On Thu, Aug 26, 2021 at 5:07 PM Maciej Fijalkowski
<maciej.fijalkowski@xxxxxxxxx> wrote:
>
> On Wed, Aug 25, 2021 at 08:02:41PM +0800, 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.
> >
> > Considering the performance of xdpdrv mode, I add another limit like ice
> > driver where the number of cpus should be within the twice of
> > MAX_XDP_QUEUES.
>
> Have you measured the impact on perf that this patch yields? On ice XDP
> ring pointers are propagated to Rx ring on setup path whereas you
> currently retrieve it per each xmitted frame.
>
Not yet. I have not found the proper environment to test the real
performance with different cases. At first, I thought this patch could
map different cpus to the same queues with the @tx_lock which would do
harm to the performance to some extent.
I decided to get rid of this description.
> >
> > v2:
> > - Adjust cpu id in ixgbe_xdp_xmit(). (Jesper)
> > - Add a fallback path. (Maciej)
> > - Adjust other parts related to xdp ring.
> >
> > Fixes: 33fdc82f08 ("ixgbe: add support for XDP_TX action")
> > Co-developed-by: Shujin Li <lishujin@xxxxxxxxxxxx>
> > Signed-off-by: Shujin Li <lishujin@xxxxxxxxxxxx>
> > Signed-off-by: Jason Xing <xingwanli@xxxxxxxxxxxx>
> > ---
> > drivers/net/ethernet/intel/ixgbe/ixgbe.h | 11 +++++
> > drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c | 6 ++-
> > drivers/net/ethernet/intel/ixgbe/ixgbe_main.c | 63 ++++++++++++++++++++-------
> > drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 15 ++++---
> > 4 files changed, 72 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe.h b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> > index a604552..466b2b0 100644
> > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe.h
> > @@ -82,6 +82,8 @@
> > #define IXGBE_2K_TOO_SMALL_WITH_PADDING \
> > ((NET_SKB_PAD + IXGBE_RXBUFFER_1536) > SKB_WITH_OVERHEAD(IXGBE_RXBUFFER_2K))
> >
> > +DECLARE_STATIC_KEY_FALSE(ixgbe_xdp_locking_key);
> > +
> > static inline int ixgbe_compute_pad(int rx_buf_len)
> > {
> > int page_size, pad_size;
> > @@ -351,6 +353,7 @@ 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;
> > @@ -772,6 +775,14 @@ struct ixgbe_adapter {
> > #endif /* CONFIG_IXGBE_IPSEC */
> > };
> >
> > +static inline int ixgbe_determine_xdp_cpu(int cpu)
> > +{
> > + if (static_key_enabled(&ixgbe_xdp_locking_key))
> > + return cpu % MAX_XDP_QUEUES;
> > + else
> > + return cpu;
> > +}
> > +
> > 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..d6b58e1 100644
> > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
> > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c
> > @@ -299,7 +299,7 @@ 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;
> > + return adapter->xdp_prog ? min_t(int, MAX_XDP_QUEUES, nr_cpu_ids) : 0;
>
> AFAIK nr_cpu_ids will give you the max possible cpus on the underlying
> system, maybe we should stick to num_online_cpus() instead?
>
Sure, I'll do that change. Maybe we should also stick to
num_online_cpus() in the function ixgbe_xdp_setup()?
> > }
> >
> > #define IXGBE_RSS_64Q_MASK 0x3F
> > @@ -947,6 +947,7 @@ 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 +1033,9 @@ 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..4c94577 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);
> > @@ -2422,13 +2425,14 @@ 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()];
> > + int cpu = ixgbe_determine_xdp_cpu(smp_processor_id());
> > + struct ixgbe_ring *ring = adapter->xdp_ring[cpu];
> >
> > - /* Force memory writes to complete before letting h/w
> > - * know there are new descriptors to fetch.
> > - */
> > - wmb();
> > - writel(ring->next_to_use, ring->tail);
> > + 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);
> > }
> >
> > u64_stats_update_begin(&rx_ring->syncp);
> > @@ -8539,21 +8543,33 @@ static u16 ixgbe_select_queue(struct net_device *dev, struct sk_buff *skb,
> > int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,
> > struct xdp_frame *xdpf)
> > {
> > - struct ixgbe_ring *ring = adapter->xdp_ring[smp_processor_id()];
> > + struct ixgbe_ring *ring;
>
> RCT is being broken in here
Sorry, I have no idea about what the RCT is. Is that kind of format?
Does that mean I should change the position of those lines to make it
look better?
>
> > struct ixgbe_tx_buffer *tx_buffer;
> > union ixgbe_adv_tx_desc *tx_desc;
> > u32 len, cmd_type;
> > dma_addr_t dma;
> > u16 i;
> > + int cpu;
> > + int ret;
>
> Ditto
>
> >
> > len = xdpf->len;
> >
> > - if (unlikely(!ixgbe_desc_unused(ring)))
> > - return IXGBE_XDP_CONSUMED;
> > + cpu = ixgbe_determine_xdp_cpu(smp_processor_id());
> > + ring = adapter->xdp_ring[cpu];
> > +
> > + if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> > + spin_lock(&ring->tx_lock);
> > +
> > + if (unlikely(!ixgbe_desc_unused(ring))) {
> > + ret = IXGBE_XDP_CONSUMED;
> > + goto out;
> > + }
> >
> > dma = dma_map_single(ring->dev, xdpf->data, len, DMA_TO_DEVICE);
> > - if (dma_mapping_error(ring->dev, dma))
> > - return IXGBE_XDP_CONSUMED;
> > + if (dma_mapping_error(ring->dev, dma)) {
> > + ret = IXGBE_XDP_CONSUMED;
> > + goto out;
> > + }
> >
> > /* record the location of the first descriptor for this packet */
> > tx_buffer = &ring->tx_buffer_info[ring->next_to_use];
> > @@ -8590,7 +8606,11 @@ int ixgbe_xmit_xdp_ring(struct ixgbe_adapter *adapter,
> > tx_buffer->next_to_watch = tx_desc;
> > ring->next_to_use = i;
> >
> > - return IXGBE_XDP_TX;
> > + ret = IXGBE_XDP_TX;
> > +out:
> > + if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> > + spin_unlock(&ring->tx_lock);
> > + return ret;
> > }
> >
> > netdev_tx_t ixgbe_xmit_frame_ring(struct sk_buff *skb,
> > @@ -10130,8 +10150,13 @@ 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 > MAX_XDP_QUEUES * 2)
>
> I realized this macro is a bit confusing, maybe it would be better to
> prefix it with the driver name, so IXGBE_MAX_XDP_QS would make it clear
> what's the scope of it.
>
You're right. It would be much clearer.
> > return -ENOMEM;
> > + else if (nr_cpu_ids > MAX_XDP_QUEUES)
> > + static_branch_inc(&ixgbe_xdp_locking_key);
> >
> > old_prog = xchg(&adapter->xdp_prog, prog);
> > need_reset = (!!prog != !!old_prog);
> > @@ -10201,6 +10226,7 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
> > struct ixgbe_adapter *adapter = netdev_priv(dev);
> > struct ixgbe_ring *ring;
> > int nxmit = 0;
> > + int cpu;
> > int i;
> >
> > if (unlikely(test_bit(__IXGBE_DOWN, &adapter->state)))
> > @@ -10209,10 +10235,12 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
> > if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
> > return -EINVAL;
> >
> > + cpu = ixgbe_determine_xdp_cpu(smp_processor_id());
>
> Actually it's not the cpu that you're determining, just a queue index in
> the xdp_rings array.
>
> Say that your running napi on cpu 72, so your function above will return
> you the 8 probably and that's the queue number you will pick and share
> with cpu 8.
>
> Can you rename this to ixgbe_determine_xdp_q_idx ?
>
Thanks. I'll do that.
> > +
> > /* 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 ? adapter->xdp_ring[cpu] : NULL;
> > if (unlikely(!ring))
> > return -ENXIO;
> >
> > @@ -10229,8 +10257,13 @@ static int ixgbe_xdp_xmit(struct net_device *dev, int n,
> > nxmit++;
> > }
> >
> > - if (unlikely(flags & XDP_XMIT_FLUSH))
> > + if (unlikely(flags & XDP_XMIT_FLUSH)) {
> > + 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);
> > + }
> >
> > return nxmit;
> > }
> > diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> > index b1d22e4..e9ce6c1 100644
> > --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> > +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> > @@ -334,13 +334,14 @@ 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()];
> > -
> > - /* Force memory writes to complete before letting h/w
> > - * know there are new descriptors to fetch.
> > - */
> > - wmb();
> > - writel(ring->next_to_use, ring->tail);
> > + int cpu = ixgbe_determine_xdp_cpu(smp_processor_id());
> > + struct ixgbe_ring *ring = adapter->xdp_ring[cpu];
> > +
> > + if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> > + spin_lock(&ring->tx_lock);
> > + ixgbe_xdp_ring_update_tail(ring);
>
> Good that ixgbe_xdp_ring_update_tail is reused, but probably this could be
> a common inlined function that is called on both normal and zc variants of
> clean rx irq routine.
>
Fine. I'll wrap them all together into one inline function.
> > + if (static_branch_unlikely(&ixgbe_xdp_locking_key))
> > + spin_unlock(&ring->tx_lock);
> > }
> >
> > u64_stats_update_begin(&rx_ring->syncp);
> > --
> > 1.8.3.1
> >
