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Message-ID: <ZEGd5QHTInP8WRlZ@boxer>
Date: Thu, 20 Apr 2023 22:17:41 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Gerhard Engleder <gerhard@...leder-embedded.com>
CC: <netdev@...r.kernel.org>, <bpf@...r.kernel.org>,
<davem@...emloft.net>, <kuba@...nel.org>, <edumazet@...gle.com>,
<pabeni@...hat.com>, <bjorn@...nel.org>,
<magnus.karlsson@...el.com>, <jonathan.lemon@...il.com>
Subject: Re: [PATCH net-next v3 6/6] tsnep: Add XDP socket zero-copy TX
support
On Tue, Apr 18, 2023 at 09:04:59PM +0200, Gerhard Engleder wrote:
> Send and complete XSK pool frames within TX NAPI context. NAPI context
> is triggered by ndo_xsk_wakeup.
>
> Test results with A53 1.2GHz:
>
> xdpsock txonly copy mode:
> pps pkts 1.00
> tx 284,409 11,398,144
> Two CPUs with 100% and 10% utilization.
>
> xdpsock txonly zero-copy mode:
> pps pkts 1.00
> tx 511,929 5,890,368
> Two CPUs with 100% and 1% utilization.
Hmm, I think l2fwd ZC numbers should be included here not in the previous
patch?
>
> Packet rate increases and CPU utilization is reduced.
>
> Signed-off-by: Gerhard Engleder <gerhard@...leder-embedded.com>
> ---
> drivers/net/ethernet/engleder/tsnep.h | 2 +
> drivers/net/ethernet/engleder/tsnep_main.c | 127 +++++++++++++++++++--
> 2 files changed, 119 insertions(+), 10 deletions(-)
>
(...)
> +static int tsnep_xdp_tx_map_zc(struct xdp_desc *xdpd, struct tsnep_tx *tx)
> +{
> + struct tsnep_tx_entry *entry;
> + dma_addr_t dma;
> +
> + entry = &tx->entry[tx->write];
> + entry->zc = true;
> +
> + dma = xsk_buff_raw_get_dma(tx->xsk_pool, xdpd->addr);
> + xsk_buff_raw_dma_sync_for_device(tx->xsk_pool, dma, xdpd->len);
> +
> + entry->type = TSNEP_TX_TYPE_XSK;
> + entry->len = xdpd->len;
> +
> + entry->desc->tx = __cpu_to_le64(dma);
> +
> + return xdpd->len;
> +}
> +
> +static void tsnep_xdp_xmit_frame_ring_zc(struct xdp_desc *xdpd,
> + struct tsnep_tx *tx)
> +{
> + int length;
> +
> + length = tsnep_xdp_tx_map_zc(xdpd, tx);
> +
> + tsnep_tx_activate(tx, tx->write, length, true);
> + tx->write = (tx->write + 1) & TSNEP_RING_MASK;
> +}
> +
> +static void tsnep_xdp_xmit_zc(struct tsnep_tx *tx)
> +{
> + int desc_available = tsnep_tx_desc_available(tx);
> + struct xdp_desc *descs = tx->xsk_pool->tx_descs;
> + int batch, i;
> +
> + /* ensure that TX ring is not filled up by XDP, always MAX_SKB_FRAGS
> + * will be available for normal TX path and queue is stopped there if
> + * necessary
> + */
> + if (desc_available <= (MAX_SKB_FRAGS + 1))
> + return;
> + desc_available -= MAX_SKB_FRAGS + 1;
> +
> + batch = xsk_tx_peek_release_desc_batch(tx->xsk_pool, desc_available);
> + for (i = 0; i < batch; i++)
> + tsnep_xdp_xmit_frame_ring_zc(&descs[i], tx);
> +
> + if (batch) {
> + /* descriptor properties shall be valid before hardware is
> + * notified
> + */
> + dma_wmb();
> +
> + tsnep_xdp_xmit_flush(tx);
> + }
> +}
> +
> static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget)
> {
> struct tsnep_tx_entry *entry;
> struct netdev_queue *nq;
> + int xsk_frames = 0;
> int budget = 128;
> int length;
> int count;
> @@ -676,7 +771,7 @@ static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget)
> if ((entry->type & TSNEP_TX_TYPE_SKB) &&
> skb_shinfo(entry->skb)->nr_frags > 0)
> count += skb_shinfo(entry->skb)->nr_frags;
> - else if (!(entry->type & TSNEP_TX_TYPE_SKB) &&
> + else if ((entry->type & TSNEP_TX_TYPE_XDP) &&
> xdp_frame_has_frags(entry->xdpf))
> count += xdp_get_shared_info_from_frame(entry->xdpf)->nr_frags;
>
> @@ -705,9 +800,11 @@ static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget)
>
> if (entry->type & TSNEP_TX_TYPE_SKB)
> napi_consume_skb(entry->skb, napi_budget);
> - else
> + else if (entry->type & TSNEP_TX_TYPE_XDP)
> xdp_return_frame_rx_napi(entry->xdpf);
> - /* xdpf is union with skb */
> + else
> + xsk_frames++;
> + /* xdpf and zc are union with skb */
> entry->skb = NULL;
>
> tx->read = (tx->read + count) & TSNEP_RING_MASK;
> @@ -718,6 +815,14 @@ static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget)
> budget--;
> } while (likely(budget));
>
> + if (tx->xsk_pool) {
> + if (xsk_frames)
> + xsk_tx_completed(tx->xsk_pool, xsk_frames);
> + if (xsk_uses_need_wakeup(tx->xsk_pool))
> + xsk_set_tx_need_wakeup(tx->xsk_pool);
> + tsnep_xdp_xmit_zc(tx);
would be good to signal to NAPI if we are done with the work or is there a
need to be rescheduled (when you didn't manage to consume all of the descs
from XSK Tx ring).
> + }
> +
> if ((tsnep_tx_desc_available(tx) >= ((MAX_SKB_FRAGS + 1) * 2)) &&
> netif_tx_queue_stopped(nq)) {
> netif_tx_wake_queue(nq);
> @@ -765,12 +870,6 @@ static int tsnep_tx_open(struct tsnep_tx *tx)
>
> static void tsnep_tx_close(struct tsnep_tx *tx)
> {
> - u32 val;
> -
> - readx_poll_timeout(ioread32, tx->addr + TSNEP_CONTROL, val,
> - ((val & TSNEP_CONTROL_TX_ENABLE) == 0), 10000,
> - 1000000);
> -
> tsnep_tx_ring_cleanup(tx);
> }
>
> @@ -1786,12 +1885,18 @@ static void tsnep_queue_enable(struct tsnep_queue *queue)
> napi_enable(&queue->napi);
> tsnep_enable_irq(queue->adapter, queue->irq_mask);
>
> + if (queue->tx)
> + tsnep_tx_enable(queue->tx);
> +
> if (queue->rx)
> tsnep_rx_enable(queue->rx);
> }
>
> static void tsnep_queue_disable(struct tsnep_queue *queue)
> {
> + if (queue->tx)
> + tsnep_tx_disable(queue->tx, &queue->napi);
> +
> napi_disable(&queue->napi);
> tsnep_disable_irq(queue->adapter, queue->irq_mask);
>
> @@ -1908,6 +2013,7 @@ int tsnep_enable_xsk(struct tsnep_queue *queue, struct xsk_buff_pool *pool)
> if (running)
> tsnep_queue_disable(queue);
>
> + queue->tx->xsk_pool = pool;
> queue->rx->xsk_pool = pool;
>
> if (running) {
> @@ -1928,6 +2034,7 @@ void tsnep_disable_xsk(struct tsnep_queue *queue)
> tsnep_rx_free_zc(queue->rx);
>
> queue->rx->xsk_pool = NULL;
> + queue->tx->xsk_pool = NULL;
>
> if (running) {
> tsnep_rx_reopen(queue->rx);
> --
> 2.30.2
>
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