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Message-ID: <5429EFBB.2090909@oracle.com>
Date: Mon, 29 Sep 2014 19:48:11 -0400
From: David L Stevens <david.stevens@...cle.com>
To: David Miller <davem@...emloft.net>
CC: netdev@...r.kernel.org,
Sowmini Varadhan <sowmini.varadhan@...cle.com>,
Raghuram Kothahota <raghuram.kothakota@...cle.com>
Subject: [PATCHv9 net-next 2/4] sunvnet: make transmit path zero-copy in the
kernel
This patch removes pre-allocated transmit buffers and instead directly maps
pending packets on demand. This saves O(n^2) maximum-sized transmit buffers,
for n hosts on a vswitch, as well as a copy to those buffers.
Single-stream TCP throughput linux-solaris dropped ~5% for 1500-byte MTU,
but linux-linux at 1500-bytes increased ~20%.
Signed-off-by: David L Stevens <david.stevens@...cle.com>
---
drivers/net/ethernet/sun/sunvnet.c | 218 ++++++++++++++++++++++++++++-------
drivers/net/ethernet/sun/sunvnet.h | 9 ++-
2 files changed, 182 insertions(+), 45 deletions(-)
diff --git a/drivers/net/ethernet/sun/sunvnet.c b/drivers/net/ethernet/sun/sunvnet.c
index b1abcad..8f5f4e3 100644
--- a/drivers/net/ethernet/sun/sunvnet.c
+++ b/drivers/net/ethernet/sun/sunvnet.c
@@ -780,6 +780,117 @@ struct vnet_port *tx_port_find(struct vnet *vp, struct sk_buff *skb)
return ret;
}
+static struct sk_buff *vnet_clean_tx_ring(struct vnet_port *port,
+ unsigned *pending)
+{
+ struct vio_dring_state *dr = &port->vio.drings[VIO_DRIVER_TX_RING];
+ struct sk_buff *skb = NULL;
+ int i, txi;
+
+ *pending = 0;
+
+ txi = dr->prod-1;
+ if (txi < 0)
+ txi = VNET_TX_RING_SIZE-1;
+
+ for (i = 0; i < VNET_TX_RING_SIZE; ++i) {
+ struct vio_net_desc *d;
+
+ d = vio_dring_entry(dr, txi);
+
+ if (d->hdr.state == VIO_DESC_DONE) {
+ if (port->tx_bufs[txi].skb) {
+ BUG_ON(port->tx_bufs[txi].skb->next);
+
+ port->tx_bufs[txi].skb->next = skb;
+ skb = port->tx_bufs[txi].skb;
+ port->tx_bufs[txi].skb = NULL;
+
+ ldc_unmap(port->vio.lp,
+ port->tx_bufs[txi].cookies,
+ port->tx_bufs[txi].ncookies);
+ }
+ d->hdr.state = VIO_DESC_FREE;
+ } else if (d->hdr.state == VIO_DESC_READY) {
+ (*pending)++;
+ } else if (d->hdr.state == VIO_DESC_FREE) {
+ break;
+ }
+ --txi;
+ if (txi < 0)
+ txi = VNET_TX_RING_SIZE-1;
+ }
+ return skb;
+}
+
+static inline void vnet_free_skbs(struct sk_buff *skb)
+{
+ struct sk_buff *next;
+
+ while (skb) {
+ next = skb->next;
+ skb->next = NULL;
+ dev_kfree_skb(skb);
+ skb = next;
+ }
+}
+
+static void vnet_clean_timer_expire(unsigned long port0)
+{
+ struct vnet_port *port = (struct vnet_port *)port0;
+ struct sk_buff *freeskbs;
+ unsigned pending;
+ unsigned long flags;
+
+ spin_lock_irqsave(&port->vio.lock, flags);
+ freeskbs = vnet_clean_tx_ring(port, &pending);
+ spin_unlock_irqrestore(&port->vio.lock, flags);
+
+ vnet_free_skbs(freeskbs);
+
+ if (pending)
+ (void)mod_timer(&port->clean_timer,
+ jiffies + VNET_CLEAN_TIMEOUT);
+ else
+ del_timer(&port->clean_timer);
+}
+
+static inline struct sk_buff *vnet_skb_shape(struct sk_buff *skb, void **pstart,
+ int *plen)
+{
+ struct sk_buff *nskb;
+ int len, pad;
+
+ len = skb->len;
+ pad = 0;
+ if (len < ETH_ZLEN) {
+ pad += ETH_ZLEN - skb->len;
+ len += pad;
+ }
+ len += VNET_PACKET_SKIP;
+ pad += 8 - (len & 7);
+ len += 8 - (len & 7);
+
+ if (((unsigned long)skb->data & 7) != VNET_PACKET_SKIP ||
+ skb_tailroom(skb) < pad ||
+ skb_headroom(skb) < VNET_PACKET_SKIP) {
+ nskb = alloc_and_align_skb(skb->dev, skb->len);
+ skb_reserve(nskb, VNET_PACKET_SKIP);
+ if (skb_copy_bits(skb, 0, nskb->data, skb->len)) {
+ dev_kfree_skb(nskb);
+ dev_kfree_skb(skb);
+ return NULL;
+ }
+ (void)skb_put(nskb, skb->len);
+ dev_kfree_skb(skb);
+ skb = nskb;
+ }
+
+ *pstart = skb->data - VNET_PACKET_SKIP;
+ *plen = len;
+ return skb;
+}
+
static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct vnet *vp = netdev_priv(dev);
@@ -788,12 +899,20 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
struct vio_net_desc *d;
unsigned long flags;
unsigned int len;
- void *tx_buf;
- int i, err;
+ struct sk_buff *freeskbs = NULL;
+ int i, err, txi;
+ void *start = NULL;
+ int nlen = 0;
+ unsigned pending = 0;
if (unlikely(!port))
goto out_dropped;
+ skb = vnet_skb_shape(skb, &start, &nlen);
+
+ if (unlikely(!skb))
+ goto out_dropped;
+
spin_lock_irqsave(&port->vio.lock, flags);
dr = &port->vio.drings[VIO_DRIVER_TX_RING];
@@ -811,14 +930,27 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
d = vio_dring_cur(dr);
- tx_buf = port->tx_bufs[dr->prod].buf;
- skb_copy_from_linear_data(skb, tx_buf + VNET_PACKET_SKIP, skb->len);
+ txi = dr->prod;
+
+ freeskbs = vnet_clean_tx_ring(port, &pending);
+
+ BUG_ON(port->tx_bufs[txi].skb);
len = skb->len;
- if (len < ETH_ZLEN) {
+ if (len < ETH_ZLEN)
len = ETH_ZLEN;
- memset(tx_buf+VNET_PACKET_SKIP+skb->len, 0, len - skb->len);
+
+ port->tx_bufs[txi].skb = skb;
+ skb = NULL;
+
+ err = ldc_map_single(port->vio.lp, start, nlen,
+ port->tx_bufs[txi].cookies, 2,
+ (LDC_MAP_SHADOW | LDC_MAP_DIRECT | LDC_MAP_RW));
+ if (err < 0) {
+ netdev_info(dev, "tx buffer map error %d\n", err);
+ goto out_dropped_unlock;
}
+ port->tx_bufs[txi].ncookies = err;
/* We don't rely on the ACKs to free the skb in vnet_start_xmit(),
* thus it is safe to not set VIO_ACK_ENABLE for each transmission:
@@ -830,9 +962,9 @@ static int vnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
*/
d->hdr.ack = VIO_ACK_DISABLE;
d->size = len;
- d->ncookies = port->tx_bufs[dr->prod].ncookies;
+ d->ncookies = port->tx_bufs[txi].ncookies;
for (i = 0; i < d->ncookies; i++)
- d->cookies[i] = port->tx_bufs[dr->prod].cookies[i];
+ d->cookies[i] = port->tx_bufs[txi].cookies[i];
/* This has to be a non-SMP write barrier because we are writing
* to memory which is shared with the peer LDOM.
@@ -876,7 +1008,7 @@ ldc_start_done:
port->start_cons = false;
dev->stats.tx_packets++;
- dev->stats.tx_bytes += skb->len;
+ dev->stats.tx_bytes += port->tx_bufs[txi].skb->len;
dr->prod = (dr->prod + 1) & (VNET_TX_RING_SIZE - 1);
if (unlikely(vnet_tx_dring_avail(dr) < 2)) {
@@ -887,7 +1019,9 @@ ldc_start_done:
spin_unlock_irqrestore(&port->vio.lock, flags);
- dev_kfree_skb(skb);
+ vnet_free_skbs(freeskbs);
+
+ (void)mod_timer(&port->clean_timer, jiffies + VNET_CLEAN_TIMEOUT);
return NETDEV_TX_OK;
@@ -895,7 +1029,14 @@ out_dropped_unlock:
spin_unlock_irqrestore(&port->vio.lock, flags);
out_dropped:
- dev_kfree_skb(skb);
+ if (skb)
+ dev_kfree_skb(skb);
+ vnet_free_skbs(freeskbs);
+ if (pending)
+ (void)mod_timer(&port->clean_timer,
+ jiffies + VNET_CLEAN_TIMEOUT);
+ else
+ del_timer(&port->clean_timer);
dev->stats.tx_dropped++;
return NETDEV_TX_OK;
}
@@ -1097,17 +1238,22 @@ static void vnet_port_free_tx_bufs(struct vnet_port *port)
}
for (i = 0; i < VNET_TX_RING_SIZE; i++) {
- void *buf = port->tx_bufs[i].buf;
+ struct vio_net_desc *d;
+ void *skb = port->tx_bufs[i].skb;
- if (!buf)
+ if (!skb)
continue;
+ d = vio_dring_entry(dr, i);
+ if (d->hdr.state == VIO_DESC_READY)
+ pr_warn("active transmit buffers freed\n");
+
ldc_unmap(port->vio.lp,
port->tx_bufs[i].cookies,
port->tx_bufs[i].ncookies);
-
- kfree(buf);
- port->tx_bufs[i].buf = NULL;
+ dev_kfree_skb(skb);
+ port->tx_bufs[i].skb = NULL;
+ d->hdr.state = VIO_DESC_FREE;
}
}
@@ -1118,34 +1264,6 @@ static int vnet_port_alloc_tx_bufs(struct vnet_port *port)
int i, err, ncookies;
void *dring;
- for (i = 0; i < VNET_TX_RING_SIZE; i++) {
- void *buf = kzalloc(VNET_MAXPACKET + 8, GFP_KERNEL);
- int map_len = (VNET_MAXPACKET + 7) & ~7;
-
- err = -ENOMEM;
- if (!buf)
- goto err_out;
-
- err = -EFAULT;
- if ((unsigned long)buf & (8UL - 1)) {
- pr_err("TX buffer misaligned\n");
- kfree(buf);
- goto err_out;
- }
-
- err = ldc_map_single(port->vio.lp, buf, map_len,
- port->tx_bufs[i].cookies, 2,
- (LDC_MAP_SHADOW |
- LDC_MAP_DIRECT |
- LDC_MAP_RW));
- if (err < 0) {
- kfree(buf);
- goto err_out;
- }
- port->tx_bufs[i].buf = buf;
- port->tx_bufs[i].ncookies = err;
- }
-
dr = &port->vio.drings[VIO_DRIVER_TX_RING];
len = (VNET_TX_RING_SIZE *
@@ -1172,6 +1290,12 @@ static int vnet_port_alloc_tx_bufs(struct vnet_port *port)
dr->pending = VNET_TX_RING_SIZE;
dr->ncookies = ncookies;
+ for (i = 0; i < VNET_TX_RING_SIZE; ++i) {
+ struct vio_net_desc *d;
+
+ d = vio_dring_entry(dr, i);
+ d->hdr.state = VIO_DESC_FREE;
+ }
return 0;
err_out:
@@ -1203,6 +1327,8 @@ static struct vnet *vnet_new(const u64 *local_mac)
dev = alloc_etherdev(sizeof(*vp));
if (!dev)
return ERR_PTR(-ENOMEM);
+ dev->needed_headroom = VNET_PACKET_SKIP + 8;
+ dev->needed_tailroom = 8;
for (i = 0; i < ETH_ALEN; i++)
dev->dev_addr[i] = (*local_mac >> (5 - i) * 8) & 0xff;
@@ -1397,6 +1523,9 @@ static int vnet_port_probe(struct vio_dev *vdev, const struct vio_device_id *id)
pr_info("%s: PORT ( remote-mac %pM%s )\n",
vp->dev->name, port->raddr, switch_port ? " switch-port" : "");
+ setup_timer(&port->clean_timer, vnet_clean_timer_expire,
+ (unsigned long)port);
+
vio_port_up(&port->vio);
mdesc_release(hp);
@@ -1423,6 +1552,7 @@ static int vnet_port_remove(struct vio_dev *vdev)
unsigned long flags;
del_timer_sync(&port->vio.timer);
+ del_timer_sync(&port->clean_timer);
spin_lock_irqsave(&vp->lock, flags);
list_del(&port->list);
diff --git a/drivers/net/ethernet/sun/sunvnet.h b/drivers/net/ethernet/sun/sunvnet.h
index 986e04b..02f507d 100644
--- a/drivers/net/ethernet/sun/sunvnet.h
+++ b/drivers/net/ethernet/sun/sunvnet.h
@@ -11,6 +11,11 @@
*/
#define VNET_TX_TIMEOUT (5 * HZ)
+/* length of time (or less) we expect pending descriptors to be marked
+ * as VIO_DESC_DONE and skbs ready to be freed
+ */
+#define VNET_CLEAN_TIMEOUT ((HZ/100)+1)
+
#define VNET_MAXPACKET 1518ULL /* ETH_FRAMELEN + VLAN_HDR */
#define VNET_TX_RING_SIZE 512
#define VNET_TX_WAKEUP_THRESH(dr) ((dr)->pending / 4)
@@ -22,7 +27,7 @@
#define VNET_PACKET_SKIP 6
struct vnet_tx_entry {
- void *buf;
+ struct sk_buff *skb;
unsigned int ncookies;
struct ldc_trans_cookie cookies[2];
};
@@ -46,6 +51,8 @@ struct vnet_port {
bool stop_rx;
bool start_cons;
+ struct timer_list clean_timer;
+
u64 rmtu;
};
--
1.7.1
--
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