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SubjectRe: [PATCH] netfilter: use per-cpu spinlock rather than RCU (v3)
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 Dumazet.
> 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.
>
> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
>
> ---
> include/linux/netfilter/x_tables.h | 5 -
> net/ipv4/netfilter/arp_tables.c | 112 +++++++++------------------------
> net/ipv4/netfilter/ip_tables.c | 123 +++++++++++--------------------------
> net/ipv6/netfilter/ip6_tables.c | 119 +++++++++++------------------------
> net/netfilter/x_tables.c | 28 --------
> 5 files changed, 110 insertions(+), 277 deletions(-)
>

Tested successfuly on my dev machine, thanks Stephen.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>


"strace -tt -T iptables -L" on this 8 cpu machine show quite fast operations now
(sub 1/HZ)

23:37:26.629489 getsockopt(3, SOL_IP, 0x40 /* IP_??? */, "filter\0\300\\\236@\365\271\231\"\300`\225T\367\1\0\0\0\0vm\300`\225T\367\
16"..., [84]) = 0 <0.000008>
23:37:26.629579 brk(0) = 0x8054000 <0.000006>
23:37:26.629613 brk(0x8075000) = 0x8075000 <0.000007>
23:37:26.629660 getsockopt(3, SOL_IP, 0x41 /* IP_??? */, "filter\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0L"..., [10608])
= 0 <0.000031>
23:37:26.629772 fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0 <0.000007>

same fast operation for an "iptables -A INPUT" operation


23:37:02.180313 close(4) = 0 <0.000006>
23:37:02.180382 setsockopt(3, SOL_IP, 0x40 /* IP_??? */, "filter\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\16"..., 10664)
= 0 <0.000114>
23:37:02.180552 setsockopt(3, SOL_IP, 0x41 /* IP_??? */, "filter\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\20"..., 292) =
0 <0.000015>
23:37:02.180635 close(3) = 0 <0.000010>

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