Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751166AbaGTV2r (ORCPT ); Sun, 20 Jul 2014 17:28:47 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38704 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750889AbaGTV2p (ORCPT ); Sun, 20 Jul 2014 17:28:45 -0400 Date: Sun, 20 Jul 2014 23:31:11 +0300 From: "Michael S. Tsirkin" To: Jason Wang Cc: rusty@rustcorp.com.au, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Vlad Yasevich , Eric Dumazet Subject: Re: [PATCH net-next V2 3/3] virtio-net: rx busy polling support Message-ID: <20140720203111.GE2536@redhat.com> References: <1405491707-22706-1-git-send-email-jasowang@redhat.com> <1405491707-22706-4-git-send-email-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1405491707-22706-4-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 16, 2014 at 02:21:47PM +0800, Jason Wang wrote: > Add basic support for rx busy polling. > > Test was done between a kvm guest and an external host. Two hosts were > connected through 40gb mlx4 cards. With both busy_poll and busy_read > are set to 50 in guest, 1 byte netperf tcp_rr shows 116% improvement: > transaction rate was increased from 9151.94 to 19787.37. Pls include data about non polling tests: any effect on cpu utilization there? There could be as we are adding locking. > > Cc: Rusty Russell > Cc: Michael S. Tsirkin > Cc: Vlad Yasevich > Cc: Eric Dumazet > Signed-off-by: Jason Wang > --- > drivers/net/virtio_net.c | 190 ++++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 187 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index e417d93..4830713 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -27,6 +27,7 @@ > #include > #include > #include > +#include > > static int napi_weight = NAPI_POLL_WEIGHT; > module_param(napi_weight, int, 0444); > @@ -94,8 +95,143 @@ struct receive_queue { > > /* Name of this receive queue: input.$index */ > char name[40]; > + > +#ifdef CONFIG_NET_RX_BUSY_POLL > + unsigned int state; > +#define VIRTNET_RQ_STATE_IDLE 0 > +#define VIRTNET_RQ_STATE_NAPI 1 /* NAPI or refill owns this RQ */ > +#define VIRTNET_RQ_STATE_POLL 2 /* poll owns this RQ */ > +#define VIRTNET_RQ_STATE_DISABLED 4 /* RQ is disabled */ > +#define VIRTNET_RQ_OWNED (VIRTNET_RQ_STATE_NAPI | VIRTNET_RQ_STATE_POLL) > +#define VIRTNET_RQ_LOCKED (VIRTNET_RQ_OWNED | VIRTNET_RQ_STATE_DISABLED) > +#define VIRTNET_RQ_STATE_NAPI_YIELD 8 /* NAPI or refill yielded this RQ */ > +#define VIRTNET_RQ_STATE_POLL_YIELD 16 /* poll yielded this RQ */ > + spinlock_t lock; > +#endif /* CONFIG_NET_RX_BUSY_POLL */ do we have to have a new state? no way to reuse the napi state for this? two lock/unlock operations for a poll seems excessive. > }; > > +#ifdef CONFIG_NET_RX_BUSY_POLL > +static inline void virtnet_rq_init_lock(struct receive_queue *rq) > +{ > + > + spin_lock_init(&rq->lock); > + rq->state = VIRTNET_RQ_STATE_IDLE; > +} > + > +/* called from the device poll routine or refill routine to get ownership of a > + * receive queue. > + */ > +static inline bool virtnet_rq_lock_napi_refill(struct receive_queue *rq) > +{ > + int rc = true; > + > + spin_lock(&rq->lock); > + if (rq->state & VIRTNET_RQ_LOCKED) { > + WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI); > + rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD; > + rc = false; > + } else > + /* we don't care if someone yielded */ > + rq->state = VIRTNET_RQ_STATE_NAPI; > + spin_unlock(&rq->lock); > + return rc; > +} > + > +/* returns true is someone tried to get the rq while napi or refill had it */ s/is/if/ > +static inline bool virtnet_rq_unlock_napi_refill(struct receive_queue *rq) > +{ > + int rc = false; > + > + spin_lock(&rq->lock); > + WARN_ON(rq->state & (VIRTNET_RQ_STATE_POLL | > + VIRTNET_RQ_STATE_NAPI_YIELD)); > + > + if (rq->state & VIRTNET_RQ_STATE_POLL_YIELD) > + rc = true; > + /* will reset state to idle, unless RQ is disabled */ > + rq->state &= VIRTNET_RQ_STATE_DISABLED; > + spin_unlock(&rq->lock); > + return rc; > +} > + > +/* called from virtnet_low_latency_recv() */ > +static inline bool virtnet_rq_lock_poll(struct receive_queue *rq) > +{ > + int rc = true; > + > + spin_lock_bh(&rq->lock); > + if ((rq->state & VIRTNET_RQ_LOCKED)) { > + rq->state |= VIRTNET_RQ_STATE_POLL_YIELD; > + rc = false; > + } else > + /* preserve yield marks */ > + rq->state |= VIRTNET_RQ_STATE_POLL; > + spin_unlock_bh(&rq->lock); > + return rc; > +} > + > +/* returns true if someone tried to get the receive queue while it was locked */ > +static inline bool virtnet_rq_unlock_poll(struct receive_queue *rq) > +{ > + int rc = false; > + > + spin_lock_bh(&rq->lock); > + WARN_ON(rq->state & (VIRTNET_RQ_STATE_NAPI)); > + > + if (rq->state & VIRTNET_RQ_STATE_POLL_YIELD) > + rc = true; > + /* will reset state to idle, unless RQ is disabled */ > + rq->state &= VIRTNET_RQ_STATE_DISABLED; > + spin_unlock_bh(&rq->lock); > + return rc; > +} > + > +/* return false if RQ is currently owned */ > +static inline bool virtnet_rq_disable(struct receive_queue *rq) > +{ > + int rc = true; > + > + spin_lock_bh(&rq->lock); > + if (rq->state & VIRTNET_RQ_OWNED) > + rc = false; > + rq->state |= VIRTNET_RQ_STATE_DISABLED; > + spin_unlock_bh(&rq->lock); > + > + return rc; > +} > + > +#else /* CONFIG_NET_RX_BUSY_POLL */ > +static inline void virtnet_rq_init_lock(struct receive_queue *rq) > +{ > +} > + > +static inline bool virtnet_rq_lock_napi_refill(struct receive_queue *rq) > +{ > + return true; > +} > + > +static inline bool virtnet_rq_unlock_napi_refill(struct receive_queue *rq) > +{ > + return false; > +} > + > +static inline bool virtnet_rq_lock_poll(struct receive_queue *rq) > +{ > + return false; > +} > + > +static inline bool virtnet_rq_unlock_poll(struct receive_queue *rq) > +{ > + return false; > +} > + > +static inline bool virtnet_rq_disable(struct receive_queue *rq) > +{ > + return true; > +} > + > +#endif /* CONFIG_NET_RX_BUSY_POLL */ > + > struct virtnet_info { > struct virtio_device *vdev; > struct virtqueue *cvq; > @@ -521,6 +657,8 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len) > skb_shinfo(skb)->gso_segs = 0; > } > > + skb_mark_napi_id(skb, &rq->napi); > + > netif_receive_skb(skb); > return; > > @@ -714,7 +852,12 @@ static void refill_work(struct work_struct *work) > struct receive_queue *rq = &vi->rq[i]; > > napi_disable(&rq->napi); > + if (!virtnet_rq_lock_napi_refill(rq)) { > + virtnet_napi_enable(rq); > + continue; > + } > still_empty = !try_fill_recv(rq, GFP_KERNEL); > + virtnet_rq_unlock_napi_refill(rq); > virtnet_napi_enable(rq); > > /* In theory, this can happen: if we don't get any buffers in > @@ -752,8 +895,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget) > unsigned int r, received = 0; > > again: > + if (!virtnet_rq_lock_napi_refill(rq)) > + return budget; > + > received += virtnet_receive(rq, budget); > > + virtnet_rq_unlock_napi_refill(rq); > + > /* Out of packets? */ > if (received < budget) { > r = virtqueue_enable_cb_prepare(rq->vq); > @@ -770,20 +918,50 @@ again: > return received; > } > > +#ifdef CONFIG_NET_RX_BUSY_POLL > +/* must be called with local_bh_disable()d */ > +static int virtnet_low_latency_recv(struct napi_struct *napi) let's call it busy poll :) > +{ > + struct receive_queue *rq = > + container_of(napi, struct receive_queue, napi); > + struct virtnet_info *vi = rq->vq->vdev->priv; > + int received; > + > + if (!(vi->status & VIRTIO_NET_S_LINK_UP)) > + return LL_FLUSH_FAILED; > + > + if (!virtnet_rq_lock_poll(rq)) > + return LL_FLUSH_BUSY; > + > + received = virtnet_receive(rq, 4); Hmm why 4 exactly? > + > + virtnet_rq_unlock_poll(rq); > + > + return received; > +} > +#endif /* CONFIG_NET_RX_BUSY_POLL */ > + > static void virtnet_napi_enable_all(struct virtnet_info *vi) > { > int i; > > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > + virtnet_rq_init_lock(&vi->rq[i]); > virtnet_napi_enable(&vi->rq[i]); > + } > } > > static void virtnet_napi_disable_all(struct virtnet_info *vi) > { > int i; > > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > napi_disable(&vi->rq[i].napi); > + while (!virtnet_rq_disable(&vi->rq[i])) { > + pr_info("RQ %d locked\n", i); > + usleep_range(1000, 20000); What's going on here, exactly? > + } > + } > } > > static int virtnet_open(struct net_device *dev) > @@ -1372,6 +1550,9 @@ static const struct net_device_ops virtnet_netdev = { > #ifdef CONFIG_NET_POLL_CONTROLLER > .ndo_poll_controller = virtnet_netpoll, > #endif > +#ifdef CONFIG_NET_RX_BUSY_POLL > + .ndo_busy_poll = virtnet_low_latency_recv, > +#endif > }; > > static void virtnet_config_changed_work(struct work_struct *work) > @@ -1577,6 +1758,7 @@ static int virtnet_alloc_queues(struct virtnet_info *vi) > vi->rq[i].pages = NULL; > netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll, > napi_weight); > + napi_hash_add(&vi->rq[i].napi); > > sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg)); > ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT); > @@ -1880,8 +2062,10 @@ static int virtnet_freeze(struct virtio_device *vdev) > > if (netif_running(vi->dev)) { > virtnet_napi_disable_all(vi); > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > + napi_hash_del(&vi->rq[i].napi); > netif_napi_del(&vi->rq[i].napi); > + } > } > > remove_vq_common(vi); > -- > 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/