netdev - Re: [PATCH net-next v2 6/6] tsnep: Add XDP socket zero-copy TX support

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Date:   Tue, 18 Apr 2023 10:27:08 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Gerhard Engleder <gerhard@...leder-embedded.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, edumazet@...gle.com,
        bjorn@...nel.org, magnus.karlsson@...el.com,
        maciej.fijalkowski@...el.com, jonathan.lemon@...il.com
Subject: Re: [PATCH net-next v2 6/6] tsnep: Add XDP socket zero-copy TX
 support

On Sat, 2023-04-15 at 16:42 +0200, Gerhard Engleder wrote:
> Send and complete XSK pool frames within TX NAPI context. NAPI context
> is triggered by ndo_xsk_wakeup.
> 
> Test results with A53 1.2GHz:
> 
> xdpsock txonly copy mode:
>                    pps            pkts           1.00
> tx                 284,409        11,398,144
> Two CPUs with 100% and 10% utilization.
> 
> xdpsock txonly zero-copy mode:
>                    pps            pkts           1.00
> tx                 511,929        5,890,368
> Two CPUs with 100% and 1% utilization.
> 
> Packet rate increases and CPU utilization is reduced.
> 
> Signed-off-by: Gerhard Engleder <gerhard@...leder-embedded.com>
> ---
>  drivers/net/ethernet/engleder/tsnep.h      |   2 +
>  drivers/net/ethernet/engleder/tsnep_main.c | 131 +++++++++++++++++++--
>  2 files changed, 123 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/ethernet/engleder/tsnep.h b/drivers/net/ethernet/engleder/tsnep.h
> index d0bea605a1d1..11b29f56aaf9 100644
> --- a/drivers/net/ethernet/engleder/tsnep.h
> +++ b/drivers/net/ethernet/engleder/tsnep.h
> @@ -70,6 +70,7 @@ struct tsnep_tx_entry {
>  	union {
>  		struct sk_buff *skb;
>  		struct xdp_frame *xdpf;
> +		bool zc;
>  	};
>  	size_t len;
>  	DEFINE_DMA_UNMAP_ADDR(dma);
> @@ -88,6 +89,7 @@ struct tsnep_tx {
>  	int read;
>  	u32 owner_counter;
>  	int increment_owner_counter;
> +	struct xsk_buff_pool *xsk_pool;
>  
>  	u32 packets;
>  	u32 bytes;
> diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c
> index 13e5d4438082..de51d0cc8935 100644
> --- a/drivers/net/ethernet/engleder/tsnep_main.c
> +++ b/drivers/net/ethernet/engleder/tsnep_main.c
> @@ -54,6 +54,8 @@
>  #define TSNEP_TX_TYPE_SKB_FRAG	BIT(1)
>  #define TSNEP_TX_TYPE_XDP_TX	BIT(2)
>  #define TSNEP_TX_TYPE_XDP_NDO	BIT(3)
> +#define TSNEP_TX_TYPE_XDP	(TSNEP_TX_TYPE_XDP_TX | TSNEP_TX_TYPE_XDP_NDO)
> +#define TSNEP_TX_TYPE_XSK	BIT(4)
>  
>  #define TSNEP_XDP_TX		BIT(0)
>  #define TSNEP_XDP_REDIRECT	BIT(1)
> @@ -322,13 +324,51 @@ static void tsnep_tx_init(struct tsnep_tx *tx)
>  	tx->increment_owner_counter = TSNEP_RING_SIZE - 1;
>  }
>  
> +static void tsnep_tx_enable(struct tsnep_tx *tx)
> +{
> +	struct netdev_queue *nq;
> +
> +	nq = netdev_get_tx_queue(tx->adapter->netdev, tx->queue_index);
> +
> +	local_bh_disable();
> +	__netif_tx_lock(nq, smp_processor_id());

The above 2 statements could be replaced with:

	__netif_tx_lock_bh()

> +	netif_tx_wake_queue(nq);
> +	__netif_tx_unlock(nq);
> +	local_bh_enable();

__netif_tx_unlock_bh()

> +}
> +
> +static void tsnep_tx_disable(struct tsnep_tx *tx, struct napi_struct *napi)
> +{
> +	struct netdev_queue *nq;
> +	u32 val;
> +
> +	nq = netdev_get_tx_queue(tx->adapter->netdev, tx->queue_index);
> +
> +	local_bh_disable();
> +	__netif_tx_lock(nq, smp_processor_id());

Same here.


Thanks!

Paolo