From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [Patch net-next v3 2/3] net_sched: plug in qdisc ops change_tx_queue_len Date: Fri, 26 Jan 2018 16:16:58 +0200 Message-ID: <20180126161509-mutt-send-email-mst@kernel.org> References: <20180126022624.20442-1-xiyou.wangcong@gmail.com> <20180126022624.20442-3-xiyou.wangcong@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, john.fastabend@gmail.com To: Cong Wang Return-path: Received: from mx1.redhat.com ([209.132.183.28]:40362 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751324AbeAZOQ7 (ORCPT ); Fri, 26 Jan 2018 09:16:59 -0500 Content-Disposition: inline In-Reply-To: <20180126022624.20442-3-xiyou.wangcong@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Jan 25, 2018 at 06:26:23PM -0800, Cong Wang wrote: > Introduce a new qdisc ops ->change_tx_queue_len() so that > each qdisc could decide how to implement this if it wants. > Previously we simply read dev->tx_queue_len, after pfifo_fast > switches to skb array, we need this API to resize the skb array > when we change dev->tx_queue_len. > > To avoid handling race conditions with TX BH, we need to > deactivate all TX queues before change the value and bring them > back after we are done, this also makes implementation easier. > > Cc: John Fastabend > Signed-off-by: Cong Wang > --- > include/net/sch_generic.h | 2 ++ > net/core/dev.c | 1 + > net/sched/sch_generic.c | 33 +++++++++++++++++++++++++++++++++ > 3 files changed, 36 insertions(+) > > diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h > index eac43e8ca96d..e2ab13687fb9 100644 > --- a/include/net/sch_generic.h > +++ b/include/net/sch_generic.h > @@ -200,6 +200,7 @@ struct Qdisc_ops { > struct nlattr *arg, > struct netlink_ext_ack *extack); > void (*attach)(struct Qdisc *sch); > + int (*change_tx_queue_len)(struct Qdisc *, unsigned int); > > int (*dump)(struct Qdisc *, struct sk_buff *); > int (*dump_stats)(struct Qdisc *, struct gnet_dump *); > @@ -489,6 +490,7 @@ void qdisc_class_hash_remove(struct Qdisc_class_hash *, > void qdisc_class_hash_grow(struct Qdisc *, struct Qdisc_class_hash *); > void qdisc_class_hash_destroy(struct Qdisc_class_hash *); > > +int dev_qdisc_change_tx_queue_len(struct net_device *dev); > void dev_init_scheduler(struct net_device *dev); > void dev_shutdown(struct net_device *dev); > void dev_activate(struct net_device *dev); > diff --git a/net/core/dev.c b/net/core/dev.c > index e0b0c2784070..c8443cfaa17a 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -7070,6 +7070,7 @@ int dev_change_tx_queue_len(struct net_device *dev, unsigned long new_len) > dev->tx_queue_len = orig_len; > return res; > } > + return dev_qdisc_change_tx_queue_len(dev); > } > > return 0; > diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c > index 1816bde47256..08f9fa27e06e 100644 > --- a/net/sched/sch_generic.c > +++ b/net/sched/sch_generic.c > @@ -1178,6 +1178,39 @@ void dev_deactivate(struct net_device *dev) > } > EXPORT_SYMBOL(dev_deactivate); > > +static int qdisc_change_tx_queue_len(struct net_device *dev, > + struct netdev_queue *dev_queue) > +{ > + struct Qdisc *qdisc = dev_queue->qdisc_sleeping; > + const struct Qdisc_ops *ops = qdisc->ops; > + > + if (ops->change_tx_queue_len) > + return ops->change_tx_queue_len(qdisc, dev->tx_queue_len); > + return 0; > +} > + > +int dev_qdisc_change_tx_queue_len(struct net_device *dev) > +{ > + bool up = dev->flags & IFF_UP; > + unsigned int i; > + int ret = 0; > + > + if (up) > + dev_deactivate(dev); This drops all packets in the queue. I don't think tweaking the queue length did this previously - did it? If not this change might surprise some people. > + > + for (i = 0; i < dev->num_tx_queues; i++) { > + ret = qdisc_change_tx_queue_len(dev, &dev->_tx[i]); > + > + /* TODO: revert changes on a partial failure */ > + if (ret) > + break; > + } > + > + if (up) > + dev_activate(dev); > + return ret; > +} > + > static void dev_init_scheduler_queue(struct net_device *dev, > struct netdev_queue *dev_queue, > void *_qdisc) > -- > 2.13.0