socket deleted...), > and > RCU added overhead and poor cache re-use (because sockets must be placed on > RCU queue before reuse) > > On these typical workload, hash table without RCU is still the best. Right, and none of the submitted RCU attempts were correct, it's very hard to get the synchronization right. > Longterm changes would rather be based on Robert Olsson suggestion > last year (trie based lookups and unified IP/TCP cache) > > Short term changes would be to be able to resize the TCP hash table (being > small at boot, and be able to grow it if necessary). Its current size on > modern machines is just insane. Resizing the hash is also, unfortunately, very hard to implement as well. - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
