net: add cpu_relax to busy poll loop
Add a cpu_relaxt to sk_busy_loop.
Julie Cummings reported performance issues when hyperthreading is on.
Arjan van de Ven observed that we should have a cpu_relax() in the
busy poll loop.
Reported-by: Julie Cummings <julie.a.cummings@intel.com>
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 8a358a2..829627d 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -123,6 +123,7 @@
/* local bh are disabled so it is ok to use _BH */
NET_ADD_STATS_BH(sock_net(sk),
LINUX_MIB_BUSYPOLLRXPACKETS, rc);
+ cpu_relax();
} while (!nonblock && skb_queue_empty(&sk->sk_receive_queue) &&
!need_resched() && !busy_loop_timeout(end_time));