[PATCH 1/4] NET : defines an infrastructure to keep 'inuse' changes in an efficent SMP/NUMA way.

"struct proto" currently uses an array stats[NR_CPUS] to track change on 
'inuse' sockets per protocol.

If NR_CPUS is big, this means we use a big memory area for this.
Moreover, all this memory area is located on a single node on NUMA 
machines, increasing memory pressure on the boot node.

In this patch, I tried to :

- Keep a fast !CONFIG_SMP implementation
- Keep a fast CONFIG_SMP implementation for often used protocols 
(tcp,udp,raw,...)
- Introduce a NUMA efficient implementation

Some helper macros are defined in include/net/sock.h
These macros take into account CONFIG_SMP

If a "struct proto" is declared without using DEFINE_PROTO_INUSE / 
REF_PROTO_INUSE
macros, it will automatically use a default implementation, using a 
dynamically allocated percpu zone.
This default implementation will be NUMA efficient, but might use 32/64 
bytes per possible cpu
because of current alloc_percpu() implementation.
However it still should be better than previous implementation based on 
stats[NR_CPUS] field.

When a "struct proto" is changed to use the new macros, we use a single 
static "int" percpu variable,
lowering the memory and cpu costs, still preserving NUMA efficiency.


Signed-off-by: Eric Dumazet <redacted>

 include/net/sock.h |   63 ++++++++++++++++++++++++++++++++++++++-----
 net/core/sock.c    |   48 ++++++++++++++++++++++++++++++++
 net/ipv4/proc.c    |   19 ++----------
 net/ipv6/proc.c    |   19 ++----------
 4 files changed, 112 insertions(+), 37 deletions(-)