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net/mlx4_en: add page recycle to prepare rx ring for tx support
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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>
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Brenden Blanco authored and David S. Miller committed Jul 20, 2016
1 parent 86af8b4 commit d576acf
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Showing 3 changed files with 109 additions and 10 deletions.
38 changes: 37 additions & 1 deletion drivers/net/ethernet/mellanox/mlx4/en_netdev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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;
}

Expand Down
70 changes: 62 additions & 8 deletions drivers/net/ethernet/mellanox/mlx4/en_rx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
Expand All @@ -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;
Expand Down Expand Up @@ -125,7 +125,8 @@ static int mlx4_en_alloc_frags(struct mlx4_en_priv *priv,
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 /
Expand All @@ -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);
Expand Down Expand Up @@ -177,7 +178,8 @@ static int mlx4_en_init_allocator(struct mlx4_en_priv *priv,

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 /
Expand All @@ -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);
Expand Down Expand Up @@ -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);
}

Expand Down Expand Up @@ -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)
Expand All @@ -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;
Expand Down Expand Up @@ -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;
}
}
Expand Down Expand Up @@ -1021,6 +1059,7 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
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;
Expand Down Expand Up @@ -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++;
}
Expand Down
11 changes: 10 additions & 1 deletion drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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())
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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
Expand Down

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