From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eliezer Tamir Subject: [PATCH net] net: add cpu_relax to busy poll loop Date: Sun, 25 Aug 2013 10:23:46 +0300 Message-ID: <20130825072346.31655.84970.stgit@ladj378.jer.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Eliezer Tamir To: David Miller Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 Signed-off-by: Eliezer Tamir --- include/net/busy_poll.h | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) 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 @@ static inline bool sk_busy_loop(struct sock *sk, int nonblock) /* 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));