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inet: move icmp_global_{credit,stamp} to a separate cache line

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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: b056b4cd91 ("icmp: move icmp_global.credit and icmp_global.stamp to per netns storage")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260216142832.3834174-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet
2026-02-16 14:28:29 +00:00
committed by Jakub Kicinski
parent 034bbd8062
commit 87b08913a9
1 changed files with 7 additions and 2 deletions
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9
include/net/netns/ipv4.h
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@@ -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;