[bpf-next V3 PATCH 13/15] mlx5: use page_pool for xdp_return_frame call

Jesper Dangaard Brouer
2018-03-09T20:56:11Z

This patch shows how it is possible to have both the driver local page
cache, which uses elevated refcnt for "catching"/avoiding SKB
put_page. And at the same time, have pages getting returned to the
page_pool from ndp_xdp_xmit DMA completion.

Performance is surprisingly good. Tested DMA-TX completion on ixgbe,
that calls "xdp_return_frame", which call page_pool_put_page().
Stats show DMA-TX-completion runs on CPU#9 and mlx5 RX runs on CPU#5.
(Internally page_pool uses ptr_ring, which is what gives the good
cross CPU performance).

Show adapter(s) (ixgbe2 mlx5p2) statistics (ONLY that changed!)
Ethtool(ixgbe2 ) stat: 732863573 ( 732,863,573) <= tx_bytes /sec
Ethtool(ixgbe2 ) stat: 781724427 ( 781,724,427) <= tx_bytes_nic /sec
Ethtool(ixgbe2 ) stat: 12214393 ( 12,214,393) <= tx_packets /sec
Ethtool(ixgbe2 ) stat: 12214435 ( 12,214,435) <= tx_pkts_nic /sec
Ethtool(mlx5p2 ) stat: 12211786 ( 12,211,786) <= rx3_cache_empty /sec
Ethtool(mlx5p2 ) stat: 36506736 ( 36,506,736) <= rx_64_bytes_phy /sec
Ethtool(mlx5p2 ) stat: 2336430575 ( 2,336,430,575) <= rx_bytes_phy /sec
Ethtool(mlx5p2 ) stat: 12211786 ( 12,211,786) <= rx_cache_empty /sec
Ethtool(mlx5p2 ) stat: 22823073 ( 22,823,073) <= rx_discards_phy /sec
Ethtool(mlx5p2 ) stat: 1471860 ( 1,471,860) <= rx_out_of_buffer /sec
Ethtool(mlx5p2 ) stat: 36506715 ( 36,506,715) <= rx_packets_phy /sec
Ethtool(mlx5p2 ) stat: 2336542282 ( 2,336,542,282) <= rx_prio0_bytes /sec
Ethtool(mlx5p2 ) stat: 13683921 ( 13,683,921) <= rx_prio0_packets /sec
Ethtool(mlx5p2 ) stat: 821015537 ( 821,015,537) <= rx_vport_unicast_bytes /sec
Ethtool(mlx5p2 ) stat: 13683608 ( 13,683,608) <= rx_vport_unicast_packets /sec

Before this patch: single flow performance was 6Mpps, and if I started
two flows the collective performance drop to 4Mpps, because we hit the
page allocator lock (further negative scaling occurs).

V2: Adjustments requested by Tariq
- Changed page_pool_create return codes not return NULL, only
ERR_PTR, as this simplifies err handling in drivers.
- Save a branch in mlx5e_page_release
- Correct page_pool size calc for MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
drivers/net/ethernet/mellanox/mlx5/core/en.h | 3 ++
drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 41 +++++++++++++++++----
drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 16 ++++++--
net/core/page_pool.c | 2 +
4 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
index 28cc26debeda..ab91166f7c5a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
@@ -53,6 +53,8 @@
#include "mlx5_core.h"
#include "en_stats.h"

+struct page_pool;
+
#define MLX5_SET_CFG(p, f, v) MLX5_SET(create_flow_group_in, p, f, v)

#define MLX5E_ETH_HARD_MTU (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN)
@@ -535,6 +537,7 @@ struct mlx5e_rq {
/* XDP */
struct bpf_prog *xdp_prog;
struct mlx5e_xdpsq xdpsq;
+ struct page_pool *page_pool;

/* control */
struct mlx5_wq_ctrl wq_ctrl;
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 2e4ca0f15b62..bf17e6d614d6 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -35,6 +35,7 @@
#include <linux/mlx5/fs.h>
#include <net/vxlan.h>
#include <linux/bpf.h>
+#include <net/page_pool.h>
#include "eswitch.h"
#include "en.h"
#include "en_tc.h"
@@ -387,10 +388,11 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
struct mlx5e_rq_param *rqp,
struct mlx5e_rq *rq)
{
+ struct page_pool_params pp_params = { 0 };
struct mlx5_core_dev *mdev = c->mdev;
void *rqc = rqp->rqc;
void *rqc_wq = MLX5_ADDR_OF(rqc, rqc, wq);
- u32 byte_count;
+ u32 byte_count, pool_size;
int npages;
int wq_sz;
int err;
@@ -429,10 +431,13 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,

rq->buff.map_dir = rq->xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
rq->buff.headroom = params->rq_headroom;
+ pool_size = 1 << params->log_rq_size;

switch (rq->wq_type) {
case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ:

+ pool_size = pool_size * MLX5_MPWRQ_PAGES_PER_WQE;
+
rq->post_wqes = mlx5e_post_rx_mpwqes;
rq->dealloc_wqe = mlx5e_dealloc_rx_mpwqe;

@@ -506,13 +511,31 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
rq->mkey_be = c->mkey_be;
}

- /* This must only be activate for order-0 pages */
- if (rq->xdp_prog) {
- err = xdp_rxq_info_reg_mem_model(&rq->xdp_rxq,
- MEM_TYPE_PAGE_ORDER0, NULL);
- if (err)
- goto err_rq_wq_destroy;
+ /* Create a page_pool and register it with rxq */
+ pp_params.size = PAGE_POOL_PARAMS_SIZE;
+ pp_params.order = rq->buff.page_order;
+ pp_params.dev = c->pdev;
+ pp_params.nid = cpu_to_node(c->cpu);
+ pp_params.dma_dir = rq->buff.map_dir;
+ pp_params.pool_size = pool_size;
+ pp_params.flags = 0; /* No-internal DMA mapping in page_pool */
+
+ /* page_pool can be used even when there is no rq->xdp_prog,
+ * given page_pool does not handle DMA mapping there is no
+ * required state to clear. And page_pool gracefully handle
+ * elevated refcnt.
+ */
+ rq->page_pool = page_pool_create(&pp_params);
+ if (IS_ERR(rq->page_pool)) {
+ kfree(rq->wqe.frag_info);
+ err = PTR_ERR(rq->page_pool);
+ rq->page_pool = NULL;
+ goto err_rq_wq_destroy;
}
+ err = xdp_rxq_info_reg_mem_model(&rq->xdp_rxq,
+ MEM_TYPE_PAGE_POOL, rq->page_pool);
+ if (err)
+ goto err_rq_wq_destroy;

for (i = 0; i < wq_sz; i++) {
struct mlx5e_rx_wqe *wqe = mlx5_wq_ll_get_wqe(&rq->wq, i);
@@ -550,6 +573,8 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
if (rq->xdp_prog)
bpf_prog_put(rq->xdp_prog);
xdp_rxq_info_unreg(&rq->xdp_rxq);
+ if (rq->page_pool)
+ page_pool_destroy_rcu(rq->page_pool);
mlx5_wq_destroy(&rq->wq_ctrl);

return err;
@@ -563,6 +588,8 @@ static void mlx5e_free_rq(struct mlx5e_rq *rq)
bpf_prog_put(rq->xdp_prog);

xdp_rxq_info_unreg(&rq->xdp_rxq);
+ if (rq->page_pool)
+ page_pool_destroy_rcu(rq->page_pool);

switch (rq->wq_type) {
case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ:
diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 6dcc3e8fbd3e..2ac78b88fc3d 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -37,6 +37,7 @@
#include <linux/bpf_trace.h>
#include <net/busy_poll.h>
#include <net/ip6_checksum.h>
+#include <net/page_pool.h>
#include "en.h"
#include "en_tc.h"
#include "eswitch.h"
@@ -221,7 +222,7 @@ static inline int mlx5e_page_alloc_mapped(struct mlx5e_rq *rq,
if (mlx5e_rx_cache_get(rq, dma_info))
return 0;

- dma_info->page = dev_alloc_pages(rq->buff.page_order);
+ dma_info->page = page_pool_dev_alloc_pages(rq->page_pool);
if (unlikely(!dma_info->page))
return -ENOMEM;

@@ -246,11 +247,16 @@ static inline void mlx5e_page_dma_unmap(struct mlx5e_rq *rq,
void mlx5e_page_release(struct mlx5e_rq *rq, struct mlx5e_dma_info *dma_info,
bool recycle)
{
- if (likely(recycle) && mlx5e_rx_cache_put(rq, dma_info))
- return;
+ if (likely(recycle)) {
+ if (mlx5e_rx_cache_put(rq, dma_info))
+ return;

- mlx5e_page_dma_unmap(rq, dma_info);
- put_page(dma_info->page);
+ mlx5e_page_dma_unmap(rq, dma_info);
+ page_pool_recycle_direct(rq->page_pool, dma_info->page);
+ } else {
+ mlx5e_page_dma_unmap(rq, dma_info);
+ put_page(dma_info->page);
+ }
}

static inline bool mlx5e_page_reuse(struct mlx5e_rq *rq,
diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 8bf84d2a6a60..9706ff78a4c9 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -78,7 +78,7 @@ struct page_pool *page_pool_create(const struct page_pool_params *params)

if (params->size < offsetof(struct page_pool_params, nid)) {
WARN(1, "Fix page_pool_params->size code\n");
- return NULL;
+ return ERR_PTR(-EBADR);
}

pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);