From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesper Dangaard Brouer Subject: Re: [RFC PATCH v2 08/10] net: sched: pfifo_fast use alf_queue Date: Fri, 15 Jul 2016 12:09:36 +0200 Message-ID: <20160715120936.0b339b2a@redhat.com> References: <20160714061852.8270.66271.stgit@john-Precision-Tower-5810> <20160714062312.8270.65942.stgit@john-Precision-Tower-5810> <20160714171148.3bb7b47b@redhat.com> <578829C7.8060604@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: fw@strlen.de, jhs@mojatatu.com, alexei.starovoitov@gmail.com, eric.dumazet@gmail.com, netdev@vger.kernel.org, brouer@redhat.com, "Michael S. Tsirkin" To: John Fastabend Return-path: Received: from mx1.redhat.com ([209.132.183.28]:34922 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753094AbcGOKJl (ORCPT ); Fri, 15 Jul 2016 06:09:41 -0400 In-Reply-To: <578829C7.8060604@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 14 Jul 2016 17:09:43 -0700 John Fastabend wrote: > >> static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc, > >> struct sk_buff **to_free) > >> { > >> - if (skb_queue_len(&qdisc->q) < qdisc_dev(qdisc)->tx_queue_len) { > >> - int band = prio2band[skb->priority & TC_PRIO_MAX]; > >> - struct pfifo_fast_priv *priv = qdisc_priv(qdisc); > >> - struct sk_buff_head *list = band2list(priv, band); > >> - > >> - priv->bitmap |= (1 << band); > >> - qdisc->q.qlen++; > >> - return __qdisc_enqueue_tail(skb, qdisc, list); > >> - } > >> + int band = prio2band[skb->priority & TC_PRIO_MAX]; > >> + struct pfifo_fast_priv *priv = qdisc_priv(qdisc); > >> + struct skb_array *q = band2list(priv, band); > >> + int err; > >> > >> - return qdisc_drop(skb, qdisc, to_free); > >> + err = skb_array_produce_bh(q, skb); > > > > Do you need the _bh variant here? (Doesn't the qdisc run with BH disabled?) > > > > > > Yep its inside rcu_read_lock_bh(). The call rcu_read_lock_bh() already disabled BH (local_bh_disable()). Thus, you can use the normal variants of skb_array_produce(), it is (approx 20 cycles) faster than the _bh variant... -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer