icmp_global_credit was meant to be changed ~1000 times per second, but if an admin sets net.ipv4.icmp_msgs_per_sec to a very high value, icmp_global_credit changes can inflict false sharing to surrounding fields that are read mostly. Move icmp_global_credit and icmp_global_stamp to a separate cacheline aligned group. Fixes: b056b4cd9178 ("icmp: move icmp_global.credit and icmp_global.stamp to per netns storage") Signed-off-by: Eric Dumazet --- include/net/netns/ipv4.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h index 2dbd46fc4734b78201818ecf6065237d475101ce..8e971c7bf164642344f40a07e021b0037f27ee7d 100644 --- a/include/net/netns/ipv4.h +++ b/include/net/netns/ipv4.h @@ -88,6 +88,12 @@ struct netns_ipv4 { int sysctl_tcp_rcvbuf_low_rtt; __cacheline_group_end(netns_ipv4_read_rx); + /* ICMP rate limiter hot cache line. */ + __cacheline_group_begin_aligned(icmp); + atomic_t icmp_global_credit; + u32 icmp_global_stamp; + __cacheline_group_end_aligned(icmp); + struct inet_timewait_death_row tcp_death_row; struct udp_table *udp_table; @@ -141,8 +147,7 @@ struct netns_ipv4 { int sysctl_icmp_ratemask; int sysctl_icmp_msgs_per_sec; int sysctl_icmp_msgs_burst; - atomic_t icmp_global_credit; - u32 icmp_global_stamp; + u32 ip_rt_min_pmtu; int ip_rt_mtu_expires; int ip_rt_min_advmss; -- 2.53.0.310.g728cabbaf7-goog