Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934690AbaGPGWQ (ORCPT ); Wed, 16 Jul 2014 02:22:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14557 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934631AbaGPGWM (ORCPT ); Wed, 16 Jul 2014 02:22:12 -0400 From: Jason Wang To: rusty@rustcorp.com.au, mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Jason Wang , Vlad Yasevich , Eric Dumazet Subject: [PATCH net-next V2 3/3] virtio-net: rx busy polling support Date: Wed, 16 Jul 2014 14:21:47 +0800 Message-Id: <1405491707-22706-4-git-send-email-jasowang@redhat.com> In-Reply-To: <1405491707-22706-1-git-send-email-jasowang@redhat.com> References: <1405491707-22706-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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 */ }; +#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 */ +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) +{ + 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); + + 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); + } + } } 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/