diff options
| author | Eric Dumazet <edumazet@google.com> | 2025-09-09 12:19:42 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-09-14 11:35:17 -0700 |
| commit | fdae0ab67d57d480dc61e9fb45678bbdc3786711 (patch) | |
| tree | 9a45268e106c211e75c55a285db8569a9849747b /include/linux/netdevice.h | |
| parent | 278289bcec901663868048497e36c92560bd1b14 (diff) | |
net: use NUMA drop counters for softnet_data.dropped
Hosts under DOS attack can suffer from false sharing
in enqueue_to_backlog() : atomic_inc(&sd->dropped).
This is because sd->dropped can be touched from many cpus,
possibly residing on different NUMA nodes.
Generalize the sk_drop_counters infrastucture
added in commit c51613fa276f ("net: add sk->sk_drop_counters")
and use it to replace softnet_data.dropped
with NUMA friendly softnet_data.drop_counters.
This adds 64 bytes per cpu, maybe more in the future
if we increase the number of counters (currently 2)
per 'struct numa_drop_counters'.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250909121942.1202585-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'include/linux/netdevice.h')
| -rw-r--r-- | include/linux/netdevice.h | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index f3a3b761abfb..f5a840c07cf1 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3459,6 +3459,32 @@ static inline bool dev_has_header(const struct net_device *dev) return dev->header_ops && dev->header_ops->create; } +struct numa_drop_counters { + atomic_t drops0 ____cacheline_aligned_in_smp; + atomic_t drops1 ____cacheline_aligned_in_smp; +}; + +static inline int numa_drop_read(const struct numa_drop_counters *ndc) +{ + return atomic_read(&ndc->drops0) + atomic_read(&ndc->drops1); +} + +static inline void numa_drop_add(struct numa_drop_counters *ndc, int val) +{ + int n = numa_node_id() % 2; + + if (n) + atomic_add(val, &ndc->drops1); + else + atomic_add(val, &ndc->drops0); +} + +static inline void numa_drop_reset(struct numa_drop_counters *ndc) +{ + atomic_set(&ndc->drops0, 0); + atomic_set(&ndc->drops1, 0); +} + /* * Incoming packets are placed on per-CPU queues */ @@ -3504,7 +3530,7 @@ struct softnet_data { struct sk_buff_head input_pkt_queue; struct napi_struct backlog; - atomic_t dropped ____cacheline_aligned_in_smp; + struct numa_drop_counters drop_counters; /* Another possibly contended cache line */ spinlock_t defer_lock ____cacheline_aligned_in_smp; |