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authorJesper Dangaard Brouer <brouer@redhat.com>2018-04-17 17:46:32 +0300
committerDavid S. Miller <davem@davemloft.net>2018-04-17 17:50:29 +0300
commit039930945a72d9af5ff04ae9b9e60658a52e0770 (patch)
treee92821099697576bcdcd41e9d61f561be0e6923c /drivers/net
parent60bbf7eeef10dc647430646d7fe5e3d8d132dbec (diff)
downloadlinux-039930945a72d9af5ff04ae9b9e60658a52e0770.tar.xz
xdp: transition into using xdp_frame for return API
Changing API xdp_return_frame() to take struct xdp_frame as argument, seems like a natural choice. But there are some subtle performance details here that needs extra care, which is a deliberate choice. When de-referencing xdp_frame on a remote CPU during DMA-TX completion, result in the cache-line is change to "Shared" state. Later when the page is reused for RX, then this xdp_frame cache-line is written, which change the state to "Modified". This situation already happens (naturally) for, virtio_net, tun and cpumap as the xdp_frame pointer is the queued object. In tun and cpumap, the ptr_ring is used for efficiently transferring cache-lines (with pointers) between CPUs. Thus, the only option is to de-referencing xdp_frame. It is only the ixgbe driver that had an optimization, in which it can avoid doing the de-reference of xdp_frame. The driver already have TX-ring queue, which (in case of remote DMA-TX completion) have to be transferred between CPUs anyhow. In this data area, we stored a struct xdp_mem_info and a data pointer, which allowed us to avoid de-referencing xdp_frame. To compensate for this, a prefetchw is used for telling the cache coherency protocol about our access pattern. My benchmarks show that this prefetchw is enough to compensate the ixgbe driver. V7: Adjust for commit d9314c474d4f ("i40e: add support for XDP_REDIRECT") V8: Adjust for commit bd658dda4237 ("net/mlx5e: Separate dma base address and offset in dma_sync call") Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net')
-rw-r--r--drivers/net/ethernet/intel/i40e/i40e_txrx.c5
-rw-r--r--drivers/net/ethernet/intel/ixgbe/ixgbe.h4
-rw-r--r--drivers/net/ethernet/intel/ixgbe/ixgbe_main.c17
-rw-r--r--drivers/net/ethernet/mellanox/mlx5/core/en_rx.c1
-rw-r--r--drivers/net/tun.c4
-rw-r--r--drivers/net/virtio_net.c2
6 files changed, 18 insertions, 15 deletions
diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 96c54cbfb1f9..c8bf4d35fdea 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -638,8 +638,7 @@ static void i40e_unmap_and_free_tx_resource(struct i40e_ring *ring,
if (tx_buffer->tx_flags & I40E_TX_FLAGS_FD_SB)
kfree(tx_buffer->raw_buf);
else if (ring_is_xdp(ring))
- xdp_return_frame(tx_buffer->xdpf->data,
- &tx_buffer->xdpf->mem);
+ xdp_return_frame(tx_buffer->xdpf);
else
dev_kfree_skb_any(tx_buffer->skb);
if (dma_unmap_len(tx_buffer, len))
@@ -842,7 +841,7 @@ static bool i40e_clean_tx_irq(struct i40e_vsi *vsi,
/* free the skb/XDP data */
if (ring_is_xdp(tx_ring))
- xdp_return_frame(tx_buf->xdpf->data, &tx_buf->xdpf->mem);
+ xdp_return_frame(tx_buf->xdpf);
else
napi_consume_skb(tx_buf->skb, napi_budget);
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
index abb5248e917e..7dd5038cfcc4 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
@@ -241,8 +241,7 @@ struct ixgbe_tx_buffer {
unsigned long time_stamp;
union {
struct sk_buff *skb;
- /* XDP uses address ptr on irq_clean */
- void *data;
+ struct xdp_frame *xdpf;
};
unsigned int bytecount;
unsigned short gso_segs;
@@ -250,7 +249,6 @@ struct ixgbe_tx_buffer {
DEFINE_DMA_UNMAP_ADDR(dma);
DEFINE_DMA_UNMAP_LEN(len);
u32 tx_flags;
- struct xdp_mem_info xdp_mem;
};
struct ixgbe_rx_buffer {
diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index f10904ec2172..4f2864165723 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -1216,7 +1216,7 @@ static bool ixgbe_clean_tx_irq(struct ixgbe_q_vector *q_vector,
/* free the skb */
if (ring_is_xdp(tx_ring))
- xdp_return_frame(tx_buffer->data, &tx_buffer->xdp_mem);
+ xdp_return_frame(tx_buffer->xdpf);
else
napi_consume_skb(tx_buffer->skb, napi_budget);
@@ -2386,6 +2386,7 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
xdp.data_hard_start = xdp.data -
ixgbe_rx_offset(rx_ring);
xdp.data_end = xdp.data + size;
+ prefetchw(xdp.data_hard_start); /* xdp_frame write */
skb = ixgbe_run_xdp(adapter, rx_ring, &xdp);
}
@@ -5797,7 +5798,7 @@ static void ixgbe_clean_tx_ring(struct ixgbe_ring *tx_ring)
/* Free all the Tx ring sk_buffs */
if (ring_is_xdp(tx_ring))
- xdp_return_frame(tx_buffer->data, &tx_buffer->xdp_mem);
+ xdp_return_frame(tx_buffer->xdpf);
else
dev_kfree_skb_any(tx_buffer->skb);
@@ -8348,16 +8349,21 @@ static int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,
struct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()];
struct ixgbe_tx_buffer *tx_buffer;
union ixgbe_adv_tx_desc *tx_desc;
+ struct xdp_frame *xdpf;
u32 len, cmd_type;
dma_addr_t dma;
u16 i;
- len = xdp->data_end - xdp->data;
+ xdpf = convert_to_xdp_frame(xdp);
+ if (unlikely(!xdpf))
+ return -EOVERFLOW;
+
+ len = xdpf->len;
if (unlikely(!ixgbe_desc_unused(ring)))
return IXGBE_XDP_CONSUMED;
- dma = dma_map_single(ring->dev, xdp->data, len, DMA_TO_DEVICE);
+ dma = dma_map_single(ring->dev, xdpf->data, len, DMA_TO_DEVICE);
if (dma_mapping_error(ring->dev, dma))
return IXGBE_XDP_CONSUMED;
@@ -8372,8 +8378,7 @@ static int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,
dma_unmap_len_set(tx_buffer, len, len);
dma_unmap_addr_set(tx_buffer, dma, dma);
- tx_buffer->data = xdp->data;
- tx_buffer->xdp_mem = xdp->rxq->mem;
+ tx_buffer->xdpf = xdpf;
tx_desc->read.buffer_addr = cpu_to_le64(dma);
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index f42436d7f2d9..7bbf0db27a01 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -890,6 +890,7 @@ struct sk_buff *skb_from_cqe(struct mlx5e_rq *rq, struct mlx5_cqe64 *cqe,
dma_sync_single_range_for_cpu(rq->pdev, di->addr, wi->offset,
frag_size, DMA_FROM_DEVICE);
+ prefetchw(va); /* xdp_frame data area */
prefetch(data);
wi->offset += frag_size;
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 283bde85c455..bec130cdbd9d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -663,7 +663,7 @@ void tun_ptr_free(void *ptr)
if (tun_is_xdp_frame(ptr)) {
struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
- xdp_return_frame(xdpf->data, &xdpf->mem);
+ xdp_return_frame(xdpf);
} else {
__skb_array_destroy_skb(ptr);
}
@@ -2196,7 +2196,7 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
struct xdp_frame *xdpf = tun_ptr_to_xdp(ptr);
ret = tun_put_user_xdp(tun, tfile, xdpf, to);
- xdp_return_frame(xdpf->data, &xdpf->mem);
+ xdp_return_frame(xdpf);
} else {
struct sk_buff *skb = ptr;
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 42d338fe9a8d..ab3d7cbc4c49 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -430,7 +430,7 @@ static int __virtnet_xdp_xmit(struct virtnet_info *vi,
/* Free up any pending old buffers before queueing new ones. */
while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
- xdp_return_frame(xdpf_sent->data, &xdpf_sent->mem);
+ xdp_return_frame(xdpf_sent);
xdpf = convert_to_xdp_frame(xdp);
if (unlikely(!xdpf))