dev->state can be read in rx and tx fast paths.
netif_running() which needs dev->state is called from
- enqueue_to_backlog() [RX path]
- __dev_direct_xmit() [TX path]
Fixes: 43a71cd66b ("net-device: reorganize net_device fast path variables")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240314200845.3050179-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
The fast path usage breakdown describes the detail for 'inet_sock', fix
the markup title.
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
dev->lstats is notably used from loopback ndo_start_xmit()
and other virtual drivers.
Per cpu stats updates are dirtying per-cpu data,
but the pointer itself is read-only.
Fixes: 43a71cd66b ("net-device: reorganize net_device fast path variables")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Cc: Simon Horman <horms@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
tp->tcp_usec_ts is a read mostly field, used in rx and tx fast paths.
Fixes: d5fed5addb ("tcp: reorganize tcp_sock fast path variables")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Cc: Wei Wang <weiwan@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
tp->scaling_ratio is a read mostly field, used in rx and tx fast paths.
Fixes: d5fed5addb ("tcp: reorganize tcp_sock fast path variables")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Cc: Wei Wang <weiwan@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
xdp_prog is used in receive path, both from XDP enabled drivers
and from netif_elide_gro().
This patch also removes two 4-bytes holes.
Fixes: 43a71cd66b ("net-device: reorganize net_device fast path variables")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Cc: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240102162220.750823-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
dev->gso_partial_features is read from tx fast path for GSO packets.
Move it to appropriate section to avoid a cache line miss.
Fixes: 43a71cd66b ("net-device: reorganize net_device fast path variables")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Coco Li <lixiaoyan@google.com>
Cc: David Ahern <dsahern@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Analyzed a few structs in the networking stack by looking at variables
within them that are used in the TCP/IP fast path.
Fast path is defined as TCP path where data is transferred from sender to
receiver unidirectionally. It doesn't include phases other than
TCP_ESTABLISHED, nor does it look at error paths.
We hope to re-organizing variables that span many cachelines whose fast
path variables are also spread out, and this document can help future
developers keep networking fast path cachelines small.
Optimized_cacheline field is computed as
(Fastpath_Bytes/L3_cacheline_size_x86), and not the actual organized
results (see patches to come for these).
Investigation is done on 6.5
Name Struct_Cachelines Cur_fastpath_cache Fastpath_Bytes Optimized_cacheline
tcp_sock 42 (2664 Bytes) 12 396 8
net_device 39 (2240 bytes) 12 234 4
inet_sock 15 (960 bytes) 14 922 14
Inet_connection_sock 22 (1368 bytes) 18 1166 18
Netns_ipv4 (sysctls) 12 (768 bytes) 4 77 2
linux_mib 16 (1060) 6 104 2
Note how there isn't much improvement space for inet_sock and
Inet_connection_sock because sk and icsk_inet respectively takes up so
much of the struct that rest of the variables become a small portion of
the struct size.
So, we decided to reorganize tcp_sock, net_device, netns_ipv4
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Coco Li <lixiaoyan@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Eric Dumazet