2013-08-25 07:23:50

by Eliezer Tamir

Subject: [PATCH net] 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 <[email protected]>
Signed-off-by: Eliezer Tamir <[email protected]>
---

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));

2013-08-28 21:46:25

by David Miller

Subject: Re: [PATCH net] net: add cpu_relax to busy poll loop

From: Eliezer Tamir <[email protected]>
Date: Sun, 25 Aug 2013 10:23:46 +0300

> 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 <[email protected]>
> Signed-off-by: Eliezer Tamir <[email protected]>

Applied, thank you.