net: busy-poll: return busypolling status to drivers

NAPI drivers use napi_complete_done() or napi_complete() when
they drained RX ring and right before re-enabling device interrupts.

In busy polling, we can avoid interrupts being delivered since
we are polling RX ring in a controlled loop.

Drivers can chose to use napi_complete_done() return value
to reduce interrupts overhead while busy polling is active.

This is optional, legacy drivers should work fine even
if not updated.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Adam Belay <abelay@google.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Cc: Yuval Mintz <Yuval.Mintz@cavium.com>
Cc: Ariel Elior <ariel.elior@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 4 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 369dcc8efc01..edba9efeb2e9 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4898,7 +4898,7 @@ void __napi_schedule_irqoff(struct napi_struct *n)
 }
 EXPORT_SYMBOL(__napi_schedule_irqoff);
 
-void __napi_complete(struct napi_struct *n)
+bool __napi_complete(struct napi_struct *n)
 {
         BUG_ON(!test_bit(NAPI_STATE_SCHED, &n->state));
 
@@ -4906,15 +4906,16 @@ void __napi_complete(struct napi_struct *n)
          * napi_complete_done().
          */
         if (unlikely(test_bit(NAPI_STATE_IN_BUSY_POLL, &n->state)))
-                return;
+                return false;
 
         list_del_init(&n->poll_list);
         smp_mb__before_atomic();
         clear_bit(NAPI_STATE_SCHED, &n->state);
+        return true;
 }
 EXPORT_SYMBOL(__napi_complete);
 
-void napi_complete_done(struct napi_struct *n, int work_done)
+bool napi_complete_done(struct napi_struct *n, int work_done)
 {
         unsigned long flags;
 
@@ -4926,7 +4927,7 @@ void napi_complete_done(struct napi_struct *n, int work_done)
          */
         if (unlikely(n->state & (NAPIF_STATE_NPSVC |
                                  NAPIF_STATE_IN_BUSY_POLL)))
-                return;
+                return false;
 
         if (n->gro_list) {
                 unsigned long timeout = 0;
@@ -4948,6 +4949,7 @@ void napi_complete_done(struct napi_struct *n, int work_done)
                 __napi_complete(n);
                 local_irq_restore(flags);
         }
+        return true;
 }
 EXPORT_SYMBOL(napi_complete_done);