Re: [PATCH v7] ixgbe: let the xdpdrv work with more than 64 cpus

[Jason Xing]

On Wed, Sep 1, 2021 at 6:12 PM <kerneljasonxing@xxxxxxxxx> wrote:
>
> From: Jason Xing <xingwanli@xxxxxxxxxxxx>
>
> Originally, ixgbe driver doesn't allow the mounting of xdpdrv if the
> server is equipped with more than 64 cpus online. So it turns out that
> the loading of xdpdrv causes the "NOMEM" failure.
>
> Actually, we can adjust the algorithm and then make it work through
> mapping the current cpu to some xdp ring with the protect of @tx_lock.
>
> Here're some numbers before/after applying this patch with xdp-example
> loaded on the eth0X:
>
> As client (tx path):
>                      Before    After
> TCP_STREAM send-64   734.14    714.20
> TCP_STREAM send-128  1401.91   1395.05
> TCP_STREAM send-512  5311.67   5292.84
> TCP_STREAM send-1k   9277.40   9356.22 (not stable)
> TCP_RR     send-1    22559.75  21844.22
> TCP_RR     send-128  23169.54  22725.13
> TCP_RR     send-512  21670.91  21412.56
>
> As server (rx path):
>                      Before    After
> TCP_STREAM send-64   1416.49   1383.12
> TCP_STREAM send-128  3141.49   3055.50
> TCP_STREAM send-512  9488.73   9487.44
> TCP_STREAM send-1k   9491.17   9356.22 (not stable)
> TCP_RR     send-1    23617.74  23601.60
> ...
>
> Notice: the TCP_RR mode is unstable as the official document explaines.
>
> I tested many times with different parameters combined through netperf.
> Though the result is not that accurate, I cannot see much influence on
> this patch. The static key is places on the hot path, but it actually
> shouldn't cause a huge regression theoretically.
>
> Fixes: 33fdc82f08 ("ixgbe: add support for XDP_TX action")
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Co-developed-by: Shujin Li <lishujin@xxxxxxxxxxxx>
> Signed-off-by: Shujin Li <lishujin@xxxxxxxxxxxx>
> Signed-off-by: Jason Xing <xingwanli@xxxxxxxxxxxx>
> ---
> v7:
> - Factorized to a single spin_lock/unlock in ixgbe_xdp_xmit() (Eric)
> - Handle other parts of lock/unlock in ixgbe_run_xdp()/_zc() (Jason)
>

Does this change make any sense? I think it is much clearer than the
v6 patch and they both have the same idea. Now I'm looking for more
advice :-)

Thanks,
Jason

> v6:
> - Move the declaration of static-key to the proper position (Test Robot)
> - Add reported-by tag (Jason)
> - Add more detailed performance test results (Jason)
>
> v5:
> - Change back to nr_cpu_ids (Eric)
>
> v4:
> - Update the wrong commit messages. (Jason)
>
> v3:
> - Change nr_cpu_ids to num_online_cpus() (Maciej)
> - Rename MAX_XDP_QUEUES to IXGBE_MAX_XDP_QS (Maciej)
> - Rename ixgbe_determine_xdp_cpu() to ixgbe_determine_xdp_q_idx() (Maciej)
> - Wrap ixgbe_xdp_ring_update_tail() with lock into one function (Maciej)
>
> v2:
> - Adjust cpu id in ixgbe_xdp_xmit(). (Jesper)
> - Add a fallback path. (Maciej)
> - Adjust other parts related to xdp ring.
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe.h           | 23 +++++++++-
>  drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c       |  9 +++-
>  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c      | 50 ++++++++++++++++------
>  .../net/ethernet/intel/ixgbe/ixgbe_txrx_common.h   |  3 +-
>  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c       | 16 ++++---
>  5 files changed, 77 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> index a604552..4a69823 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> @@ -351,6 +351,7 @@ struct ixgbe_ring {
>         };
>         u16 rx_offset;
>         struct xdp_rxq_info xdp_rxq;
> +       spinlock_t tx_lock;     /* used in XDP mode */
>         struct xsk_buff_pool *xsk_pool;
>         u16 ring_idx;           /* {rx,tx,xdp}_ring back reference idx */
>         u16 rx_buf_len;
> @@ -375,11 +376,13 @@ enum ixgbe_ring_f_enum {
>  #define IXGBE_MAX_FCOE_INDICES         8
>  #define MAX_RX_QUEUES                  (IXGBE_MAX_FDIR_INDICES + 1)
>  #define MAX_TX_QUEUES                  (IXGBE_MAX_FDIR_INDICES + 1)
> -#define MAX_XDP_QUEUES                 (IXGBE_MAX_FDIR_INDICES + 1)
> +#define IXGBE_MAX_XDP_QS               (IXGBE_MAX_FDIR_INDICES + 1)
>  #define IXGBE_MAX_L2A_QUEUES           4
>  #define IXGBE_BAD_L2A_QUEUE            3
>  #define IXGBE_MAX_MACVLANS             63
>
> +DECLARE_STATIC_KEY_FALSE(ixgbe_xdp_locking_key);
> +
>  struct ixgbe_ring_feature {
>         u16 limit;      /* upper limit on feature indices */
>         u16 indices;    /* current value of indices */
> @@ -629,7 +632,7 @@ struct ixgbe_adapter {
>
>         /* XDP */
>         int num_xdp_queues;
> -       struct ixgbe_ring *xdp_ring[MAX_XDP_QUEUES];
> +       struct ixgbe_ring *xdp_ring[IXGBE_MAX_XDP_QS];
>         unsigned long *af_xdp_zc_qps; /* tracks AF_XDP ZC enabled rings */
>
>         /* TX */
> @@ -772,6 +775,22 @@ struct ixgbe_adapter {
>  #endif /* CONFIG_IXGBE_IPSEC */
>  };
>
> +static inline int ixgbe_determine_xdp_q_idx(int cpu)
> +{
> +       if (static_key_enabled(&ixgbe_xdp_locking_key))
> +               return cpu % IXGBE_MAX_XDP_QS;
> +       else
> +               return cpu;
> +}
> +
> +static inline
> +struct ixgbe_ring *ixgbe_determine_xdp_ring(struct ixgbe_adapter *adapter)
> +{
> +       int index = ixgbe_determine_xdp_q_idx(smp_processor_id());
> +
> +       return adapter->xdp_ring[index];
> +}
> +
>  static inline u8 ixgbe_max_rss_indices(struct ixgbe_adapter *adapter)
>  {
>         switch (adapter->hw.mac.type) {
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
> index 0218f6c..86b1116 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
> @@ -299,7 +299,10 @@ static void ixgbe_cache_ring_register(struct ixgbe_adapter *adapter)
>
>  static int ixgbe_xdp_queues(struct ixgbe_adapter *adapter)
>  {
> -       return adapter->xdp_prog ? nr_cpu_ids : 0;
> +       int queues;
> +
> +       queues = min_t(int, IXGBE_MAX_XDP_QS, nr_cpu_ids);
> +       return adapter->xdp_prog ? queues : 0;
>  }
>
>  #define IXGBE_RSS_64Q_MASK     0x3F
> @@ -947,6 +950,7 @@ static int ixgbe_alloc_q_vector(struct ixgbe_adapter *adapter,
>                 ring->count = adapter->tx_ring_count;
>                 ring->queue_index = xdp_idx;
>                 set_ring_xdp(ring);
> +               spin_lock_init(&ring->tx_lock);
>
>                 /* assign ring to adapter */
>                 WRITE_ONCE(adapter->xdp_ring[xdp_idx], ring);
> @@ -1032,6 +1036,9 @@ static void ixgbe_free_q_vector(struct ixgbe_adapter *adapter, int v_idx)
>         adapter->q_vector[v_idx] = NULL;
>         __netif_napi_del(&q_vector->napi);
>
> +       if (static_key_enabled(&ixgbe_xdp_locking_key))
> +               static_branch_dec(&ixgbe_xdp_locking_key);
> +
>         /*
>          * after a call to __netif_napi_del() napi may still be used and
>          * ixgbe_get_stats64() might access the rings on this vector,
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> index 14aea40..8b9e21b 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
> @@ -165,6 +165,9 @@ static int ixgbe_notify_dca(struct notifier_block *, unsigned long event,
>  MODULE_DESCRIPTION("Intel(R) 10 Gigabit PCI Express Network Driver");
>  MODULE_LICENSE("GPL v2");
>
> +DEFINE_STATIC_KEY_FALSE(ixgbe_xdp_locking_key);
> +EXPORT_SYMBOL(ixgbe_xdp_locking_key);
> +
>  static struct workqueue_struct *ixgbe_wq;
>
>  static bool ixgbe_check_cfg_remove(struct ixgbe_hw *hw, struct pci_dev *pdev);
> @@ -2197,6 +2200,7 @@ static struct sk_buff *ixgbe_run_xdp(struct ixgbe_adapter *adapter,
>  {
>         int err, result = IXGBE_XDP_PASS;
>         struct bpf_prog *xdp_prog;
> +       struct ixgbe_ring *ring;
>         struct xdp_frame *xdpf;
>         u32 act;
>
> @@ -2215,7 +2219,12 @@ static struct sk_buff *ixgbe_run_xdp(struct ixgbe_adapter *adapter,
>                 xdpf = xdp_convert_buff_to_frame(xdp);
>                 if (unlikely(!xdpf))
>                         goto out_failure;
> -               result = ixgbe_xmit_xdp_ring(adapter, xdpf);
> +               ring = ixgbe_determine_xdp_ring(adapter);
> +               if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +                       spin_lock(&ring->tx_lock);
> +               result = ixgbe_xmit_xdp_ring(ring, xdpf);
> +               if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +                       spin_unlock(&ring->tx_lock);
>                 if (result == IXGBE_XDP_CONSUMED)
>                         goto out_failure;
>                 break;
> @@ -2422,13 +2431,9 @@ static int ixgbe_clean_rx_irq(struct ixgbe_q_vector *q_vector,
>                 xdp_do_flush_map();
>
>         if (xdp_xmit & IXGBE_XDP_TX) {
> -               struct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()];
> +               struct ixgbe_ring *ring = ixgbe_determine_xdp_ring(adapter);
>
> -               /* Force memory writes to complete before letting h/w
> -                * know there are new descriptors to fetch.
> -                */
> -               wmb();
> -               writel(ring->next_to_use, ring->tail);
> +               ixgbe_xdp_ring_update_tail_locked(ring);
>         }
>
>         u64_stats_update_begin(&rx_ring->syncp);
> @@ -6320,7 +6325,7 @@ static int ixgbe_sw_init(struct ixgbe_adapter *adapter,
>         if (ixgbe_init_rss_key(adapter))
>                 return -ENOMEM;
>
> -       adapter->af_xdp_zc_qps = bitmap_zalloc(MAX_XDP_QUEUES, GFP_KERNEL);
> +       adapter->af_xdp_zc_qps = bitmap_zalloc(IXGBE_MAX_XDP_QS, GFP_KERNEL);
>         if (!adapter->af_xdp_zc_qps)
>                 return -ENOMEM;
>
> @@ -8536,10 +8541,9 @@ static u16 ixgbe_select_queue(struct net_device *dev, struct sk_buff *skb,
>  }
>
>  #endif
> -int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,
> +int ixgbe_xmit_xdp_ring(struct ixgbe_ring *ring,
>                         struct xdp_frame *xdpf)
>  {
> -       struct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()];
>         struct ixgbe_tx_buffer *tx_buffer;
>         union ixgbe_adv_tx_desc *tx_desc;
>         u32 len, cmd_type;
> @@ -10130,8 +10134,13 @@ static int ixgbe_xdp_setup(struct net_device *dev, struct bpf_prog *prog)
>                         return -EINVAL;
>         }
>
> -       if (nr_cpu_ids > MAX_XDP_QUEUES)
> +       /* if the number of cpus is much larger than the maximum of queues,
> +        * we should stop it and then return with NOMEM like before.
> +        */
> +       if (nr_cpu_ids > IXGBE_MAX_XDP_QS * 2)
>                 return -ENOMEM;
> +       else if (nr_cpu_ids > IXGBE_MAX_XDP_QS)
> +               static_branch_inc(&ixgbe_xdp_locking_key);
>
>         old_prog = xchg(&adapter->xdp_prog, prog);
>         need_reset = (!!prog != !!old_prog);
> @@ -10195,6 +10204,15 @@ void ixgbe_xdp_ring_update_tail(struct ixgbe_ring *ring)
>         writel(ring->next_to_use, ring->tail);
>  }
>
> +void ixgbe_xdp_ring_update_tail_locked(struct ixgbe_ring *ring)
> +{
> +       if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +               spin_lock(&ring->tx_lock);
> +       ixgbe_xdp_ring_update_tail(ring);
> +       if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +               spin_unlock(&ring->tx_lock);
> +}
> +
>  static int ixgbe_xdp_xmit(struct net_device *dev, int n,
>                           struct xdp_frame **frames, u32 flags)
>  {
> @@ -10212,18 +10230,21 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
>         /* During program transitions its possible adapter->xdp_prog is assigned
>          * but ring has not been configured yet. In this case simply abort xmit.
>          */
> -       ring = adapter->xdp_prog ? adapter->xdp_ring[smp_processor_id()] : NULL;
> +       ring = adapter->xdp_prog ? ixgbe_determine_xdp_ring(adapter) : NULL;
>         if (unlikely(!ring))
>                 return -ENXIO;
>
>         if (unlikely(test_bit(__IXGBE_TX_DISABLED, &ring->state)))
>                 return -ENXIO;
>
> +       if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +               spin_lock(&ring->tx_lock);
> +
>         for (i = 0; i < n; i++) {
>                 struct xdp_frame *xdpf = frames[i];
>                 int err;
>
> -               err = ixgbe_xmit_xdp_ring(adapter, xdpf);
> +               err = ixgbe_xmit_xdp_ring(ring, xdpf);
>                 if (err != IXGBE_XDP_TX)
>                         break;
>                 nxmit++;
> @@ -10232,6 +10253,9 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
>         if (unlikely(flags & XDP_XMIT_FLUSH))
>                 ixgbe_xdp_ring_update_tail(ring);
>
> +       if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +               spin_unlock(&ring->tx_lock);
> +
>         return nxmit;
>  }
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_txrx_common.h b/drivers/net/ethernet/intel/ixgbe/ixgbe_txrx_common.h
> index 2aeec78..a82533f 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_txrx_common.h
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_txrx_common.h
> @@ -12,7 +12,7 @@
>  #define IXGBE_TXD_CMD (IXGBE_TXD_CMD_EOP | \
>                        IXGBE_TXD_CMD_RS)
>
> -int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,
> +int ixgbe_xmit_xdp_ring(struct ixgbe_ring *ring,
>                         struct xdp_frame *xdpf);
>  bool ixgbe_cleanup_headers(struct ixgbe_ring *rx_ring,
>                            union ixgbe_adv_rx_desc *rx_desc,
> @@ -23,6 +23,7 @@ void ixgbe_process_skb_fields(struct ixgbe_ring *rx_ring,
>  void ixgbe_rx_skb(struct ixgbe_q_vector *q_vector,
>                   struct sk_buff *skb);
>  void ixgbe_xdp_ring_update_tail(struct ixgbe_ring *ring);
> +void ixgbe_xdp_ring_update_tail_locked(struct ixgbe_ring *ring);
>  void ixgbe_irq_rearm_queues(struct ixgbe_adapter *adapter, u64 qmask);
>
>  void ixgbe_txrx_ring_disable(struct ixgbe_adapter *adapter, int ring);
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> index b1d22e4..db2bc58 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> @@ -100,6 +100,7 @@ static int ixgbe_run_xdp_zc(struct ixgbe_adapter *adapter,
>  {
>         int err, result = IXGBE_XDP_PASS;
>         struct bpf_prog *xdp_prog;
> +       struct ixgbe_ring *ring;
>         struct xdp_frame *xdpf;
>         u32 act;
>
> @@ -120,7 +121,12 @@ static int ixgbe_run_xdp_zc(struct ixgbe_adapter *adapter,
>                 xdpf = xdp_convert_buff_to_frame(xdp);
>                 if (unlikely(!xdpf))
>                         goto out_failure;
> -               result = ixgbe_xmit_xdp_ring(adapter, xdpf);
> +               ring = ixgbe_determine_xdp_ring(adapter);
> +               if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +                       spin_lock(&ring->tx_lock);
> +               result = ixgbe_xmit_xdp_ring(ring, xdpf);
> +               if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> +                       spin_unlock(&ring->tx_lock);
>                 if (result == IXGBE_XDP_CONSUMED)
>                         goto out_failure;
>                 break;
> @@ -334,13 +340,9 @@ int ixgbe_clean_rx_irq_zc(struct ixgbe_q_vector *q_vector,
>                 xdp_do_flush_map();
>
>         if (xdp_xmit & IXGBE_XDP_TX) {
> -               struct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()];
> +               struct ixgbe_ring *ring = ixgbe_determine_xdp_ring(adapter);
>
> -               /* Force memory writes to complete before letting h/w
> -                * know there are new descriptors to fetch.
> -                */
> -               wmb();
> -               writel(ring->next_to_use, ring->tail);
> +               ixgbe_xdp_ring_update_tail_locked(ring);
>         }
>
>         u64_stats_update_begin(&rx_ring->syncp);
> --
> 1.8.3.1
>