From: Jakub Kicinski Date: Wed, 2 Jul 2025 21:22:04 +0000 (-0700) Subject: Merge branch 'net-introduce-net_aligned_data' X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8077b9a911d7cb0f606217f645d82c7b083ca238;p=thirdparty%2Flinux.git Merge branch 'net-introduce-net_aligned_data' Eric Dumazet says: ==================== net: introduce net_aligned_data ____cacheline_aligned_in_smp on small fields like tcp_memory_allocated and udp_memory_allocated is not good enough. It makes sure to put these fields at the start of a cache line, but does not prevent the linker from using the cache line for other fields, with potential performance impact. nm -v vmlinux|egrep -5 "tcp_memory_allocated|udp_memory_allocated" ... ffffffff83e35cc0 B tcp_memory_allocated ffffffff83e35cc8 b __key.0 ffffffff83e35cc8 b __tcp_tx_delay_enabled.1 ffffffff83e35ce0 b tcp_orphan_timer ... ffffffff849dddc0 B udp_memory_allocated ffffffff849dddc8 B udp_encap_needed_key ffffffff849dddd8 B udpv6_encap_needed_key ffffffff849dddf0 b inetsw_lock One solution is to move these sensitive fields to a structure, so that the compiler is forced to add empty holes between each member. nm -v vmlinux|egrep -2 "tcp_memory_allocated|udp_memory_allocated|net_aligned_data" ffffffff885af970 b mem_id_init ffffffff885af980 b __key.0 ffffffff885af9c0 B net_aligned_data ffffffff885afa80 B page_pool_mem_providers ffffffff885afa90 b __key.2 v1: https://lore.kernel.org/netdev/20250627200551.348096-1-edumazet@google.com/ ==================== Link: https://patch.msgid.link/20250630093540.3052835-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- 8077b9a911d7cb0f606217f645d82c7b083ca238