From 87b08913a9ae82082e276d237ece08fc8ee24380 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 16 Feb 2026 14:28:29 +0000 Subject: [PATCH] inet: move icmp_global_{credit,stamp} to a separate cache line 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 Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260216142832.3834174-3-edumazet@google.com Signed-off-by: Jakub Kicinski --- 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 2dbd46fc4734..8e971c7bf164 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; -- 2.30.2