Messages in this thread | | | Date | Mon, 13 Apr 2009 19:40:24 +0200 | From | Eric Dumazet <> | Subject | Re: [PATCH] netfilter: use per-cpu spinlock rather than RCU |
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Stephen Hemminger a écrit : > This is an alternative version of ip/ip6/arp tables locking using > per-cpu locks. This avoids the overhead of synchronize_net() during > update but still removes the expensive rwlock in earlier versions. > > The idea for this came from an earlier version done by Eric Duzamet. > Locking is done per-cpu, the fast path locks on the current cpu > and updates counters. The slow case involves acquiring the locks on > all cpu's. > > The mutex that was added for 2.6.30 in xt_table is unnecessary since > there already is a mutex for xt[af].mutex that is held. > > Tested basic functionality (add/remove/list), but don't have test cases > for stress, ip6tables or arptables. > > Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Patch seems good to me, but apparently xt_replace_table() misses the "acquiring the locks on all cpus" you mentioned in ChangeLog ?
I am still off-computers until tomorrow so cannot provide a patch for this, sorry.
Some form of
local_bh_disable(); for_each_possible_cpu(cpu) spin_lock(&per_cpu(ip_tables_lock, cpu));
oldinfo = private; /* do the substitution */ table->private = newinfo; newinfo->initial_entries = oldinfo->initial_entries;
for_each_possible_cpu(cpu) spin_unlock(&per_cpu(ip_tables_lock, cpu)); local_bh_enable();
But I wonder if this could hit a limit of max spinlocks held by this cpu, say on a 4096 cpu machine ?
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