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Date: Fri, 17 Feb 2017 14:30:03 +0100 From: Gregory CLEMENT <gregory.clement@...e-electrons.com> To: Jisheng Zhang <jszhang@...vell.com> Cc: <thomas.petazzoni@...e-electrons.com>, <davem@...emloft.net>, <arnd@...db.de>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH net-next v2 2/2] net: mvneta: Use cacheable memory to store the rx buffer DMA address Hi Jisheng, On ven., févr. 17 2017, Jisheng Zhang <jszhang@...vell.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@...vell.com> > Suggested-by: Arnd Bergmann <arnd@...db.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 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@...ts.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com
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