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 <bbla...@plumgrid.com>
---
drivers/net/ethernet/mellanox/mlx4/en_ethtool.c | 2 +-
drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 46 +++++++++++++++--
drivers/net/ethernet/mellanox/mlx4/en_rx.c | 69 ++++++++++++++++++++++---
drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 12 ++++-
4 files changed, 115 insertions(+), 14 deletions(-)
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
b/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
index 51a2e82..d3d51fa 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_ethtool.c
@@ -47,7 +47,7 @@
#define EN_ETHTOOL_SHORT_MASK cpu_to_be16(0xffff)
#define EN_ETHTOOL_WORD_MASK cpu_to_be32(0xffffffff)
-static int mlx4_en_moderation_update(struct mlx4_en_priv *priv)
+int mlx4_en_moderation_update(struct mlx4_en_priv *priv)
{
int i;
int err = 0;
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index 5c6b1a0c..2883315 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -2532,19 +2532,57 @@ 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 port_up = 0;
+ int err;
+
+ /* No need to reconfigure buffers when simply swapping the
+ * program for a new one.
+ */
+ if (READ_ONCE(priv->prog) && prog) {
+ /* This xchg is paired with READ_ONCE in the fast path, but is
+ * also protected from itself via rtnl lock
+ */
+ old_prog = xchg(&priv->prog, prog);
+ if (old_prog)
+ bpf_prog_put(old_prog);
+ return 0;
+ }
if (priv->num_frags > 1)
return -EOPNOTSUPP;
- /* This xchg is paired with READ_ONCE in the fast path, but is
- * also protected from itself via rtnl lock
- */
+ mutex_lock(&mdev->state_lock);
+ if (priv->port_up) {
+ port_up = 1;
+ mlx4_en_stop_port(dev, 1);
+ }
+
+ mlx4_en_free_resources(priv);
+
old_prog = xchg(&priv->prog, prog);
if (old_prog)
bpf_prog_put(old_prog);
- return 0;
+ err = mlx4_en_alloc_resources(priv);
+ if (err) {
+ en_err(priv, "Failed reallocating port resources\n");
+ goto out;
+ }
+ if (port_up) {
+ err = mlx4_en_start_port(dev);
+ if (err)
+ en_err(priv, "Failed starting port\n");
+ }
+
+ err = mlx4_en_moderation_update(priv);
+
+out:
+ if (err)
+ priv->prog = NULL;
+ mutex_unlock(&mdev->state_lock);
+ return err;
}
static bool mlx4_xdp_attached(struct net_device *dev)
diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
index 2bf3d62..02d63a0 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
@@ -57,7 +57,7 @@ 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)
@@ -70,7 +70,7 @@ 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;
@@ -124,7 +124,8 @@ 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 /
@@ -145,7 +146,7 @@ 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);
@@ -176,7 +177,8 @@ 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 /
@@ -201,7 +203,7 @@ 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);
@@ -244,6 +246,12 @@ 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);
}
@@ -502,12 +510,39 @@ 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)
{
struct mlx4_en_dev *mdev = priv->mdev;
struct mlx4_en_rx_ring *ring = *pring;
+ 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);
+ }
mlx4_free_hwq_res(mdev->dev, &ring->wqres, size * stride + TXBB_SIZE);
vfree(ring->rx_info);
@@ -862,6 +897,8 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct
mlx4_en_cq *cq, int bud
default:
bpf_warn_invalid_xdp_action(act);
case XDP_DROP:
+ if (mlx4_en_rx_recycle(ring, frags))
+ goto consumed;
goto next;
}
}
@@ -1017,6 +1054,7 @@ 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;
@@ -1092,19 +1130,34 @@ 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->prog) {
+ /* 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 35ecfa2..0e0ecd1 100644
--- 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())
@@ -323,6 +329,7 @@ struct mlx4_en_rx_ring {
u8 fcs_del;
void *buf;
void *rx_info;
+ struct mlx4_en_page_cache page_cache;
unsigned long bytes;
unsigned long packets;
unsigned long csum_ok;
@@ -442,7 +449,9 @@ 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
@@ -654,6 +663,7 @@ void mlx4_en_set_stats_bitmap(struct mlx4_dev *dev,
void mlx4_en_free_resources(struct mlx4_en_priv *priv);
int mlx4_en_alloc_resources(struct mlx4_en_priv *priv);
+int mlx4_en_moderation_update(struct mlx4_en_priv *priv);
int mlx4_en_create_cq(struct mlx4_en_priv *priv, struct mlx4_en_cq **pcq,
int entries, int ring, enum cq_type mode, int node);
--
2.8.2
