Michael S. Tsirkin
2014-Oct-15 14:32 UTC
[PATCH RFC v2 1/3] virtio_net: enable tx interrupt
On newer hosts that support delayed tx interrupts,
we probably don't have much to gain from orphaning
packets early.
Based on patch by Jason Wang.
Note: this might degrade performance for
hosts without event idx support.
Should be addressed by the next patch.
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---
drivers/net/virtio_net.c | 137 ++++++++++++++++++++++++++++++++---------------
1 file changed, 94 insertions(+), 43 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 13d0a8b..a9bf178 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -72,6 +72,8 @@ struct send_queue {
/* Name of the send queue: output.$index */
char name[40];
+
+ struct napi_struct napi;
};
/* Internal representation of a receive virtqueue */
@@ -217,15 +219,37 @@ static struct page *get_a_page(struct receive_queue *rq,
gfp_t gfp_mask)
return p;
}
+static unsigned int free_old_xmit_skbs(struct send_queue *sq, int budget)
+{
+ struct sk_buff *skb;
+ unsigned int len;
+ struct virtnet_info *vi = sq->vq->vdev->priv;
+ struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
+ unsigned int packets = 0;
+
+ while (packets < budget &&
+ (skb = virtqueue_get_buf(sq->vq, &len)) != NULL) {
+ pr_debug("Sent skb %p\n", skb);
+
+ u64_stats_update_begin(&stats->tx_syncp);
+ stats->tx_bytes += skb->len;
+ stats->tx_packets++;
+ u64_stats_update_end(&stats->tx_syncp);
+
+ dev_kfree_skb_any(skb);
+ packets++;
+ }
+
+ return packets;
+}
+
static void skb_xmit_done(struct virtqueue *vq)
{
struct virtnet_info *vi = vq->vdev->priv;
+ struct send_queue *sq = &vi->sq[vq2txq(vq)];
- /* Suppress further interrupts. */
- virtqueue_disable_cb(vq);
-
- /* We were probably waiting for more output buffers. */
- netif_wake_subqueue(vi->dev, vq2txq(vq));
+ if (napi_schedule_prep(&sq->napi))
+ __napi_schedule(&sq->napi);
}
static unsigned int mergeable_ctx_to_buf_truesize(unsigned long mrg_ctx)
@@ -774,6 +798,37 @@ again:
return received;
}
+static int virtnet_poll_tx(struct napi_struct *napi, int budget)
+{
+ struct send_queue *sq + container_of(napi, struct send_queue, napi);
+ struct virtnet_info *vi = sq->vq->vdev->priv;
+ struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, vq2txq(sq->vq));
+ unsigned int sent = 0;
+ bool enable_done;
+
+again:
+ __netif_tx_lock(txq, smp_processor_id());
+ virtqueue_disable_cb(sq->vq);
+ sent += free_old_xmit_skbs(sq, budget - sent);
+
+ if (sent < budget) {
+ enable_done = virtqueue_enable_cb_delayed(sq->vq);
+ napi_complete(napi);
+ __netif_tx_unlock(txq);
+ if (unlikely(enable_done) && napi_schedule_prep(napi)) {
+ virtqueue_disable_cb(sq->vq);
+ __napi_schedule(napi);
+ goto again;
+ }
+ } else {
+ __netif_tx_unlock(txq);
+ }
+
+ netif_wake_subqueue(vi->dev, vq2txq(sq->vq));
+ return sent;
+}
+
#ifdef CONFIG_NET_RX_BUSY_POLL
/* must be called with local_bh_disable()d */
static int virtnet_busy_poll(struct napi_struct *napi)
@@ -822,30 +877,12 @@ static int virtnet_open(struct net_device *dev)
if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
schedule_delayed_work(&vi->refill, 0);
virtnet_napi_enable(&vi->rq[i]);
+ napi_enable(&vi->sq[i].napi);
}
return 0;
}
-static void free_old_xmit_skbs(struct send_queue *sq)
-{
- struct sk_buff *skb;
- unsigned int len;
- struct virtnet_info *vi = sq->vq->vdev->priv;
- struct virtnet_stats *stats = this_cpu_ptr(vi->stats);
-
- while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) {
- pr_debug("Sent skb %p\n", skb);
-
- u64_stats_update_begin(&stats->tx_syncp);
- stats->tx_bytes += skb->len;
- stats->tx_packets++;
- u64_stats_update_end(&stats->tx_syncp);
-
- dev_kfree_skb_any(skb);
- }
-}
-
static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
{
struct skb_vnet_hdr *hdr;
@@ -911,7 +948,9 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff
*skb)
sg_set_buf(sq->sg, hdr, hdr_len);
num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1;
}
- return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC);
+
+ return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb,
+ GFP_ATOMIC);
}
static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
@@ -919,12 +958,16 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct
net_device *dev)
struct virtnet_info *vi = netdev_priv(dev);
int qnum = skb_get_queue_mapping(skb);
struct send_queue *sq = &vi->sq[qnum];
- int err;
+ int err, qsize = virtqueue_get_vring_size(sq->vq);
struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum);
bool kick = !skb->xmit_more;
+ bool stopped;
+
+ virtqueue_disable_cb(sq->vq);
- /* Free up any pending old buffers before queueing new ones. */
- free_old_xmit_skbs(sq);
+ /* We are going to push one skb.
+ * Try to pop one off to free space for it. */
+ free_old_xmit_skbs(sq, 1);
/* Try to transmit */
err = xmit_skb(sq, skb);
@@ -940,27 +983,25 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct
net_device *dev)
return NETDEV_TX_OK;
}
- /* Don't wait up for transmitted skbs to be freed. */
- skb_orphan(skb);
- nf_reset(skb);
-
/* Apparently nice girls don't return TX_BUSY; stop the queue
* before it gets out of hand. Naturally, this wastes entries. */
if (sq->vq->num_free < 2+MAX_SKB_FRAGS) {
netif_stop_subqueue(dev, qnum);
- if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
- /* More just got used, free them then recheck. */
- free_old_xmit_skbs(sq);
- if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) {
- netif_start_subqueue(dev, qnum);
- virtqueue_disable_cb(sq->vq);
- }
- }
+ stopped = true;
+ } else {
+ stopped = false;
}
if (kick || netif_xmit_stopped(txq))
virtqueue_kick(sq->vq);
+ if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) {
+ /* More just got used, free them then recheck. */
+ free_old_xmit_skbs(sq, qsize);
+ if (stopped && sq->vq->num_free >= 2+MAX_SKB_FRAGS)
+ netif_start_subqueue(dev, qnum);
+ }
+
return NETDEV_TX_OK;
}
@@ -1137,8 +1178,10 @@ static int virtnet_close(struct net_device *dev)
/* Make sure refill_work doesn't re-enable napi! */
cancel_delayed_work_sync(&vi->refill);
- for (i = 0; i < vi->max_queue_pairs; i++)
+ for (i = 0; i < vi->max_queue_pairs; i++) {
napi_disable(&vi->rq[i].napi);
+ napi_disable(&vi->sq[i].napi);
+ }
return 0;
}
@@ -1457,8 +1500,10 @@ static void virtnet_free_queues(struct virtnet_info *vi)
{
int i;
- for (i = 0; i < vi->max_queue_pairs; i++)
+ for (i = 0; i < vi->max_queue_pairs; i++) {
netif_napi_del(&vi->rq[i].napi);
+ netif_napi_del(&vi->sq[i].napi);
+ }
kfree(vi->rq);
kfree(vi->sq);
@@ -1612,6 +1657,8 @@ static int virtnet_alloc_queues(struct virtnet_info *vi)
netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll,
napi_weight);
napi_hash_add(&vi->rq[i].napi);
+ netif_napi_add(vi->dev, &vi->sq[i].napi, virtnet_poll_tx,
+ napi_weight);
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);
@@ -1916,8 +1963,10 @@ static int virtnet_freeze(struct virtio_device *vdev)
if (netif_running(vi->dev)) {
for (i = 0; i < vi->max_queue_pairs; i++) {
napi_disable(&vi->rq[i].napi);
+ napi_disable(&vi->sq[i].napi);
napi_hash_del(&vi->rq[i].napi);
netif_napi_del(&vi->rq[i].napi);
+ netif_napi_del(&vi->sq[i].napi);
}
}
@@ -1942,8 +1991,10 @@ static int virtnet_restore(struct virtio_device *vdev)
if (!try_fill_recv(&vi->rq[i], GFP_KERNEL))
schedule_delayed_work(&vi->refill, 0);
- for (i = 0; i < vi->max_queue_pairs; i++)
+ for (i = 0; i < vi->max_queue_pairs; i++) {
virtnet_napi_enable(&vi->rq[i]);
+ napi_enable(&vi->sq[i].napi);
+ }
}
netif_device_attach(vi->dev);
--
MST
On 10/15/2014 10:32 PM, Michael S. Tsirkin wrote:> On newer hosts that support delayed tx interrupts, > we probably don't have much to gain from orphaning > packets early. > > Based on patch by Jason Wang. > > Note: this might degrade performance for > hosts without event idx support. > Should be addressed by the next patch. > > Signed-off-by: Michael S. Tsirkin <mst at redhat.com> > --- > drivers/net/virtio_net.c | 137 ++++++++++++++++++++++++++++++++--------------- > 1 file changed, 94 insertions(+), 43 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 13d0a8b..a9bf178 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -72,6 +72,8 @@ struct send_queue { > > /* Name of the send queue: output.$index */ > char name[40]; > + > + struct napi_struct napi; > }; > > /* Internal representation of a receive virtqueue */ > @@ -217,15 +219,37 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) > return p; > } > > +static unsigned int free_old_xmit_skbs(struct send_queue *sq, int budget) > +{ > + struct sk_buff *skb; > + unsigned int len; > + struct virtnet_info *vi = sq->vq->vdev->priv; > + struct virtnet_stats *stats = this_cpu_ptr(vi->stats); > + unsigned int packets = 0; > + > + while (packets < budget && > + (skb = virtqueue_get_buf(sq->vq, &len)) != NULL) { > + pr_debug("Sent skb %p\n", skb); > + > + u64_stats_update_begin(&stats->tx_syncp); > + stats->tx_bytes += skb->len; > + stats->tx_packets++; > + u64_stats_update_end(&stats->tx_syncp); > + > + dev_kfree_skb_any(skb); > + packets++; > + } > + > + return packets; > +} > + > static void skb_xmit_done(struct virtqueue *vq) > { > struct virtnet_info *vi = vq->vdev->priv; > + struct send_queue *sq = &vi->sq[vq2txq(vq)]; > > - /* Suppress further interrupts. */ > - virtqueue_disable_cb(vq); > - > - /* We were probably waiting for more output buffers. */ > - netif_wake_subqueue(vi->dev, vq2txq(vq)); > + if (napi_schedule_prep(&sq->napi)) > + __napi_schedule(&sq->napi); > } > > static unsigned int mergeable_ctx_to_buf_truesize(unsigned long mrg_ctx) > @@ -774,6 +798,37 @@ again: > return received; > } > > +static int virtnet_poll_tx(struct napi_struct *napi, int budget) > +{ > + struct send_queue *sq > + container_of(napi, struct send_queue, napi); > + struct virtnet_info *vi = sq->vq->vdev->priv; > + struct netdev_queue *txq = netdev_get_tx_queue(vi->dev, vq2txq(sq->vq)); > + unsigned int sent = 0; > + bool enable_done; > + > +again: > + __netif_tx_lock(txq, smp_processor_id()); > + virtqueue_disable_cb(sq->vq); > + sent += free_old_xmit_skbs(sq, budget - sent); > + > + if (sent < budget) { > + enable_done = virtqueue_enable_cb_delayed(sq->vq); > + napi_complete(napi); > + __netif_tx_unlock(txq); > + if (unlikely(enable_done) && napi_schedule_prep(napi)) {I think you mean unlikely(!enable_done) here?> + virtqueue_disable_cb(sq->vq); > + __napi_schedule(napi); > + goto again; > + } > + } else { > + __netif_tx_unlock(txq); > + } > + > + netif_wake_subqueue(vi->dev, vq2txq(sq->vq)); > + return sent; > +} > + > #ifdef CONFIG_NET_RX_BUSY_POLL > /* must be called with local_bh_disable()d */ > static int virtnet_busy_poll(struct napi_struct *napi) > @@ -822,30 +877,12 @@ static int virtnet_open(struct net_device *dev) > if (!try_fill_recv(&vi->rq[i], GFP_KERNEL)) > schedule_delayed_work(&vi->refill, 0); > virtnet_napi_enable(&vi->rq[i]); > + napi_enable(&vi->sq[i].napi); > } > > return 0; > } > > -static void free_old_xmit_skbs(struct send_queue *sq) > -{ > - struct sk_buff *skb; > - unsigned int len; > - struct virtnet_info *vi = sq->vq->vdev->priv; > - struct virtnet_stats *stats = this_cpu_ptr(vi->stats); > - > - while ((skb = virtqueue_get_buf(sq->vq, &len)) != NULL) { > - pr_debug("Sent skb %p\n", skb); > - > - u64_stats_update_begin(&stats->tx_syncp); > - stats->tx_bytes += skb->len; > - stats->tx_packets++; > - u64_stats_update_end(&stats->tx_syncp); > - > - dev_kfree_skb_any(skb); > - } > -} > - > static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) > { > struct skb_vnet_hdr *hdr; > @@ -911,7 +948,9 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb) > sg_set_buf(sq->sg, hdr, hdr_len); > num_sg = skb_to_sgvec(skb, sq->sg + 1, 0, skb->len) + 1; > } > - return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, GFP_ATOMIC); > + > + return virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, skb, > + GFP_ATOMIC); > } > > static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > @@ -919,12 +958,16 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > struct virtnet_info *vi = netdev_priv(dev); > int qnum = skb_get_queue_mapping(skb); > struct send_queue *sq = &vi->sq[qnum]; > - int err; > + int err, qsize = virtqueue_get_vring_size(sq->vq); > struct netdev_queue *txq = netdev_get_tx_queue(dev, qnum); > bool kick = !skb->xmit_more; > + bool stopped; > + > + virtqueue_disable_cb(sq->vq); > > - /* Free up any pending old buffers before queueing new ones. */ > - free_old_xmit_skbs(sq); > + /* We are going to push one skb. > + * Try to pop one off to free space for it. */ > + free_old_xmit_skbs(sq, 1);Looks like qsize instead of 1 is better? The more skbs freed in ndo_start_xmit() the less chance tx napi will be scheduled.> > /* Try to transmit */ > err = xmit_skb(sq, skb); > @@ -940,27 +983,25 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > return NETDEV_TX_OK; > } > > - /* Don't wait up for transmitted skbs to be freed. */ > - skb_orphan(skb); > - nf_reset(skb); > - > /* Apparently nice girls don't return TX_BUSY; stop the queue > * before it gets out of hand. Naturally, this wastes entries. */ > if (sq->vq->num_free < 2+MAX_SKB_FRAGS) { > netif_stop_subqueue(dev, qnum); > - if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { > - /* More just got used, free them then recheck. */ > - free_old_xmit_skbs(sq); > - if (sq->vq->num_free >= 2+MAX_SKB_FRAGS) { > - netif_start_subqueue(dev, qnum); > - virtqueue_disable_cb(sq->vq); > - } > - } > + stopped = true; > + } else { > + stopped = false; > } > > if (kick || netif_xmit_stopped(txq)) > virtqueue_kick(sq->vq);Looks like we'd better move this in the end in case the queue could be restarted by following lines?> > + if (unlikely(!virtqueue_enable_cb_delayed(sq->vq))) { > + /* More just got used, free them then recheck. */ > + free_old_xmit_skbs(sq, qsize); > + if (stopped && sq->vq->num_free >= 2+MAX_SKB_FRAGS) > + netif_start_subqueue(dev, qnum);Why drop virtqueue_disable_cb() here?> + } > + > return NETDEV_TX_OK; > } > > @@ -1137,8 +1178,10 @@ static int virtnet_close(struct net_device *dev) > /* Make sure refill_work doesn't re-enable napi! */ > cancel_delayed_work_sync(&vi->refill); > > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > napi_disable(&vi->rq[i].napi); > + napi_disable(&vi->sq[i].napi); > + } > > return 0; > } > @@ -1457,8 +1500,10 @@ static void virtnet_free_queues(struct virtnet_info *vi) > { > int i; > > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > netif_napi_del(&vi->rq[i].napi); > + netif_napi_del(&vi->sq[i].napi); > + } > > kfree(vi->rq); > kfree(vi->sq); > @@ -1612,6 +1657,8 @@ static int virtnet_alloc_queues(struct virtnet_info *vi) > netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll, > napi_weight); > napi_hash_add(&vi->rq[i].napi); > + netif_napi_add(vi->dev, &vi->sq[i].napi, virtnet_poll_tx, > + napi_weight); > > 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); > @@ -1916,8 +1963,10 @@ static int virtnet_freeze(struct virtio_device *vdev) > if (netif_running(vi->dev)) { > for (i = 0; i < vi->max_queue_pairs; i++) { > napi_disable(&vi->rq[i].napi); > + napi_disable(&vi->sq[i].napi); > napi_hash_del(&vi->rq[i].napi); > netif_napi_del(&vi->rq[i].napi); > + netif_napi_del(&vi->sq[i].napi); > } > } > > @@ -1942,8 +1991,10 @@ static int virtnet_restore(struct virtio_device *vdev) > if (!try_fill_recv(&vi->rq[i], GFP_KERNEL)) > schedule_delayed_work(&vi->refill, 0); > > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > virtnet_napi_enable(&vi->rq[i]); > + napi_enable(&vi->sq[i].napi); > + } > } > > netif_device_attach(vi->dev);