On Thu, 19 Feb 2009 15:56:18 -0800 Rick Jones <rick.jones2@xxxxxx> wrote: > Eric Dumazet wrote: > > Stephen Hemminger a écrit : > > > >>The reader/writer lock in ip_tables is acquired in the critical path of > >>processing packets and is one of the reasons just loading iptables can cause > >>a 20% performance loss. The rwlock serves two functions: > >> > >>1) it prevents changes to table state (xt_replace) while table is in use. > >> This is now handled by doing rcu on the xt_table. When table is > >> replaced, the new table(s) are put in and the old one table(s) are freed > >> after RCU period. > >> > >>2) it provides synchronization when accesing the counter values. > >> This is now handled by swapping in new table_info entries for each cpu > >> then summing the old values, and putting the result back onto one > >> cpu. On a busy system it may cause sampling to occur at different > >> times on each cpu, but no packet/byte counts are lost in the process. > >> > >>Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxxxx> > > > > > > > > Acked-by: Eric Dumazet <dada1@xxxxxxxxxxxxx> > > > > Sucessfully tested on my dual quad core machine too, but iptables only (no > > ipv6 here) > > > > BTW, my new "tbench 8" result is 2450 MB/s, (it was 2150 MB/s not so long ago) > > > > Thanks Stephen, thats very cool stuff, yet another rwlock out of kernel :) > > Do you folks need/want further testing against the 32-core setup? It would be good to combine all 3 (iptables-rcu, timer change, and conntrack lock) to see what the overhead change is. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
