net: add low latency socket poll

Adds an ndo_ll_poll method and the code that supports it.
This method can be used by low latency applications to busy-poll
Ethernet device queues directly from the socket code.
sysctl_net_ll_poll controls how many microseconds to poll.
Default is zero (disabled).
Individual protocol support will be added by subsequent patches.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Tested-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 20 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 73f57a0e1523..4a4181e16c1a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -733,6 +733,10 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
         new->vlan_tci           = old->vlan_tci;
 
         skb_copy_secmark(new, old);
+
+#ifdef CONFIG_NET_LL_RX_POLL
+        new->napi_id    = old->napi_id;
+#endif
 }
 
 /*
diff --git a/net/core/sock.c b/net/core/sock.c
index 88868a9d21da..788c0da5eed1 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -139,6 +139,8 @@
 #include <net/tcp.h>
 #endif
 
+#include <net/ll_poll.h>
+
 static DEFINE_MUTEX(proto_list_mutex);
 static LIST_HEAD(proto_list);
 
@@ -2284,6 +2286,10 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 
         sk->sk_stamp = ktime_set(-1L, 0);
 
+#ifdef CONFIG_NET_LL_RX_POLL
+        sk->sk_napi_id          =       0;
+#endif
+
         /*
          * Before updating sk_refcnt, we must commit prior changes to memory
          * (Documentation/RCU/rculist_nulls.txt for details)
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 741db5fc7806..4b48f39582b0 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -19,6 +19,7 @@
 #include <net/ip.h>
 #include <net/sock.h>
 #include <net/net_ratelimit.h>
+#include <net/ll_poll.h>
 
 static int one = 1;
 
@@ -284,6 +285,15 @@ static struct ctl_table net_core_table[] = {
                 .proc_handler   = flow_limit_table_len_sysctl
         },
 #endif /* CONFIG_NET_FLOW_LIMIT */
+#ifdef CONFIG_NET_LL_RX_POLL
+        {
+                .procname       = "low_latency_poll",
+                .data           = &sysctl_net_ll_poll,
+                .maxlen         = sizeof(unsigned long),
+                .mode           = 0644,
+                .proc_handler   = proc_doulongvec_minmax
+        },
+#endif
 #endif /* CONFIG_NET */
         {
                 .procname       = "netdev_budget",