[PATCH net-next v2 2/2] net: mvneta: Use cacheable memory to store the rx buffer DMA address
Gregory CLEMENT
gregory.clement at free-electrons.com
Fri Feb 17 05:30:03 PST 2017
Hi Jisheng,
On ven., févr. 17 2017, Jisheng Zhang <jszhang at marvell.com> wrote:
> In hot code path such as mvneta_rx_hwbm() and mvneta_rx_swbm, the
> buf_phys_addr field of rx_dec is accessed. The rx_desc is allocated by
> dma_alloc_coherent, it's uncacheable if the device isn't cache
> coherent, reading from uncached memory is fairly slow. This patch uses
> cacheable memory to store the rx buffer DMA address. We get the
> following performance data on Marvell BG4CT Platforms (tested with
> iperf):
>
> before the patch:
> recving 1GB in mvneta_rx_swbm() costs 1492659600 ns
>
> after the patch:
> recving 1GB in mvneta_rx_swbm() costs 1421565640 ns
>
> We saved 4.76% time.
I have just tested it and as I feared, with HWBM enabled, a simple iperf
just doesn't work.
Gregory
>
> Signed-off-by: Jisheng Zhang <jszhang at marvell.com>
> Suggested-by: Arnd Bergmann <arnd at arndb.de>
> ---
> drivers/net/ethernet/marvell/mvneta.c | 28 +++++++++++++++++-----------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 06df72b8da85..e24c3028fe1d 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -580,6 +580,9 @@ struct mvneta_rx_queue {
> /* Virtual address of the RX buffer */
> void **buf_virt_addr;
>
> + /* DMA address of the RX buffer */
> + dma_addr_t *buf_dma_addr;
> +
> /* Virtual address of the RX DMA descriptors array */
> struct mvneta_rx_desc *descs;
>
> @@ -1617,6 +1620,7 @@ static void mvneta_rx_desc_fill(struct mvneta_rx_desc *rx_desc,
>
> rx_desc->buf_phys_addr = phys_addr;
> i = rx_desc - rxq->descs;
> + rxq->buf_dma_addr[i] = phys_addr;
> rxq->buf_virt_addr[i] = virt_addr;
> }
>
> @@ -1900,22 +1904,22 @@ static void mvneta_rxq_drop_pkts(struct mvneta_port *pp,
> for (i = 0; i < rx_done; i++) {
> struct mvneta_rx_desc *rx_desc =
> mvneta_rxq_next_desc_get(rxq);
> + int index = rx_desc - rxq->descs;
> u8 pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_desc->status);
> struct mvneta_bm_pool *bm_pool;
>
> bm_pool = &pp->bm_priv->bm_pools[pool_id];
> /* Return dropped buffer to the pool */
> mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool,
> - rx_desc->buf_phys_addr);
> + rxq->buf_dma_addr[index]);
> }
> return;
> }
>
> for (i = 0; i < rxq->size; i++) {
> - struct mvneta_rx_desc *rx_desc = rxq->descs + i;
> void *data = rxq->buf_virt_addr[i];
>
> - dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr,
> + dma_unmap_single(pp->dev->dev.parent, rxq->buf_dma_addr[i],
> MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE);
> mvneta_frag_free(pp->frag_size, data);
> }
> @@ -1953,7 +1957,7 @@ static int mvneta_rx_swbm(struct mvneta_port *pp, int rx_todo,
> rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
> index = rx_desc - rxq->descs;
> data = rxq->buf_virt_addr[index];
> - phys_addr = rx_desc->buf_phys_addr;
> + phys_addr = rxq->buf_dma_addr[index];
>
> if (!mvneta_rxq_desc_is_first_last(rx_status) ||
> (rx_status & MVNETA_RXD_ERR_SUMMARY)) {
> @@ -2062,6 +2066,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
> /* Fairness NAPI loop */
> while (rx_done < rx_todo) {
> struct mvneta_rx_desc *rx_desc = mvneta_rxq_next_desc_get(rxq);
> + int index = rx_desc - rxq->descs;
> struct mvneta_bm_pool *bm_pool = NULL;
> struct sk_buff *skb;
> unsigned char *data;
> @@ -2074,7 +2079,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
> rx_status = rx_desc->status;
> rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE);
> data = (u8 *)(uintptr_t)rx_desc->buf_cookie;
> - phys_addr = rx_desc->buf_phys_addr;
> + phys_addr = rxq->buf_dma_addr[index];
> pool_id = MVNETA_RX_GET_BM_POOL_ID(rx_status);
> bm_pool = &pp->bm_priv->bm_pools[pool_id];
>
> @@ -2082,8 +2087,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
> (rx_status & MVNETA_RXD_ERR_SUMMARY)) {
> err_drop_frame_ret_pool:
> /* Return the buffer to the pool */
> - mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool,
> - rx_desc->buf_phys_addr);
> + mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool, phys_addr);
> err_drop_frame:
> dev->stats.rx_errors++;
> mvneta_rx_error(pp, rx_desc);
> @@ -2098,7 +2102,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
> goto err_drop_frame_ret_pool;
>
> dma_sync_single_range_for_cpu(dev->dev.parent,
> - rx_desc->buf_phys_addr,
> + phys_addr,
> MVNETA_MH_SIZE + NET_SKB_PAD,
> rx_bytes,
> DMA_FROM_DEVICE);
> @@ -2114,8 +2118,7 @@ static int mvneta_rx_hwbm(struct mvneta_port *pp, int rx_todo,
> rcvd_bytes += rx_bytes;
>
> /* Return the buffer to the pool */
> - mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool,
> - rx_desc->buf_phys_addr);
> + mvneta_bm_pool_put_bp(pp->bm_priv, bm_pool, phys_addr);
>
> /* leave the descriptor and buffer untouched */
> continue;
> @@ -4019,7 +4022,10 @@ static int mvneta_init(struct device *dev, struct mvneta_port *pp)
> rxq->buf_virt_addr = devm_kmalloc(pp->dev->dev.parent,
> rxq->size * sizeof(void *),
> GFP_KERNEL);
> - if (!rxq->buf_virt_addr)
> + rxq->buf_dma_addr = devm_kmalloc(pp->dev->dev.parent,
> + rxq->size * sizeof(dma_addr_t),
> + GFP_KERNEL);
> + if (!rxq->buf_virt_addr || !rxq->buf_dma_addr)
> return -ENOMEM;
> }
>
> --
> 2.11.0
>
>
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--
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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