net/mlx4_en: add page recycle to prepare rx ring for tx support

The mlx4 driver by default allocates order-3 pages for the ring to
consume in multiple fragments. When the device has an xdp program, this
behavior will prevent tx actions since the page must be re-mapped in
TODEVICE mode, which cannot be done if the page is still shared.

Start by making the allocator configurable based on whether xdp is
running, such that order-0 pages are always used and never shared.

Since this will stress the page allocator, add a simple page cache to
each rx ring. Pages in the cache are left dma-mapped, and in drop-only
stress tests the page allocator is eliminated from the perf report.

Note that setting an xdp program will now require the rings to be
reconfigured.

Before:
 26.91%  ksoftirqd/0  [mlx4_en]         [k] mlx4_en_process_rx_cq
 17.88%  ksoftirqd/0  [mlx4_en]         [k] mlx4_en_alloc_frags
  6.00%  ksoftirqd/0  [mlx4_en]         [k] mlx4_en_free_frag
  4.49%  ksoftirqd/0  [kernel.vmlinux]  [k] get_page_from_freelist
  3.21%  swapper      [kernel.vmlinux]  [k] intel_idle
  2.73%  ksoftirqd/0  [kernel.vmlinux]  [k] bpf_map_lookup_elem
  2.57%  swapper      [mlx4_en]         [k] mlx4_en_process_rx_cq

After:
 31.72%  swapper      [kernel.vmlinux]       [k] intel_idle
  8.79%  swapper      [mlx4_en]              [k] mlx4_en_process_rx_cq
  7.54%  swapper      [kernel.vmlinux]       [k] poll_idle
  6.36%  swapper      [mlx4_core]            [k] mlx4_eq_int
  4.21%  swapper      [kernel.vmlinux]       [k] tasklet_action
  4.03%  swapper      [kernel.vmlinux]       [k] cpuidle_enter_state
  3.43%  swapper      [mlx4_en]              [k] mlx4_en_prepare_rx_desc
  2.18%  swapper      [kernel.vmlinux]       [k] native_irq_return_iret
  1.37%  swapper      [kernel.vmlinux]       [k] menu_select
  1.09%  swapper      [kernel.vmlinux]       [k] bpf_map_lookup_elem

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index c34a33d..47ae2a2 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -2529,12 +2529,33 @@ static int mlx4_en_set_tx_maxrate(struct net_device *dev, int queue_index, u32 m
 static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog)
 {
        struct mlx4_en_priv *priv = netdev_priv(dev);
+       struct mlx4_en_dev *mdev = priv->mdev;
        struct bpf_prog *old_prog;
        int xdp_ring_num;
+       int port_up = 0;
+       int err;
        int i;
 
        xdp_ring_num = prog ? ALIGN(priv->rx_ring_num, MLX4_EN_NUM_UP) : 0;
 
+       /* No need to reconfigure buffers when simply swapping the
+        * program for a new one.
+        */
+       if (priv->xdp_ring_num == xdp_ring_num) {
+               if (prog) {
+                       prog = bpf_prog_add(prog, priv->rx_ring_num - 1);
+                       if (IS_ERR(prog))
+                               return PTR_ERR(prog);
+               }
+               for (i = 0; i < priv->rx_ring_num; i++) {
+                       /* This xchg is paired with READ_ONCE in the fastpath */
+                       old_prog = xchg(&priv->rx_ring[i]->xdp_prog, prog);
+                       if (old_prog)
+                               bpf_prog_put(old_prog);
+               }
+               return 0;
+       }
+
        if (priv->num_frags > 1) {
                en_err(priv, "Cannot set XDP if MTU requires multiple frags\n");
                return -EOPNOTSUPP;
@@ -2546,15 +2567,30 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog)
                        return PTR_ERR(prog);
        }
 
+       mutex_lock(&mdev->state_lock);
+       if (priv->port_up) {
+               port_up = 1;
+               mlx4_en_stop_port(dev, 1);
+       }
+
        priv->xdp_ring_num = xdp_ring_num;
 
-       /* This xchg is paired with READ_ONCE in the fast path */
        for (i = 0; i < priv->rx_ring_num; i++) {
                old_prog = xchg(&priv->rx_ring[i]->xdp_prog, prog);
                if (old_prog)
                        bpf_prog_put(old_prog);
        }
 
+       if (port_up) {
+               err = mlx4_en_start_port(dev);
+               if (err) {
+                       en_err(priv, "Failed starting port %d for XDP change\n",
+                              priv->port);
+                       queue_work(mdev->workqueue, &priv->watchdog_task);
+               }
+       }
+
+       mutex_unlock(&mdev->state_lock);
        return 0;
 }
 

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
index 6729545..9dd5dc1 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
@@ -58,7 +58,7 @@ static int mlx4_alloc_pages(struct mlx4_en_priv *priv,
        struct page *page;
        dma_addr_t dma;
 
-       for (order = MLX4_EN_ALLOC_PREFER_ORDER; ;) {
+       for (order = frag_info->order; ;) {
                gfp_t gfp = _gfp;
 
                if (order)
@@ -71,7 +71,7 @@ static int mlx4_alloc_pages(struct mlx4_en_priv *priv,
                        return -ENOMEM;
        }
        dma = dma_map_page(priv->ddev, page, 0, PAGE_SIZE << order,
-                          PCI_DMA_FROMDEVICE);
+                          frag_info->dma_dir);
        if (dma_mapping_error(priv->ddev, dma)) {
                put_page(page);
                return -ENOMEM;
@@ -125,7 +125,8 @@ out:
        while (i--) {
                if (page_alloc[i].page != ring_alloc[i].page) {
                        dma_unmap_page(priv->ddev, page_alloc[i].dma,
-                               page_alloc[i].page_size, PCI_DMA_FROMDEVICE);
+                               page_alloc[i].page_size,
+                               priv->frag_info[i].dma_dir);
                        page = page_alloc[i].page;
                        /* Revert changes done by mlx4_alloc_pages */
                        page_ref_sub(page, page_alloc[i].page_size /
@@ -146,7 +147,7 @@ static void mlx4_en_free_frag(struct mlx4_en_priv *priv,
 
        if (next_frag_end > frags[i].page_size)
                dma_unmap_page(priv->ddev, frags[i].dma, frags[i].page_size,
-                              PCI_DMA_FROMDEVICE);
+                              frag_info->dma_dir);
 
        if (frags[i].page)
                put_page(frags[i].page);
@@ -177,7 +178,8 @@ out:
 
                page_alloc = &ring->page_alloc[i];
                dma_unmap_page(priv->ddev, page_alloc->dma,
-                              page_alloc->page_size, PCI_DMA_FROMDEVICE);
+                              page_alloc->page_size,
+                              priv->frag_info[i].dma_dir);
                page = page_alloc->page;
                /* Revert changes done by mlx4_alloc_pages */
                page_ref_sub(page, page_alloc->page_size /
@@ -202,7 +204,7 @@ static void mlx4_en_destroy_allocator(struct mlx4_en_priv *priv,
                       i, page_count(page_alloc->page));
 
                dma_unmap_page(priv->ddev, page_alloc->dma,
-                               page_alloc->page_size, PCI_DMA_FROMDEVICE);
+                               page_alloc->page_size, frag_info->dma_dir);
                while (page_alloc->page_offset + frag_info->frag_stride <
                       page_alloc->page_size) {
                        put_page(page_alloc->page);
@@ -245,6 +247,12 @@ static int mlx4_en_prepare_rx_desc(struct mlx4_en_priv *priv,
        struct mlx4_en_rx_alloc *frags = ring->rx_info +
                                        (index << priv->log_rx_info);
 
+       if (ring->page_cache.index > 0) {
+               frags[0] = ring->page_cache.buf[--ring->page_cache.index];
+               rx_desc->data[0].addr = cpu_to_be64(frags[0].dma);
+               return 0;
+       }
+
        return mlx4_en_alloc_frags(priv, rx_desc, frags, ring->page_alloc, gfp);
 }
 
@@ -503,6 +511,24 @@ void mlx4_en_recover_from_oom(struct mlx4_en_priv *priv)
        }
 }
 
+/* When the rx ring is running in page-per-packet mode, a released frame can go
+ * directly into a small cache, to avoid unmapping or touching the page
+ * allocator. In bpf prog performance scenarios, buffers are either forwarded
+ * or dropped, never converted to skbs, so every page can come directly from
+ * this cache when it is sized to be a multiple of the napi budget.
+ */
+bool mlx4_en_rx_recycle(struct mlx4_en_rx_ring *ring,
+                       struct mlx4_en_rx_alloc *frame)
+{
+       struct mlx4_en_page_cache *cache = &ring->page_cache;
+
+       if (cache->index >= MLX4_EN_CACHE_SIZE)
+               return false;
+
+       cache->buf[cache->index++] = *frame;
+       return true;
+}
+
 void mlx4_en_destroy_rx_ring(struct mlx4_en_priv *priv,
                             struct mlx4_en_rx_ring **pring,
                             u32 size, u16 stride)
@@ -525,6 +551,16 @@ void mlx4_en_destroy_rx_ring(struct mlx4_en_priv *priv,
 void mlx4_en_deactivate_rx_ring(struct mlx4_en_priv *priv,
                                struct mlx4_en_rx_ring *ring)
 {
+       int i;
+
+       for (i = 0; i < ring->page_cache.index; i++) {
+               struct mlx4_en_rx_alloc *frame = &ring->page_cache.buf[i];
+
+               dma_unmap_page(priv->ddev, frame->dma, frame->page_size,
+                              priv->frag_info[0].dma_dir);
+               put_page(frame->page);
+       }
+       ring->page_cache.index = 0;
        mlx4_en_free_rx_buf(priv, ring);
        if (ring->stride <= TXBB_SIZE)
                ring->buf -= TXBB_SIZE;
@@ -866,6 +902,8 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
                                bpf_warn_invalid_xdp_action(act);
                        case XDP_ABORTED:
                        case XDP_DROP:
+                               if (mlx4_en_rx_recycle(ring, frags))
+                                       goto consumed;
                                goto next;
                        }
                }
@@ -1021,6 +1059,7 @@ next:
                for (nr = 0; nr < priv->num_frags; nr++)
                        mlx4_en_free_frag(priv, frags, nr);
 
+consumed:
                ++cq->mcq.cons_index;
                index = (cq->mcq.cons_index) & ring->size_mask;
                cqe = mlx4_en_get_cqe(cq->buf, index, priv->cqe_size) + factor;
@@ -1096,19 +1135,34 @@ static const int frag_sizes[] = {
 
 void mlx4_en_calc_rx_buf(struct net_device *dev)
 {
+       enum dma_data_direction dma_dir = PCI_DMA_FROMDEVICE;
        struct mlx4_en_priv *priv = netdev_priv(dev);
        int eff_mtu = MLX4_EN_EFF_MTU(dev->mtu);
+       int order = MLX4_EN_ALLOC_PREFER_ORDER;
+       u32 align = SMP_CACHE_BYTES;
        int buf_size = 0;
        int i = 0;
 
+       /* bpf requires buffers to be set up as 1 packet per page.
+        * This only works when num_frags == 1.
+        */
+       if (priv->xdp_ring_num) {
+               /* This will gain efficient xdp frame recycling at the expense
+                * of more costly truesize accounting
+                */
+               align = PAGE_SIZE;
+               order = 0;
+       }
+
        while (buf_size < eff_mtu) {
+               priv->frag_info[i].order = order;
                priv->frag_info[i].frag_size =
                        (eff_mtu > buf_size + frag_sizes[i]) ?
                                frag_sizes[i] : eff_mtu - buf_size;
                priv->frag_info[i].frag_prefix_size = buf_size;
                priv->frag_info[i].frag_stride =
-                               ALIGN(priv->frag_info[i].frag_size,
-                                     SMP_CACHE_BYTES);
+                               ALIGN(priv->frag_info[i].frag_size, align);
+               priv->frag_info[i].dma_dir = dma_dir;
                buf_size += priv->frag_info[i].frag_size;
                i++;
        }

diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
index eb1238d..eff4be0 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
+++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
@@ -259,6 +259,12 @@ struct mlx4_en_rx_alloc {
        u32             page_size;
 };
 
+#define MLX4_EN_CACHE_SIZE (2 * NAPI_POLL_WEIGHT)
+struct mlx4_en_page_cache {
+       u32 index;
+       struct mlx4_en_rx_alloc buf[MLX4_EN_CACHE_SIZE];
+};
+
 struct mlx4_en_tx_ring {
        /* cache line used and dirtied in tx completion
         * (mlx4_en_free_tx_buf())
@@ -324,6 +330,7 @@ struct mlx4_en_rx_ring {
        void *buf;
        void *rx_info;
        struct bpf_prog *xdp_prog;
+       struct mlx4_en_page_cache page_cache;
        unsigned long bytes;
        unsigned long packets;
        unsigned long csum_ok;
@@ -443,7 +450,9 @@ struct mlx4_en_mc_list {
 struct mlx4_en_frag_info {
        u16 frag_size;
        u16 frag_prefix_size;
-       u16 frag_stride;
+       u32 frag_stride;
+       enum dma_data_direction dma_dir;
+       int order;
 };
 
 #ifdef CONFIG_MLX4_EN_DCB