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Date: Wed, 4 Apr 2018 16:12:14 +0300
From: Tariq Toukan <tariqt@...lanox.com>
To: Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
BjörnTöpel <bjorn.topel@...el.com>,
magnus.karlsson@...el.com
Cc: eugenia@...lanox.com, Jason Wang <jasowang@...hat.com>,
John Fastabend <john.fastabend@...il.com>,
Eran Ben Elisha <eranbe@...lanox.com>,
Saeed Mahameed <saeedm@...lanox.com>, galp@...lanox.com,
Daniel Borkmann <borkmann@...earbox.net>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
Tariq Toukan <tariqt@...lanox.com>
Subject: Re: [net-next V9 PATCH 14/16] mlx5: use page_pool for
xdp_return_frame call
On 03/04/2018 2:08 PM, Jesper Dangaard Brouer wrote:
> 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 returns the page through the page allocator. And at the
> same time, have pages getting returned to the page_pool from
> ndp_xdp_xmit DMA completion.
>
> The performance improvement for XDP_REDIRECT in this patch is really
> good. Especially considering that (currently) the xdp_return_frame
> API and page_pool_put_page() does per frame operations of both
> rhashtable ID-lookup and locked return into (page_pool) ptr_ring.
> (It is the plan to remove these per frame operation in a followup
> patchset).
>
> The benchmark performed was RX on mlx5 and XDP_REDIRECT out ixgbe,
> with xdp_redirect_map (using devmap) . And the target/maximum
> capability of ixgbe is 13Mpps (on this HW setup).
>
> Before this patch for mlx5, XDP redirected frames were returned via
> the page allocator. The 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).
>
> Two test scenarios need to be covered, for xdp_return_frame API, which
> is DMA-TX completion running on same-CPU or cross-CPU free/return.
> Results were same-CPU=10Mpps, and cross-CPU=12Mpps. This is very
> close to our 13Mpps max target.
>
> The reason max target isn't reached in cross-CPU test, is likely due
> to RX-ring DMA unmap/map overhead (which doesn't occur in ixgbe to
> ixgbe testing). It is also planned to remove this unnecessary DMA
> unmap in a later patchset
>
> 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
>
> V5: Updated patch desc
>
> V8: Adjust for b0cedc844c00 ("net/mlx5e: Remove rq_headroom field from params")
> V9:
> - Adjust for 121e89275471 ("net/mlx5e: Refactor RQ XDP_TX indication")
> - Adjust for 73281b78a37a ("net/mlx5e: Derive Striding RQ size from MTU")
> - Correct handling if page_pool_create fail for MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
> Reviewed-by: Tariq Toukan <tariqt@...lanox.com>
> Acked-by: Saeed Mahameed <saeedm@...lanox.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 ++++++--
> 3 files changed, 48 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> index 1a05d1072c5e..3317a4da87cb 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)
> @@ -534,6 +536,7 @@ struct mlx5e_rq {
> unsigned int hw_mtu;
> struct mlx5e_xdpsq xdpsq;
> DECLARE_BITMAP(flags, 8);
> + 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 13c1e61258a7..d0f2cd86ef32 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"
> @@ -389,10 +390,11 @@ 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;
> @@ -432,9 +434,12 @@ static int mlx5e_alloc_rq(struct mlx5e_channel *c,
>
> rq->buff.map_dir = rq->xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
> rq->buff.headroom = mlx5e_get_rq_headroom(mdev, params);
> + pool_size = 1 << params->log_rq_mtu_frames;
>
> switch (rq->wq_type) {
> case MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ:
> +
> + pool_size = pool_size * MLX5_MPWRQ_PAGES_PER_WQE;
For rq->wq_type != MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ, please use:
pool_size = 1 << params->log_rq_mtu_frames;
For rq->wq_type == MLX5_WQ_TYPE_LINKED_LIST_STRIDING_RQ, please use:
pool_size = MLX5_MPWRQ_PAGES_PER_WQ * mlx5e_mpwqe_get_log_rq_size(params);
Thanks,
Tariq
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