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Date: Wed, 16 Jul 2014 14:21:47 +0800
From: Jason Wang <jasowang@...hat.com>
To: rusty@...tcorp.com.au, mst@...hat.com,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Jason Wang <jasowang@...hat.com>,
Vlad Yasevich <vyasevic@...hat.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next V2 3/3] virtio-net: rx busy polling support
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 <rusty@...tcorp.com.au>
Cc: Michael S. Tsirkin <mst@...hat.com>
Cc: Vlad Yasevich <vyasevic@...hat.com>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
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 <linux/slab.h>
#include <linux/cpu.h>
#include <linux/average.h>
+#include <net/busy_poll.h>
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
--
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