[NET]: Define 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 <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 15 deletions

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index be526ad..8631ed7 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -32,27 +32,16 @@
 
 static struct proc_dir_entry *proc_net_devsnmp6;
 
-static int fold_prot_inuse(struct proto *proto)
-{
-	int res = 0;
-	int cpu;
-
-	for_each_possible_cpu(cpu)
-		res += proto->stats[cpu].inuse;
-
-	return res;
-}
-
 static int sockstat6_seq_show(struct seq_file *seq, void *v)
 {
 	seq_printf(seq, "TCP6: inuse %d\n",
-		       fold_prot_inuse(&tcpv6_prot));
+		       sock_prot_inuse(&tcpv6_prot));
 	seq_printf(seq, "UDP6: inuse %d\n",
-		       fold_prot_inuse(&udpv6_prot));
+		       sock_prot_inuse(&udpv6_prot));
 	seq_printf(seq, "UDPLITE6: inuse %d\n",
-			fold_prot_inuse(&udplitev6_prot));
+			sock_prot_inuse(&udplitev6_prot));
 	seq_printf(seq, "RAW6: inuse %d\n",
-		       fold_prot_inuse(&rawv6_prot));
+		       sock_prot_inuse(&rawv6_prot));
 	seq_printf(seq, "FRAG6: inuse %d memory %d\n",
 		       ip6_frag_nqueues(), ip6_frag_mem());
 	return 0;