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Message-ID: <CAL+tcoADu-ZZewsZzGDaL7NugxFTWO_Q+7WsLHs3Mx-XHjJnyg@mail.gmail.com>
Date: Fri, 25 Jul 2025 20:11:18 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Larysa Zaremba <larysa.zaremba@...el.com>
Cc: anthony.l.nguyen@...el.com, przemyslaw.kitszel@...el.com, 
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, bjorn@...nel.org, 
	magnus.karlsson@...el.com, maciej.fijalkowski@...el.com, 
	jonathan.lemon@...il.com, sdf@...ichev.me, ast@...nel.org, 
	daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com, 
	bpf@...r.kernel.org, intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next 4/5] ixgbe: xsk: support batched xsk Tx
 interfaces to increase performance

On Fri, Jul 25, 2025 at 6:52 PM Larysa Zaremba <larysa.zaremba@...el.com> wrote:
>
> On Sun, Jul 20, 2025 at 05:11:22PM +0800, Jason Xing wrote:
> > From: Jason Xing <kernelxing@...cent.com>
> >
> > Like what i40e driver initially did in commit 3106c580fb7cf
> > ("i40e: Use batched xsk Tx interfaces to increase performance"), use
> > the batched xsk feature to transmit packets.
> >
> > Signed-off-by: Jason Xing <kernelxing@...cent.com>
> > ---
> >  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 106 +++++++++++++------
> >  1 file changed, 72 insertions(+), 34 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> > index f3d3f5c1cdc7..9fe2c4bf8bc5 100644
> > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> > @@ -2,12 +2,15 @@
> >  /* Copyright(c) 2018 Intel Corporation. */
> >
> >  #include <linux/bpf_trace.h>
> > +#include <linux/unroll.h>
> >  #include <net/xdp_sock_drv.h>
> >  #include <net/xdp.h>
> >
> >  #include "ixgbe.h"
> >  #include "ixgbe_txrx_common.h"
> >
> > +#define PKTS_PER_BATCH 4
> > +
> >  struct xsk_buff_pool *ixgbe_xsk_pool(struct ixgbe_adapter *adapter,
> >                                    struct ixgbe_ring *ring)
> >  {
> > @@ -388,58 +391,93 @@ void ixgbe_xsk_clean_rx_ring(struct ixgbe_ring *rx_ring)
> >       }
> >  }
> >
> > -static bool ixgbe_xmit_zc(struct ixgbe_ring *xdp_ring, unsigned int budget)
> > +static void ixgbe_set_rs_bit(struct ixgbe_ring *xdp_ring)
> > +{
> > +     u16 ntu = xdp_ring->next_to_use ? xdp_ring->next_to_use - 1 : xdp_ring->count - 1;
> > +     union ixgbe_adv_tx_desc *tx_desc;
> > +
> > +     tx_desc = IXGBE_TX_DESC(xdp_ring, ntu);
> > +     tx_desc->read.cmd_type_len |= cpu_to_le32(IXGBE_TXD_CMD_RS);
> > +}
> > +
> > +static void ixgbe_xmit_pkt(struct ixgbe_ring *xdp_ring, struct xdp_desc *desc,
> > +                        int i)
> > +
>
> `i` parameter seems redundant here, why not just pass desc + i as a parameter?

Let me resolve this :)

Thanks,
Jason

>
> >  {
> >       struct xsk_buff_pool *pool = xdp_ring->xsk_pool;
> >       union ixgbe_adv_tx_desc *tx_desc = NULL;
> >       struct ixgbe_tx_buffer *tx_bi;
> > -     struct xdp_desc desc;
> >       dma_addr_t dma;
> >       u32 cmd_type;
> >
> > -     if (!budget)
> > -             return true;
> > +     dma = xsk_buff_raw_get_dma(pool, desc[i].addr);
> > +     xsk_buff_raw_dma_sync_for_device(pool, dma, desc[i].len);
> >
> > -     while (likely(budget)) {
> > -             if (!netif_carrier_ok(xdp_ring->netdev))
> > -                     break;
> > +     tx_bi = &xdp_ring->tx_buffer_info[xdp_ring->next_to_use];
> > +     tx_bi->bytecount = desc[i].len;
> > +     tx_bi->xdpf = NULL;
> > +     tx_bi->gso_segs = 1;
> >
> > -             if (!xsk_tx_peek_desc(pool, &desc))
> > -                     break;
> > +     tx_desc = IXGBE_TX_DESC(xdp_ring, xdp_ring->next_to_use);
> > +     tx_desc->read.buffer_addr = cpu_to_le64(dma);
> >
> > -             dma = xsk_buff_raw_get_dma(pool, desc.addr);
> > -             xsk_buff_raw_dma_sync_for_device(pool, dma, desc.len);
> > +     cmd_type = IXGBE_ADVTXD_DTYP_DATA |
> > +                IXGBE_ADVTXD_DCMD_DEXT |
> > +                IXGBE_ADVTXD_DCMD_IFCS;
> > +     cmd_type |= desc[i].len | IXGBE_TXD_CMD_EOP;
> > +     tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
> > +     tx_desc->read.olinfo_status =
> > +             cpu_to_le32(desc[i].len << IXGBE_ADVTXD_PAYLEN_SHIFT);
> >
> > -             tx_bi = &xdp_ring->tx_buffer_info[xdp_ring->next_to_use];
> > -             tx_bi->bytecount = desc.len;
> > -             tx_bi->xdpf = NULL;
> > -             tx_bi->gso_segs = 1;
> > +     xdp_ring->next_to_use++;
> > +}
> >
> > -             tx_desc = IXGBE_TX_DESC(xdp_ring, xdp_ring->next_to_use);
> > -             tx_desc->read.buffer_addr = cpu_to_le64(dma);
> > +static void ixgbe_xmit_pkt_batch(struct ixgbe_ring *xdp_ring, struct xdp_desc *desc)
> > +{
> > +     u32 i;
> >
> > -             /* put descriptor type bits */
> > -             cmd_type = IXGBE_ADVTXD_DTYP_DATA |
> > -                        IXGBE_ADVTXD_DCMD_DEXT |
> > -                        IXGBE_ADVTXD_DCMD_IFCS;
> > -             cmd_type |= desc.len | IXGBE_TXD_CMD;
> > -             tx_desc->read.cmd_type_len = cpu_to_le32(cmd_type);
> > -             tx_desc->read.olinfo_status =
> > -                     cpu_to_le32(desc.len << IXGBE_ADVTXD_PAYLEN_SHIFT);
> > +     unrolled_count(PKTS_PER_BATCH)
> > +     for (i = 0; i < PKTS_PER_BATCH; i++)
> > +             ixgbe_xmit_pkt(xdp_ring, desc, i);
> > +}
> >
> > -             xdp_ring->next_to_use++;
> > -             if (xdp_ring->next_to_use == xdp_ring->count)
> > -                     xdp_ring->next_to_use = 0;
> > +static void ixgbe_fill_tx_hw_ring(struct ixgbe_ring *xdp_ring,
> > +                               struct xdp_desc *descs, u32 nb_pkts)
> > +{
> > +     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)
> > +             ixgbe_xmit_pkt_batch(xdp_ring, &descs[i]);
> > +     for (i = batched; i < batched + leftover; i++)
> > +             ixgbe_xmit_pkt(xdp_ring, &descs[i], 0);
> > +}
> >
> > -             budget--;
> > -     }
> > +static bool ixgbe_xmit_zc(struct ixgbe_ring *xdp_ring, unsigned int budget)
> > +{
> > +     struct xdp_desc *descs = xdp_ring->xsk_pool->tx_descs;
> > +     u32 nb_pkts, nb_processed = 0;
> >
> > -     if (tx_desc) {
> > -             ixgbe_xdp_ring_update_tail(xdp_ring);
> > -             xsk_tx_release(pool);
> > +     if (!netif_carrier_ok(xdp_ring->netdev))
> > +             return true;
> > +
> > +     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;
> > +             ixgbe_fill_tx_hw_ring(xdp_ring, descs, nb_processed);
> > +             xdp_ring->next_to_use = 0;
> >       }
> >
> > -     return !!budget;
> > +     ixgbe_fill_tx_hw_ring(xdp_ring, &descs[nb_processed], nb_pkts - nb_processed);
> > +
> > +     ixgbe_set_rs_bit(xdp_ring);
> > +     ixgbe_xdp_ring_update_tail(xdp_ring);
> > +
> > +     return nb_pkts < budget;
> >  }
> >
> >  static void ixgbe_clean_xdp_tx_buffer(struct ixgbe_ring *tx_ring,
> > --
> > 2.41.3
> >
> >

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