From 8e845f4cbbd2ef81846c2ab5dca46d88fb2717ee Mon Sep 17 00:00:00 2001 From: David L Stevens Date: Mon, 29 Sep 2014 19:48:11 -0400 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- 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; }; -- 2.7.4