Date:   Fri, 21 Jan 2022 13:54:47 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        netdev@...r.kernel.org, magnus.karlsson@...el.com
Subject: Re: [PATCH bpf-next v3 6/7] ice: xsk: improve AF_XDP ZC Tx and use batching API

From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Date: Fri, 21 Jan 2022 13:00:10 +0100

> Apply the logic that was done for regular XDP from commit 9610bd988df9
> ("ice: optimize XDP_TX workloads") to the ZC side of the driver. On top
> of that, introduce batching to Tx that is inspired by i40e's
> implementation with adjustments to the cleaning logic - take into the
> account NAPI budget in ice_clean_xdp_irq_zc().
> 
> Separating the stats structs onto separate cache lines seemed to improve
> the performance.
> 
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---
>  drivers/net/ethernet/intel/ice/ice_txrx.c |   2 +-
>  drivers/net/ethernet/intel/ice/ice_txrx.h |   2 +-
>  drivers/net/ethernet/intel/ice/ice_xsk.c  | 256 ++++++++++++++--------
>  drivers/net/ethernet/intel/ice/ice_xsk.h  |  27 ++-
>  4 files changed, 186 insertions(+), 101 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> index bfb9158b10a4..7ab8c700c884 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> @@ -1463,7 +1463,7 @@ int ice_napi_poll(struct napi_struct *napi, int budget)
>  		bool wd;
>  
>  		if (tx_ring->xsk_pool)
> -			wd = ice_clean_tx_irq_zc(tx_ring, budget);
> +			wd = ice_xmit_zc(tx_ring, ICE_DESC_UNUSED(tx_ring), budget);
>  		else if (ice_ring_is_xdp(tx_ring))
>  			wd = true;
>  		else
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.h b/drivers/net/ethernet/intel/ice/ice_txrx.h
> index 09c8ad2f7403..191f9b8c50ee 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.h
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.h
> @@ -322,9 +322,9 @@ struct ice_tx_ring {
>  	u16 count;			/* Number of descriptors */
>  	u16 q_index;			/* Queue number of ring */
>  	/* stats structs */
> +	struct ice_txq_stats tx_stats;
>  	struct ice_q_stats	stats;
>  	struct u64_stats_sync syncp;
> -	struct ice_txq_stats tx_stats;
>  
>  	/* CL3 - 3rd cacheline starts here */
>  	struct rcu_head rcu;		/* to avoid race on free */
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.c b/drivers/net/ethernet/intel/ice/ice_xsk.c
> index 0463fc594d08..4b6e54f75af6 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.c
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.c
> @@ -671,134 +671,208 @@ int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget)
>  }
>  
>  /**
> - * ice_xmit_zc - Completes AF_XDP entries, and cleans XDP entries
> + * ice_clean_xdp_tx_buf - Free and unmap XDP Tx buffer
>   * @xdp_ring: XDP Tx ring
> - * @budget: max number of frames to xmit
> - *
> - * Returns true if cleanup/transmission is done.
> + * @tx_buf: Tx buffer to clean
>   */
> -static bool ice_xmit_zc(struct ice_tx_ring *xdp_ring, int budget)
> +static void
> +ice_clean_xdp_tx_buf(struct ice_tx_ring *xdp_ring, struct ice_tx_buf *tx_buf)
>  {
> -	struct ice_tx_desc *tx_desc = NULL;
> -	bool work_done = true;
> -	struct xdp_desc desc;
> -	dma_addr_t dma;
> -
> -	while (likely(budget-- > 0)) {
> -		struct ice_tx_buf *tx_buf;
> -
> -		if (unlikely(!ICE_DESC_UNUSED(xdp_ring))) {
> -			xdp_ring->tx_stats.tx_busy++;
> -			work_done = false;
> -			break;
> -		}
> +	xdp_return_frame((struct xdp_frame *)tx_buf->raw_buf);
> +	dma_unmap_single(xdp_ring->dev, dma_unmap_addr(tx_buf, dma),
> +			 dma_unmap_len(tx_buf, len), DMA_TO_DEVICE);
> +	dma_unmap_len_set(tx_buf, len, 0);
> +}
>  
> -		tx_buf = &xdp_ring->tx_buf[xdp_ring->next_to_use];
> +/**
> + * ice_clean_xdp_irq_zc - Reclaim resources after transmit completes on XDP ring
> + * @xdp_ring: XDP ring to clean
> + * @napi_budget: amount of descriptors that NAPI allows us to clean
> + *
> + * Returns count of cleaned descriptors
> + */
> +static u16 ice_clean_xdp_irq_zc(struct ice_tx_ring *xdp_ring, int napi_budget)
> +{
> +	u16 tx_thresh = xdp_ring->tx_thresh;
> +	int budget = napi_budget / tx_thresh;
> +	u16 ntc = xdp_ring->next_to_clean;
> +	struct ice_tx_desc *next_dd_desc;

@next_dd_desc is used only inside the `do { } while`, can be moved
there the reduce the scope.

> +	u16 next_dd = xdp_ring->next_dd;
> +	u16 desc_cnt = xdp_ring->count;
> +	struct ice_tx_buf *tx_buf;
> +	u16 cleared_dds = 0;
> +	u32 xsk_frames = 0;
> +	u16 i;

Same with these 5, from @desc_cnt to @i.

>  
> -		if (!xsk_tx_peek_desc(xdp_ring->xsk_pool, &desc))
> +	do {
> +		next_dd_desc = ICE_TX_DESC(xdp_ring, next_dd);
> +		if (!(next_dd_desc->cmd_type_offset_bsz &
> +		    cpu_to_le64(ICE_TX_DESC_DTYPE_DESC_DONE)))
>  			break;
>  
> -		dma = xsk_buff_raw_get_dma(xdp_ring->xsk_pool, desc.addr);
> -		xsk_buff_raw_dma_sync_for_device(xdp_ring->xsk_pool, dma,
> -						 desc.len);
> +		cleared_dds++;
> +		xsk_frames = 0;
>  
> -		tx_buf->bytecount = desc.len;
> +		for (i = 0; i < tx_thresh; i++) {
> +			tx_buf = &xdp_ring->tx_buf[ntc];
>  
> -		tx_desc = ICE_TX_DESC(xdp_ring, xdp_ring->next_to_use);
> -		tx_desc->buf_addr = cpu_to_le64(dma);
> -		tx_desc->cmd_type_offset_bsz =
> -			ice_build_ctob(ICE_TXD_LAST_DESC_CMD, 0, desc.len, 0);
> +			if (tx_buf->raw_buf) {
> +				ice_clean_xdp_tx_buf(xdp_ring, tx_buf);
> +				tx_buf->raw_buf = NULL;
> +			} else {
> +				xsk_frames++;
> +			}
>  
> -		xdp_ring->next_to_use++;
> -		if (xdp_ring->next_to_use == xdp_ring->count)
> -			xdp_ring->next_to_use = 0;
> -	}
> +			ntc++;
> +			if (ntc >= xdp_ring->count)
> +				ntc = 0;
> +		}
> +		if (xsk_frames)
> +			xsk_tx_completed(xdp_ring->xsk_pool, xsk_frames);
> +		next_dd_desc->cmd_type_offset_bsz = 0;
> +		next_dd = next_dd + tx_thresh;
> +		if (next_dd >= desc_cnt)
> +			next_dd = tx_thresh - 1;
> +	} while (budget--);
>  
> -	if (tx_desc) {
> -		ice_xdp_ring_update_tail(xdp_ring);
> -		xsk_tx_release(xdp_ring->xsk_pool);
> -	}
> +	xdp_ring->next_to_clean = ntc;
> +	xdp_ring->next_dd = next_dd;
>  
> -	return budget > 0 && work_done;
> +	return cleared_dds * tx_thresh;
>  }
>  
>  /**
> - * ice_clean_xdp_tx_buf - Free and unmap XDP Tx buffer
> - * @xdp_ring: XDP Tx ring
> - * @tx_buf: Tx buffer to clean
> + * ice_xmit_pkt - produce a single HW Tx descriptor out of AF_XDP descriptor
> + * @xdp_ring: XDP ring to produce the HW Tx descriptor on
> + * @desc: AF_XDP descriptor to pull the DMA address and length from
> + * @total_bytes: bytes accumulator that will be used for stats update
>   */
> -static void
> -ice_clean_xdp_tx_buf(struct ice_tx_ring *xdp_ring, struct ice_tx_buf *tx_buf)
> +static void ice_xmit_pkt(struct ice_tx_ring *xdp_ring, struct xdp_desc *desc,
> +			 unsigned int *total_bytes)
>  {
> -	xdp_return_frame((struct xdp_frame *)tx_buf->raw_buf);
> -	dma_unmap_single(xdp_ring->dev, dma_unmap_addr(tx_buf, dma),
> -			 dma_unmap_len(tx_buf, len), DMA_TO_DEVICE);
> -	dma_unmap_len_set(tx_buf, len, 0);
> +	struct ice_tx_desc *tx_desc;
> +	dma_addr_t dma;
> +
> +	dma = xsk_buff_raw_get_dma(xdp_ring->xsk_pool, desc->addr);
> +	xsk_buff_raw_dma_sync_for_device(xdp_ring->xsk_pool, dma, desc->len);
> +
> +	tx_desc = ICE_TX_DESC(xdp_ring, xdp_ring->next_to_use++);
> +	tx_desc->buf_addr = cpu_to_le64(dma);
> +	tx_desc->cmd_type_offset_bsz = ice_build_ctob(ICE_TX_DESC_CMD_EOP,
> +						      0, desc->len, 0);
> +
> +	*total_bytes += desc->len;
>  }
>  
>  /**
> - * ice_clean_tx_irq_zc - Completes AF_XDP entries, and cleans XDP entries
> - * @xdp_ring: XDP Tx ring
> - * @budget: NAPI budget
> - *
> - * Returns true if cleanup/tranmission is done.
> + * ice_xmit_pkt_batch - produce a batch of HW Tx descriptors out of AF_XDP descriptors
> + * @xdp_ring: XDP ring to produce the HW Tx descriptors on
> + * @descs: AF_XDP descriptors to pull the DMA addresses and lengths from
> + * @total_bytes: bytes accumulator that will be used for stats update
>   */
> -bool ice_clean_tx_irq_zc(struct ice_tx_ring *xdp_ring, int budget)
> +static void ice_xmit_pkt_batch(struct ice_tx_ring *xdp_ring, struct xdp_desc *descs,
> +			       unsigned int *total_bytes)
>  {
> -	int total_packets = 0, total_bytes = 0;
> -	s16 ntc = xdp_ring->next_to_clean;
> +	u16 tx_thresh = xdp_ring->tx_thresh;
> +	u16 ntu = xdp_ring->next_to_use;
>  	struct ice_tx_desc *tx_desc;
> -	struct ice_tx_buf *tx_buf;
> -	u32 xsk_frames = 0;
> -	bool xmit_done;
> +	dma_addr_t dma;

Same with @dma here.

> +	u32 i;
>  
> -	tx_desc = ICE_TX_DESC(xdp_ring, ntc);
> -	tx_buf = &xdp_ring->tx_buf[ntc];
> -	ntc -= xdp_ring->count;
> +	loop_unrolled_for(i = 0; i < PKTS_PER_BATCH; i++) {
> +		dma = xsk_buff_raw_get_dma(xdp_ring->xsk_pool, descs[i].addr);
> +		xsk_buff_raw_dma_sync_for_device(xdp_ring->xsk_pool, dma, descs[i].len);
>  
> -	do {
> -		if (!(tx_desc->cmd_type_offset_bsz &
> -		      cpu_to_le64(ICE_TX_DESC_DTYPE_DESC_DONE)))
> -			break;
> +		tx_desc = ICE_TX_DESC(xdp_ring, ntu++);
> +		tx_desc->buf_addr = cpu_to_le64(dma);
> +		tx_desc->cmd_type_offset_bsz = ice_build_ctob(ICE_TX_DESC_CMD_EOP,
> +							      0, descs[i].len, 0);
>  
> -		total_bytes += tx_buf->bytecount;
> -		total_packets++;
> +		*total_bytes += descs[i].len;
> +	}
>  
> -		if (tx_buf->raw_buf) {
> -			ice_clean_xdp_tx_buf(xdp_ring, tx_buf);
> -			tx_buf->raw_buf = NULL;
> -		} else {
> -			xsk_frames++;
> -		}
> +	xdp_ring->next_to_use = ntu;
>  
> -		tx_desc->cmd_type_offset_bsz = 0;
> -		tx_buf++;
> -		tx_desc++;
> -		ntc++;
> +	if (xdp_ring->next_to_use > xdp_ring->next_rs) {
> +		tx_desc = ICE_TX_DESC(xdp_ring, xdp_ring->next_rs);
> +		tx_desc->cmd_type_offset_bsz |=
> +			cpu_to_le64(ICE_TX_DESC_CMD_RS << ICE_TXD_QW1_CMD_S);
> +		xdp_ring->next_rs += tx_thresh;
> +	}
> +}
>  
> -		if (unlikely(!ntc)) {
> -			ntc -= xdp_ring->count;
> -			tx_buf = xdp_ring->tx_buf;
> -			tx_desc = ICE_TX_DESC(xdp_ring, 0);
> -		}
> +/**
> + * ice_fill_tx_hw_ring - produce the number of Tx descriptors onto ring
> + * @xdp_ring: XDP ring to produce the HW Tx descriptors on
> + * @descs: AF_XDP descriptors to pull the DMA addresses and lengths from
> + * @nb_pkts: count of packets to be send
> + * @total_bytes: bytes accumulator that will be used for stats update
> + */
> +static void ice_fill_tx_hw_ring(struct ice_tx_ring *xdp_ring, struct xdp_desc *descs,
> +				u32 nb_pkts, unsigned int *total_bytes)
> +{
> +	u16 tx_thresh = xdp_ring->tx_thresh;
> +	struct ice_tx_desc *tx_desc;

And @tx_desc as well.

> +	u32 batched, leftover, i;
> +
> +	batched = nb_pkts & ~(PKTS_PER_BATCH - 1);
> +	leftover = nb_pkts & (PKTS_PER_BATCH - 1);
> +	for (i = 0; i < batched; i += PKTS_PER_BATCH)
> +		ice_xmit_pkt_batch(xdp_ring, &descs[i], total_bytes);
> +	for (i = batched; i < batched + leftover; i++)
> +		ice_xmit_pkt(xdp_ring, &descs[i], total_bytes);
> +
> +	if (xdp_ring->next_to_use > xdp_ring->next_rs) {
> +		tx_desc = ICE_TX_DESC(xdp_ring, xdp_ring->next_rs);
> +		tx_desc->cmd_type_offset_bsz |=
> +			cpu_to_le64(ICE_TX_DESC_CMD_RS << ICE_TXD_QW1_CMD_S);
> +		xdp_ring->next_rs += tx_thresh;
> +	}
> +}
>  
> -		prefetch(tx_desc);
> +/**
> + * ice_xmit_zc - take entries from XSK Tx ring and place them onto HW Tx ring
> + * @xdp_ring: XDP ring to produce the HW Tx descriptors on
> + * @budget: number of free descriptors on HW Tx ring that can be used
> + * @napi_budget: amount of descriptors that NAPI allows us to clean
> + *
> + * Returns true if there is no more work that needs to be done, false otherwise
> + */
> +bool ice_xmit_zc(struct ice_tx_ring *xdp_ring, u32 budget, int napi_budget)
> +{
> +	struct xdp_desc *descs = xdp_ring->xsk_pool->tx_descs;
> +	u16 tx_thresh = xdp_ring->tx_thresh;
> +	u32 nb_pkts, nb_processed = 0;
> +	unsigned int total_bytes = 0;
> +	struct ice_tx_desc *tx_desc;

And this @tx_desc.

>  
> -	} while (likely(--budget));
> +	if (budget < tx_thresh)
> +		budget += ice_clean_xdp_irq_zc(xdp_ring, napi_budget);
> +
> +	nb_pkts = xsk_tx_peek_release_desc_batch(xdp_ring->xsk_pool, budget);
> +	if (!nb_pkts)
> +		return true;
> +
> +	if (xdp_ring->next_to_use + nb_pkts >= xdp_ring->count) {
> +		nb_processed = xdp_ring->count - xdp_ring->next_to_use;
> +		ice_fill_tx_hw_ring(xdp_ring, descs, nb_processed, &total_bytes);
> +		tx_desc = ICE_TX_DESC(xdp_ring, xdp_ring->next_rs);
> +		tx_desc->cmd_type_offset_bsz |=
> +			cpu_to_le64(ICE_TX_DESC_CMD_RS << ICE_TXD_QW1_CMD_S);
> +		xdp_ring->next_rs = tx_thresh - 1;
> +		xdp_ring->next_to_use = 0;
> +	}
>  
> -	ntc += xdp_ring->count;
> -	xdp_ring->next_to_clean = ntc;
> +	ice_fill_tx_hw_ring(xdp_ring, &descs[nb_processed], nb_pkts - nb_processed,
> +			    &total_bytes);
>  
> -	if (xsk_frames)
> -		xsk_tx_completed(xdp_ring->xsk_pool, xsk_frames);
> +	ice_xdp_ring_update_tail(xdp_ring);
> +	ice_update_tx_ring_stats(xdp_ring, nb_pkts, total_bytes);
>  
>  	if (xsk_uses_need_wakeup(xdp_ring->xsk_pool))
>  		xsk_set_tx_need_wakeup(xdp_ring->xsk_pool);
>  
> -	ice_update_tx_ring_stats(xdp_ring, total_packets, total_bytes);
> -	xmit_done = ice_xmit_zc(xdp_ring, ICE_DFLT_IRQ_WORK);
> -
> -	return budget > 0 && xmit_done;
> +	return nb_pkts < budget;
>  }
>  
>  /**
> diff --git a/drivers/net/ethernet/intel/ice/ice_xsk.h b/drivers/net/ethernet/intel/ice/ice_xsk.h
> index 4c7bd8e9dfc4..0cbb5793b5b8 100644
> --- a/drivers/net/ethernet/intel/ice/ice_xsk.h
> +++ b/drivers/net/ethernet/intel/ice/ice_xsk.h
> @@ -6,19 +6,37 @@
>  #include "ice_txrx.h"
>  #include "ice.h"
>  
> +#define PKTS_PER_BATCH 8
> +
> +#ifdef __clang__
> +#define loop_unrolled_for _Pragma("clang loop unroll_count(8)") for
> +#elif __GNUC__ >= 4
> +#define loop_unrolled_for _Pragma("GCC unroll 8") for
> +#else
> +#define loop_unrolled_for for
> +#endif
> +
>  struct ice_vsi;
>  
>  #ifdef CONFIG_XDP_SOCKETS
>  int ice_xsk_pool_setup(struct ice_vsi *vsi, struct xsk_buff_pool *pool,
>  		       u16 qid);
>  int ice_clean_rx_irq_zc(struct ice_rx_ring *rx_ring, int budget);
> -bool ice_clean_tx_irq_zc(struct ice_tx_ring *xdp_ring, int budget);
>  int ice_xsk_wakeup(struct net_device *netdev, u32 queue_id, u32 flags);
>  bool ice_alloc_rx_bufs_zc(struct ice_rx_ring *rx_ring, u16 count);
>  bool ice_xsk_any_rx_ring_ena(struct ice_vsi *vsi);
>  void ice_xsk_clean_rx_ring(struct ice_rx_ring *rx_ring);
>  void ice_xsk_clean_xdp_ring(struct ice_tx_ring *xdp_ring);
> +bool ice_xmit_zc(struct ice_tx_ring *xdp_ring, u32 budget, int napi_budget);
>  #else
> +static inline bool
> +ice_xmit_zc(struct ice_tx_ring __always_unused *xdp_ring,
> +	    u32 __always_unused budget,
> +	    int __always_unused napi_budget)
> +{
> +	return false;
> +}
> +
>  static inline int
>  ice_xsk_pool_setup(struct ice_vsi __always_unused *vsi,
>  		   struct xsk_buff_pool __always_unused *pool,
> @@ -34,13 +52,6 @@ ice_clean_rx_irq_zc(struct ice_rx_ring __always_unused *rx_ring,
>  	return 0;
>  }
>  
> -static inline bool
> -ice_clean_tx_irq_zc(struct ice_tx_ring __always_unused *xdp_ring,
> -		    int __always_unused budget)
> -{
> -	return false;
> -}
> -
>  static inline bool
>  ice_alloc_rx_bufs_zc(struct ice_rx_ring __always_unused *rx_ring,
>  		     u16 __always_unused count)
> -- 
> 2.33.1

Thanks,
Al

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