From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net-next 1/2] net: tap: replay while() loop with % operator in tap_get_queue() Date: Mon, 11 Dec 2017 12:02:46 -0500 (EST) Message-ID: <20171211.120246.1487812563373661375.davem@davemloft.net> References: <1512998801-17852-1-git-send-email-cugyly@163.com> <20171211085811.00c3cbaf@xeon-e3> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: cugyly@163.com, netdev@vger.kernel.org, Linyu.Yuan@alcatel-sbell.com.cn To: stephen@networkplumber.org Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:36868 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751512AbdLKRCr (ORCPT ); Mon, 11 Dec 2017 12:02:47 -0500 In-Reply-To: <20171211085811.00c3cbaf@xeon-e3> Sender: netdev-owner@vger.kernel.org List-ID: From: Stephen Hemminger Date: Mon, 11 Dec 2017 08:58:11 -0800 > On Mon, 11 Dec 2017 21:26:41 +0800 > yuan linyu wrote: > >> From: yuan linyu >> >> Signed-off-by: yuan linyu >> --- >> drivers/net/tap.c | 6 +----- >> 1 file changed, 1 insertion(+), 5 deletions(-) >> >> diff --git a/drivers/net/tap.c b/drivers/net/tap.c >> index 0a886fda..78900a0 100644 >> --- a/drivers/net/tap.c >> +++ b/drivers/net/tap.c >> @@ -275,11 +275,7 @@ static struct tap_queue *tap_get_queue(struct tap_dev *tap, >> >> if (likely(skb_rx_queue_recorded(skb))) { >> rxq = skb_get_rx_queue(skb); >> - >> - while (unlikely(rxq >= numvtaps)) >> - rxq -= numvtaps; >> - >> - queue = rcu_dereference(tap->taps[rxq]); >> + queue = rcu_dereference(tap->taps[rxq % numvtaps]); >> goto out; >> } >> > > Modulus is slower than the loop. Agreed, the loop is there intentionally. We do this in other areas of the kernel as well.