On Wed, Jan 28, 2015 at 12:36:27PM +0100, Yann Droneaud wrote:
> Hi,
>
> Le mardi 27 janvier 2015 à 03:21 -0800, Yuval Shaia a écrit :
> > With this fix Scatter-Gather will be supported also in connected mode
> >
>
> Please explain the issue with current kernel and the advantage
> of the proposed fix in the commit message. Perhaps benchmarks
> against various HCAs would be welcome.
The benefits of using SG are well known.
I think the question should be the other way around - why not supporting SG in CM?
I will add the following text to commit message:
By default, IPoIB-CM driver uses 64k MTU. Larger MTU gives better performance.
This MTU plus overhead puts the memory allocation for IP based packets at 32 4k pages (order 5), which have to be contiguous.
When the system memory under pressure, it was observed that allocating 128k contiguous physical memory is difficult and causes serious errors (such as system becomes unusable).
This enhancement resolve the issue by removing the physically contiguous memory requirement using Scatter/Gather feature that exists in Linux stack.
>
> > Signed-off-by: Yuval Shaia <yuval.shaia@xxxxxxxxxx>
> > ---
> > drivers/infiniband/ulp/ipoib/ipoib.h | 8 +--
> > drivers/infiniband/ulp/ipoib/ipoib_cm.c | 107 +++++++++++++++++++++++------
> > drivers/infiniband/ulp/ipoib/ipoib_ib.c | 3 +-
> > drivers/infiniband/ulp/ipoib/ipoib_main.c | 3 +-
> > 4 files changed, 91 insertions(+), 30 deletions(-)
> >
> > diff --git a/drivers/infiniband/ulp/ipoib/ipoib.h b/drivers/infiniband/ulp/ipoib/ipoib.h
> > index d7562be..fb42834 100644
> > --- a/drivers/infiniband/ulp/ipoib/ipoib.h
> > +++ b/drivers/infiniband/ulp/ipoib/ipoib.h
> > @@ -170,11 +170,6 @@ struct ipoib_tx_buf {
> > u64 mapping[MAX_SKB_FRAGS + 1];
> > };
> >
> > -struct ipoib_cm_tx_buf {
> > - struct sk_buff *skb;
> > - u64 mapping;
> > -};
> > -
> > struct ib_cm_id;
> >
> > struct ipoib_cm_data {
> > @@ -233,7 +228,7 @@ struct ipoib_cm_tx {
> > struct net_device *dev;
> > struct ipoib_neigh *neigh;
> > struct ipoib_path *path;
> > - struct ipoib_cm_tx_buf *tx_ring;
> > + struct ipoib_tx_buf *tx_ring;
> > unsigned tx_head;
> > unsigned tx_tail;
> > unsigned long flags;
> > @@ -496,6 +491,7 @@ int ipoib_mcast_stop_thread(struct net_device *dev, int flush);
> >
> > void ipoib_mcast_dev_down(struct net_device *dev);
> > void ipoib_mcast_dev_flush(struct net_device *dev);
> > +int ipoib_dma_map_tx(struct ib_device *ca, struct ipoib_tx_buf *tx_req);
> >
> > #ifdef CONFIG_INFINIBAND_IPOIB_DEBUG
> > struct ipoib_mcast_iter *ipoib_mcast_iter_init(struct net_device *dev);
> > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> > index 933efce..056e4d2 100644
> > --- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> > +++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> > @@ -88,6 +88,31 @@ static void ipoib_cm_dma_unmap_rx(struct ipoib_dev_priv *priv, int frags,
> > ib_dma_unmap_page(priv->ca, mapping[i + 1], PAGE_SIZE, DMA_FROM_DEVICE);
> > }
> >
> > +static void ipoib_cm_dma_unmap_tx(struct ipoib_dev_priv *priv,
> > + struct ipoib_tx_buf *tx_req)
> > +{
> > + struct sk_buff *skb;
> > + int i, offs;
> > +
> > + skb = tx_req->skb;
> > + if (skb_shinfo(skb)->nr_frags) {
> > + offs = 0;
> > + if (skb_headlen(skb)) {
> > + ib_dma_unmap_single(priv->ca, tx_req->mapping[0],
> > + skb_headlen(skb), DMA_TO_DEVICE);
> > + offs = 1;
> > + }
> > + for (i = 0; i < skb_shinfo(skb)->nr_frags; ++i) {
> > + const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
> > +
> > + ib_dma_unmap_single(priv->ca, tx_req->mapping[i + offs],
> > + skb_frag_size(frag), DMA_TO_DEVICE);
> > + }
> > + } else
> > + ib_dma_unmap_single(priv->ca, tx_req->mapping[0], skb->len,
> > + DMA_TO_DEVICE);
> > +}
> > +
> > static int ipoib_cm_post_receive_srq(struct net_device *dev, int id)
> > {
> > struct ipoib_dev_priv *priv = netdev_priv(dev);
> > @@ -707,11 +732,39 @@ static inline int post_send(struct ipoib_dev_priv *priv,
> > return ib_post_send(tx->qp, &priv->tx_wr, &bad_wr);
> > }
> >
> > +static inline int post_send_sg(struct ipoib_dev_priv *priv,
> > + struct ipoib_cm_tx *tx,
> > + unsigned int wr_id,
> > + struct sk_buff *skb,
> > + u64 mapping[MAX_SKB_FRAGS + 1])
> > +{
> > + struct ib_send_wr *bad_wr;
> > + int i, off;
> > + skb_frag_t *frags = skb_shinfo(skb)->frags;
> > + int nr_frags = skb_shinfo(skb)->nr_frags;
> > +
> > + if (skb_headlen(skb)) {
> > + priv->tx_sge[0].addr = mapping[0];
> > + priv->tx_sge[0].length = skb_headlen(skb);
> > + off = 1;
> > + } else
> > + off = 0;
> > +
> > + for (i = 0; i < nr_frags; ++i) {
> > + priv->tx_sge[i + off].addr = mapping[i + off];
> > + priv->tx_sge[i + off].length = frags[i].size;
> > + }
> > + priv->tx_wr.num_sge = nr_frags + off;
> > + priv->tx_wr.wr_id = wr_id | IPOIB_OP_CM;
> > +
> > + return ib_post_send(tx->qp, &priv->tx_wr, &bad_wr);
> > +}
> > +
> > void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_tx *tx)
> > {
> > struct ipoib_dev_priv *priv = netdev_priv(dev);
> > - struct ipoib_cm_tx_buf *tx_req;
> > - u64 addr;
> > + struct ipoib_tx_buf *tx_req;
> > + u64 addr = 0;
> > int rc;
> >
> > if (unlikely(skb->len > tx->mtu)) {
> > @@ -735,24 +788,37 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
> > */
> > tx_req = &tx->tx_ring[tx->tx_head & (ipoib_sendq_size - 1)];
> > tx_req->skb = skb;
> > - addr = ib_dma_map_single(priv->ca, skb->data, skb->len, DMA_TO_DEVICE);
> > - if (unlikely(ib_dma_mapping_error(priv->ca, addr))) {
> > - ++dev->stats.tx_errors;
> > - dev_kfree_skb_any(skb);
> > - return;
> > - }
> >
> > - tx_req->mapping = addr;
> > + if (skb_shinfo(skb)->nr_frags) {
> > + if (unlikely(ipoib_dma_map_tx(priv->ca, tx_req))) {
> > + ++dev->stats.tx_errors;
> > + dev_kfree_skb_any(skb);
> > + return;
> > + }
> > + rc = post_send_sg(priv, tx, tx->tx_head &
> > + (ipoib_sendq_size - 1),
> > + skb, tx_req->mapping);
> > + } else {
> > + addr = ib_dma_map_single(priv->ca, skb->data, skb->len,
> > + DMA_TO_DEVICE);
> > + if (unlikely(ib_dma_mapping_error(priv->ca, addr))) {
> > + ++dev->stats.tx_errors;
> > + dev_kfree_skb_any(skb);
> > + return;
> > + }
> > +
> > + tx_req->mapping[0] = addr;
> >
> > - skb_orphan(skb);
> > - skb_dst_drop(skb);
> > + skb_orphan(skb);
> > + skb_dst_drop(skb);
> >
> > - rc = post_send(priv, tx, tx->tx_head & (ipoib_sendq_size - 1),
> > - addr, skb->len);
> > + rc = post_send(priv, tx, tx->tx_head & (ipoib_sendq_size - 1),
> > + addr, skb->len);
> > + }
> > if (unlikely(rc)) {
> > ipoib_warn(priv, "post_send failed, error %d\n", rc);
> > ++dev->stats.tx_errors;
> > - ib_dma_unmap_single(priv->ca, addr, skb->len, DMA_TO_DEVICE);
> > + ipoib_cm_dma_unmap_tx(priv, tx_req);
> > dev_kfree_skb_any(skb);
> > } else {
> > dev->trans_start = jiffies;
> > @@ -777,7 +843,7 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
> > struct ipoib_dev_priv *priv = netdev_priv(dev);
> > struct ipoib_cm_tx *tx = wc->qp->qp_context;
> > unsigned int wr_id = wc->wr_id & ~IPOIB_OP_CM;
> > - struct ipoib_cm_tx_buf *tx_req;
> > + struct ipoib_tx_buf *tx_req;
> > unsigned long flags;
> >
> > ipoib_dbg_data(priv, "cm send completion: id %d, status: %d\n",
> > @@ -791,7 +857,7 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
> >
> > tx_req = &tx->tx_ring[wr_id];
> >
> > - ib_dma_unmap_single(priv->ca, tx_req->mapping, tx_req->skb->len, DMA_TO_DEVICE);
> > + ipoib_cm_dma_unmap_tx(priv, tx_req);
> >
> > /* FIXME: is this right? Shouldn't we only increment on success? */
> > ++dev->stats.tx_packets;
> > @@ -1036,6 +1102,9 @@ static struct ib_qp *ipoib_cm_create_tx_qp(struct net_device *dev, struct ipoib_
> >
> > struct ib_qp *tx_qp;
> >
> > + if (dev->features & NETIF_F_SG)
> > + attr.cap.max_send_sge = MAX_SKB_FRAGS + 1;
> > +
> > tx_qp = ib_create_qp(priv->pd, &attr);
> > if (PTR_ERR(tx_qp) == -EINVAL) {
> > ipoib_warn(priv, "can't use GFP_NOIO for QPs on device %s, using GFP_KERNEL\n",
> > @@ -1170,7 +1239,7 @@ err_tx:
> > static void ipoib_cm_tx_destroy(struct ipoib_cm_tx *p)
> > {
> > struct ipoib_dev_priv *priv = netdev_priv(p->dev);
> > - struct ipoib_cm_tx_buf *tx_req;
> > + struct ipoib_tx_buf *tx_req;
> > unsigned long begin;
> >
> > ipoib_dbg(priv, "Destroy active connection 0x%x head 0x%x tail 0x%x\n",
> > @@ -1197,8 +1266,7 @@ timeout:
> >
> > while ((int) p->tx_tail - (int) p->tx_head < 0) {
> > tx_req = &p->tx_ring[p->tx_tail & (ipoib_sendq_size - 1)];
> > - ib_dma_unmap_single(priv->ca, tx_req->mapping, tx_req->skb->len,
> > - DMA_TO_DEVICE);
> > + ipoib_cm_dma_unmap_tx(priv, tx_req);
> > dev_kfree_skb_any(tx_req->skb);
> > ++p->tx_tail;
> > netif_tx_lock_bh(p->dev);
> > @@ -1455,7 +1523,6 @@ static void ipoib_cm_stale_task(struct work_struct *work)
> > spin_unlock_irq(&priv->lock);
> > }
> >
> > -
>
> No need to remove this line.
>
> > static ssize_t show_mode(struct device *d, struct device_attribute *attr,
> > char *buf)
> > {
> > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
> > index 72626c3..9e11447 100644
> > --- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
> > +++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
> > @@ -312,8 +312,7 @@ repost:
> > "for buf %d\n", wr_id);
> > }
> >
> > -static int ipoib_dma_map_tx(struct ib_device *ca,
> > - struct ipoib_tx_buf *tx_req)
> > +int ipoib_dma_map_tx(struct ib_device *ca, struct ipoib_tx_buf *tx_req)
> > {
> > struct sk_buff *skb = tx_req->skb;
> > u64 *mapping = tx_req->mapping;
> > diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> > index 58b5aa3..f9314c6 100644
> > --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
> > +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
> > @@ -190,7 +190,7 @@ static netdev_features_t ipoib_fix_features(struct net_device *dev, netdev_featu
> > struct ipoib_dev_priv *priv = netdev_priv(dev);
> >
> > if (test_bit(IPOIB_FLAG_ADMIN_CM, &priv->flags))
> > - features &= ~(NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO);
> > + features &= ~(NETIF_F_IP_CSUM | NETIF_F_TSO);
> >
> > return features;
> > }
> > @@ -233,7 +233,6 @@ int ipoib_set_mode(struct net_device *dev, const char *buf)
> > "will cause multicast packet drops\n");
> > netdev_update_features(dev);
> > rtnl_unlock();
> > - priv->tx_wr.send_flags &= ~IB_SEND_IP_CSUM;
>
> Sure about this removal ? I don't see it related to scatter-gather.
>
> >
> > ipoib_flush_paths(dev);
> > rtnl_lock();
>
> Regards.
>
> --
> Yann Droneaud
> OPTEYA
>
>
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