Messages in this thread Patch in this message | | | From | Jesper Dangaard Brouer <> | Date | Thu, 3 Aug 2023 09:36:14 +0200 | Subject | Re: [PATCH V3 net-next] net: fec: add XDP_TX feature support |
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On 03/08/2023 05.58, Wei Fang wrote: >>> } else { >>> - xdp_return_frame(xdpf); >>> + xdp_return_frame_rx_napi(xdpf); >> >> If you implement Jesper's syncing suggestions, I think you can use >> >> page_pool_put_page(pool, page, 0, true);
To Jakub, using 0 here you are trying to bypass the DMA-sync (which is valid as driver knows XDP_TX have already done the sync). The code will still call into DMA-sync calls with zero as size, so wonder if we should detect size zero and skip that call? (I mean is this something page_pool should support.)
diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 7ca456bfab71..778d061e4f2c 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -323,7 +323,8 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool, dma_addr_t dma_addr = page_pool_get_dma_addr(page);
dma_sync_size = min(dma_sync_size, pool->p.max_len); - dma_sync_single_range_for_device(pool->p.dev, dma_addr, + if (dma_sync_size) + dma_sync_single_range_for_device(pool->p.dev, dma_addr, pool->p.offset, dma_sync_size, pool->p.dma_dir);
>> >> for XDP_TX here to avoid the DMA sync on page recycle. > > I tried Jasper's syncing suggestion and used page_pool_put_page() to recycle > pages, but the results does not seem to improve the performance of XDP_TX,
The optimization will only have effect on those devices which have dev->dma_coherent=false else DMA function [1] (e.g. dma_direct_sync_single_for_device) will skip the sync calls.
[1] https://elixir.bootlin.com/linux/v6.5-rc4/source/kernel/dma/direct.h#L63
(Cc. Andrew Lunn) Does any of the imx generations have dma-noncoherent memory?
And does any of these use the fec NIC driver?
> it even degrades the speed.
Could be low runs simply be a variation between your test runs?
The specific device (imx8mpevk) this was tested on, clearly have dma_coherent=true, or else we would have seen a difference. But the code change should not have any overhead for the dma_coherent=true case, the only extra overhead is the extra empty DMA sync call with size zero (as discussed in top).
> > The result of the current modification. > root@imx8mpevk:~# ./xdp2 eth0 > proto 17: 260180 pkt/s
These results are *significantly* better than reported in patch-1. What happened?!?
e.g. root@imx8mpevk:~# ./xdp2 eth0 proto 17: 135817 pkt/s proto 17: 142776 pkt/s
> proto 17: 260373 pkt/s > proto 17: 260363 pkt/s > proto 17: 259036 pkt/s > proto 17: 260180 pkt/s > proto 17: 260048 pkt/s > proto 17: 260029 pkt/s > proto 17: 260133 pkt/s > proto 17: 260021 pkt/s > proto 17: 260203 pkt/s > proto 17: 260293 pkt/s > proto 17: 259418 pkt/s > > After using the sync suggestion, the result shows as follow. > root@imx8mpevk:~# ./xdp2 eth0 > proto 17: 255956 pkt/s > proto 17: 255841 pkt/s > proto 17: 255835 pkt/s > proto 17: 255381 pkt/s > proto 17: 255736 pkt/s > proto 17: 255779 pkt/s > proto 17: 254135 pkt/s > proto 17: 255584 pkt/s > proto 17: 255855 pkt/s > proto 17: 255664 pkt/s > > Below are my changes, I don't know what cause it. Based on the results, > it's better to keep the current modification. > > diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c > index d5fda24a4c52..415c0cb83f84 100644 > --- a/drivers/net/ethernet/freescale/fec_main.c > +++ b/drivers/net/ethernet/freescale/fec_main.c > @@ -77,7 +77,8 @@ > static void set_multicast_list(struct net_device *ndev); > static void fec_enet_itr_coal_set(struct net_device *ndev); > static int fec_enet_xdp_tx_xmit(struct net_device *ndev, > - struct xdp_buff *xdp); > + struct xdp_buff *xdp, > + u32 dma_sync_len); > > #define DRIVER_NAME "fec" > > @@ -1487,7 +1488,14 @@ fec_enet_tx_queue(struct net_device *ndev, u16 queue_id, int budget) > /* Free the sk buffer associated with this last transmit */ > dev_kfree_skb_any(skb); > } else { > - xdp_return_frame_rx_napi(xdpf); > + if (txq->tx_buf[index].type == FEC_TXBUF_T_XDP_NDO) > + xdp_return_frame_rx_napi(xdpf); > + else { > + struct page *page; > + > + page = virt_to_head_page(xdpf->data); > + page_pool_put_page(page->pp, page, 0, true); > + } > > txq->tx_buf[index].xdp = NULL; > /* restore default tx buffer type: FEC_TXBUF_T_SKB */ > @@ -1557,7 +1565,8 @@ fec_enet_run_xdp(struct fec_enet_private *fep, struct bpf_prog *prog, > act = bpf_prog_run_xdp(prog, xdp); > > /* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */ > - sync = xdp->data_end - xdp->data_hard_start - FEC_ENET_XDP_HEADROOM; > + sync = xdp->data_end - xdp->data; > sync = max(sync, len); > > switch (act) { > @@ -1579,7 +1588,7 @@ fec_enet_run_xdp(struct fec_enet_private *fep, struct bpf_prog *prog, > break; > > case XDP_TX: > - err = fec_enet_xdp_tx_xmit(fep->netdev, xdp); > + err = fec_enet_xdp_tx_xmit(fep->netdev, xdp, sync); > if (unlikely(err)) { > ret = FEC_ENET_XDP_CONSUMED; > page = virt_to_head_page(xdp->data); > @@ -3807,6 +3816,7 @@ fec_enet_xdp_get_tx_queue(struct fec_enet_private *fep, int index) > static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep, > struct fec_enet_priv_tx_q *txq, > struct xdp_frame *frame, > + u32 dma_sync_len, > bool ndo_xmit) > { > unsigned int index, status, estatus; > @@ -3840,7 +3850,7 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep, > dma_addr = page_pool_get_dma_addr(page) + sizeof(*frame) + > frame->headroom; > dma_sync_single_for_device(&fep->pdev->dev, dma_addr, > - frame->len, DMA_BIDIRECTIONAL); > + dma_sync_len, DMA_BIDIRECTIONAL); > txq->tx_buf[index].type = FEC_TXBUF_T_XDP_TX; > } > > @@ -3889,7 +3899,8 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep, > } > > static int fec_enet_xdp_tx_xmit(struct net_device *ndev, > - struct xdp_buff *xdp) > + struct xdp_buff *xdp, > + u32 dma_sync_len) > { > struct xdp_frame *xdpf = xdp_convert_buff_to_frame(xdp); > struct fec_enet_private *fep = netdev_priv(ndev); > @@ -3909,7 +3920,7 @@ static int fec_enet_xdp_tx_xmit(struct net_device *ndev, > > /* Avoid tx timeout as XDP shares the queue with kernel stack */ > txq_trans_cond_update(nq); > - ret = fec_enet_txq_xmit_frame(fep, txq, xdpf, false); > + ret = fec_enet_txq_xmit_frame(fep, txq, xdpf, dma_sync_len, false); > > __netif_tx_unlock(nq); > > @@ -3938,7 +3949,7 @@ static int fec_enet_xdp_xmit(struct net_device *dev, > /* Avoid tx timeout as XDP shares the queue with kernel stack */ > txq_trans_cond_update(nq); > for (i = 0; i < num_frames; i++) { > - if (fec_enet_txq_xmit_frame(fep, txq, frames[i], true) < 0) > + if (fec_enet_txq_xmit_frame(fep, txq, frames[i], 0, true) < 0) > break; > sent_frames++; > } >
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