kernel/linux.git/net/core/hotdata.c, branch v6.19.11

net: add net.core.qdisc_max_burst

2026-01-13T09:12:11+00:00

In blamed commit, I added a check against the temporary queue built in __dev_xmit_skb(). Idea was to drop packets early, before any spinlock was acquired. if (unlikely(defer_count > READ_ONCE(q->limit))) { kfree_skb_reason(skb, SKB_DROP_REASON_QDISC_DROP); return NET_XMIT_DROP; } It turned out that HTB Qdisc has a zero q->limit. HTB limits packets on a per-class basis. Some of our tests became flaky. Add a new sysctl : net.core.qdisc_max_burst to control how many packets can be stored in the temporary lockless queue. Also add a new QDISC_BURST_DROP drop reason to better diagnose future issues. Thanks Neal ! Fixes: 100dfa74cad9 ("net: dev_queue_xmit() llist adoption") Reported-and-bisected-by: Neal Cardwell Signed-off-by: Eric Dumazet Reviewed-by: Neal Cardwell Link: https://patch.msgid.link/20260107104159.3669285-1-edumazet@google.com Signed-off-by: Paolo Abeni

net: increase skb_defer_max default to 128

2025-11-08T03:02:40+00:00

skb_defer_max value is very conservative, and can be increased to avoid too many calls to kick_defer_list_purge(). Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Reviewed-by: Toke Høiland-Jørgensen Reviewed-by: Jason Xing Link: https://patch.msgid.link/20251106202935.1776179-4-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: move tcp_memory_allocated into net_aligned_data

2025-07-02T21:22:02+00:00

____cacheline_aligned_in_smp attribute only makes sure to align a field to a cache line. It does not prevent the linker to use the remaining of the cache line for other variables, causing potential false sharing. Move tcp_memory_allocated into a dedicated cache line. Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250630093540.3052835-4-edumazet@google.com Signed-off-by: Jakub Kicinski

net: add struct net_aligned_data

2025-07-02T21:22:02+00:00

This structure will hold networking data that must consume a full cache line to avoid accidental false sharing. Signed-off-by: Eric Dumazet Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20250630093540.3052835-2-edumazet@google.com Signed-off-by: Jakub Kicinski

net: introduce per netns packet chains

2025-03-24T20:58:22+00:00

Currently network taps unbound to any interface are linked in the global ptype_all list, affecting the performance in all the network namespaces. Add per netns ptypes chains, so that in the mentioned case only the netns owning the packet socket(s) is affected. While at that drop the global ptype_all list: no in kernel user registers a tap on "any" type without specifying either the target device or the target namespace (and IMHO doing that would not make any sense). Note that this adds a conditional in the fast path (to check for per netns ptype_specific list) and increases the dataset size by a cacheline (owing the per netns lists). Reviewed-by: Sabrina Dubroca Signed-off-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/ae405f98875ee87f8150c460ad162de7e466f8a7.1742494826.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski

net: move sysctl_mem_pcpu_rsv to net_hotdata

2024-05-01T01:46:52+00:00

sysctl_mem_pcpu_rsv is used in TCP fast path, move it to net_hodata for better cache locality. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20240429134025.1233626-6-edumazet@google.com Signed-off-by: Jakub Kicinski

net: move sysctl_skb_defer_max to net_hotdata

2024-05-01T01:46:52+00:00

sysctl_skb_defer_max is used in TCP fast path, move it to net_hodata. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20240429134025.1233626-3-edumazet@google.com Signed-off-by: Jakub Kicinski

net: move sysctl_max_skb_frags to net_hotdata

2024-05-01T01:46:52+00:00

sysctl_max_skb_frags is used in TCP and MPTCP fast paths, move it to net_hodata for better cache locality. Signed-off-by: Eric Dumazet Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20240429134025.1233626-2-edumazet@google.com Signed-off-by: Jakub Kicinski

net: move dev_rx_weight to net_hotdata

2024-03-08T05:12:42+00:00

dev_rx_weight is read from process_backlog(). Move it to net_hotdata for better cache locality. Signed-off-by: Eric Dumazet Acked-by: Soheil Hassas Yeganeh Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20240306160031.874438-10-edumazet@google.com Signed-off-by: Jakub Kicinski

net: move dev_tx_weight to net_hotdata

2024-03-08T05:12:42+00:00

dev_tx_weight is used in tx fast path. Move it to net_hotdata for better cache locality. Signed-off-by: Eric Dumazet Acked-by: Soheil Hassas Yeganeh Reviewed-by: David Ahern Link: https://lore.kernel.org/r/20240306160031.874438-9-edumazet@google.com Signed-off-by: Jakub Kicinski