From: Russell King - ARM Linux <linux@arm.linux.org.uk> To: Arnd Bergmann <arnd@arndb.de> Cc: Zhangfei Gao <zhangfei.gao@linaro.org>, davem@davemloft.net, f.fainelli@gmail.com, sergei.shtylyov@cogentembedded.com, mark.rutland@arm.com, David.Laight@aculab.com, eric.dumazet@gmail.com, linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org, devicetree@vger.kernel.org Subject: Re: [PATCH 3/3] net: hisilicon: new hip04 ethernet driver Date: Thu, 3 Apr 2014 16:27:46 +0100 [thread overview] Message-ID: <20140403152746.GQ7528@n2100.arm.linux.org.uk> (raw) In-Reply-To: <9532591.5yuCbpL4pV@wuerfel> On Wed, Apr 02, 2014 at 11:21:45AM +0200, Arnd Bergmann wrote: > - As David Laight pointed out earlier, you must also ensure that > you don't have too much /data/ pending in the descriptor ring > when you stop the queue. For a 10mbit connection, you have already > tested (as we discussed on IRC) that 64 descriptors with 1500 byte > frames gives you a 68ms round-trip ping time, which is too much. > Conversely, on 1gbit, having only 64 descriptors actually seems > a little low, and you may be able to get better throughput if > you extend the ring to e.g. 512 descriptors. You don't manage that by stopping the queue - there's separate interfaces where you report how many bytes you've queued (netdev_sent_queue()) and how many bytes/packets you've sent (netdev_tx_completed_queue()). This allows the netdev schedulers to limit how much data is held in the queue, preserving interactivity while allowing the advantages of larger rings. > > + phys = dma_map_single(&ndev->dev, skb->data, skb->len, DMA_TO_DEVICE); > > + if (dma_mapping_error(&ndev->dev, phys)) { > > + dev_kfree_skb(skb); > > + return NETDEV_TX_OK; > > + } > > + > > + priv->tx_skb[tx_head] = skb; > > + priv->tx_phys[tx_head] = phys; > > + desc->send_addr = cpu_to_be32(phys); > > + desc->send_size = cpu_to_be16(skb->len); > > + desc->cfg = cpu_to_be32(DESC_DEF_CFG); > > + phys = priv->tx_desc_dma + tx_head * sizeof(struct tx_desc); > > + desc->wb_addr = cpu_to_be32(phys); > > One detail: since you don't have cache-coherent DMA, "desc" will > reside in uncached memory, so you try to minimize the number of accesses. > It's probably faster if you build the descriptor on the stack and > then atomically copy it over, rather than assigning each member at > a time. DMA coherent memory is write combining, so multiple writes will be coalesced. This also means that barriers may be required to ensure the descriptors are pushed out in a timely manner if something like writel() is not used in the transmit-triggering path. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it.
WARNING: multiple messages have this Message-ID (diff)
From: linux@arm.linux.org.uk (Russell King - ARM Linux) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH 3/3] net: hisilicon: new hip04 ethernet driver Date: Thu, 3 Apr 2014 16:27:46 +0100 [thread overview] Message-ID: <20140403152746.GQ7528@n2100.arm.linux.org.uk> (raw) In-Reply-To: <9532591.5yuCbpL4pV@wuerfel> On Wed, Apr 02, 2014 at 11:21:45AM +0200, Arnd Bergmann wrote: > - As David Laight pointed out earlier, you must also ensure that > you don't have too much /data/ pending in the descriptor ring > when you stop the queue. For a 10mbit connection, you have already > tested (as we discussed on IRC) that 64 descriptors with 1500 byte > frames gives you a 68ms round-trip ping time, which is too much. > Conversely, on 1gbit, having only 64 descriptors actually seems > a little low, and you may be able to get better throughput if > you extend the ring to e.g. 512 descriptors. You don't manage that by stopping the queue - there's separate interfaces where you report how many bytes you've queued (netdev_sent_queue()) and how many bytes/packets you've sent (netdev_tx_completed_queue()). This allows the netdev schedulers to limit how much data is held in the queue, preserving interactivity while allowing the advantages of larger rings. > > + phys = dma_map_single(&ndev->dev, skb->data, skb->len, DMA_TO_DEVICE); > > + if (dma_mapping_error(&ndev->dev, phys)) { > > + dev_kfree_skb(skb); > > + return NETDEV_TX_OK; > > + } > > + > > + priv->tx_skb[tx_head] = skb; > > + priv->tx_phys[tx_head] = phys; > > + desc->send_addr = cpu_to_be32(phys); > > + desc->send_size = cpu_to_be16(skb->len); > > + desc->cfg = cpu_to_be32(DESC_DEF_CFG); > > + phys = priv->tx_desc_dma + tx_head * sizeof(struct tx_desc); > > + desc->wb_addr = cpu_to_be32(phys); > > One detail: since you don't have cache-coherent DMA, "desc" will > reside in uncached memory, so you try to minimize the number of accesses. > It's probably faster if you build the descriptor on the stack and > then atomically copy it over, rather than assigning each member at > a time. DMA coherent memory is write combining, so multiple writes will be coalesced. This also means that barriers may be required to ensure the descriptors are pushed out in a timely manner if something like writel() is not used in the transmit-triggering path. -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it.
next prev parent reply other threads:[~2014-04-03 15:28 UTC|newest] Thread overview: 130+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-04-01 13:27 [PATCH v5 0/3] add hisilicon hip04 ethernet driver Zhangfei Gao 2014-04-01 13:27 ` Zhangfei Gao 2014-04-01 13:27 ` [PATCH 1/3] Documentation: add Device tree bindings for Hisilicon hip04 ethernet Zhangfei Gao 2014-04-01 13:27 ` Zhangfei Gao [not found] ` <1396358832-15828-1-git-send-email-zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> 2014-04-01 13:27 ` [PATCH 2/3] net: hisilicon: new hip04 MDIO driver Zhangfei Gao 2014-04-01 13:27 ` Zhangfei Gao 2014-04-04 15:42 ` Zhangfei Gao 2014-04-04 15:42 ` Zhangfei Gao 2014-04-04 17:48 ` David Miller 2014-04-04 17:48 ` David Miller 2014-04-01 13:27 ` [PATCH 3/3] net: hisilicon: new hip04 ethernet driver Zhangfei Gao 2014-04-01 13:27 ` Zhangfei Gao [not found] ` <1396358832-15828-4-git-send-email-zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> 2014-04-02 9:21 ` Arnd Bergmann 2014-04-02 9:21 ` Arnd Bergmann 2014-04-02 9:51 ` zhangfei 2014-04-02 9:51 ` zhangfei 2014-04-02 15:24 ` Arnd Bergmann 2014-04-02 15:24 ` Arnd Bergmann 2014-04-02 10:04 ` David Laight 2014-04-02 10:04 ` David Laight 2014-04-02 15:49 ` Arnd Bergmann 2014-04-02 15:49 ` Arnd Bergmann 2014-04-03 6:24 ` Zhangfei Gao 2014-04-03 6:24 ` Zhangfei Gao [not found] ` <CAMj5BkgfwE1hHpVeqH9WRitwCB30x3c4w0qw7sXT3PiOV-QcPQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2014-04-03 8:35 ` Arnd Bergmann 2014-04-03 8:35 ` Arnd Bergmann 2014-04-03 15:22 ` David Miller 2014-04-03 15:22 ` David Miller 2014-04-03 15:38 ` zhangfei 2014-04-03 15:38 ` zhangfei 2014-04-03 15:27 ` Russell King - ARM Linux [this message] 2014-04-03 15:27 ` Russell King - ARM Linux 2014-04-03 15:42 ` David Laight 2014-04-03 15:42 ` David Laight 2014-04-03 15:50 ` Russell King - ARM Linux 2014-04-03 15:50 ` Russell King - ARM Linux 2014-04-03 17:57 ` Arnd Bergmann 2014-04-03 17:57 ` Arnd Bergmann 2014-04-04 6:52 ` Zhangfei Gao 2014-04-04 6:52 ` Zhangfei Gao -- strict thread matches above, loose matches on Subject: below -- 2014-04-05 4:35 [PATCH v7 0/3] add hisilicon " Zhangfei Gao 2014-04-05 4:35 ` [PATCH 3/3] net: hisilicon: new " Zhangfei Gao 2014-04-05 4:35 ` Zhangfei Gao 2014-04-07 18:53 ` David Miller 2014-04-07 18:53 ` David Miller 2014-04-08 8:07 ` zhangfei 2014-04-08 8:07 ` zhangfei 2014-04-08 8:30 ` David Laight 2014-04-08 8:30 ` David Laight [not found] ` <063D6719AE5E284EB5DD2968C1650D6D0F6F1434-VkEWCZq2GCInGFn1LkZF6NBPR1lH4CV8@public.gmane.org> 2014-04-08 9:42 ` Arnd Bergmann 2014-04-08 9:42 ` Arnd Bergmann 2014-04-08 14:47 ` zhangfei 2014-04-08 14:47 ` zhangfei 2014-04-18 13:17 ` zhangfei 2014-04-18 13:17 ` zhangfei 2014-04-07 18:56 ` David Miller 2014-04-07 18:56 ` David Miller 2014-04-04 15:16 [PATCH v6 0/3] add hisilicon " Zhangfei Gao [not found] ` <1396624597-390-1-git-send-email-zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> 2014-04-04 15:16 ` [PATCH 3/3] net: hisilicon: new " Zhangfei Gao 2014-04-04 15:16 ` Zhangfei Gao 2014-03-28 15:35 [PATCH v4 0/3] add hisilicon " Zhangfei Gao 2014-03-28 15:36 ` [PATCH 3/3] net: hisilicon: new " Zhangfei Gao 2014-03-28 15:36 ` Zhangfei Gao 2014-03-24 14:14 [PATCH v3 0/3] add hisilicon " Zhangfei Gao 2014-03-24 14:14 ` [PATCH 3/3] net: hisilicon: new " Zhangfei Gao 2014-03-24 14:14 ` Zhangfei Gao [not found] ` <1395670496-17381-4-git-send-email-zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> 2014-03-24 15:18 ` Arnd Bergmann 2014-03-24 15:18 ` Arnd Bergmann 2014-03-25 4:06 ` Zhangfei Gao 2014-03-25 4:06 ` Zhangfei Gao 2014-03-25 8:12 ` Arnd Bergmann 2014-03-25 8:12 ` Arnd Bergmann 2014-03-25 17:00 ` Florian Fainelli 2014-03-25 17:00 ` Florian Fainelli 2014-03-25 17:05 ` Arnd Bergmann 2014-03-25 17:05 ` Arnd Bergmann 2014-03-25 17:16 ` Florian Fainelli 2014-03-25 17:16 ` Florian Fainelli 2014-03-25 17:57 ` Arnd Bergmann 2014-03-25 17:57 ` Arnd Bergmann 2014-03-26 9:55 ` David Laight 2014-03-26 9:55 ` David Laight 2014-03-25 17:17 ` David Laight 2014-03-25 17:17 ` David Laight 2014-03-25 17:21 ` Eric Dumazet 2014-03-25 17:21 ` Eric Dumazet 2014-03-25 17:54 ` Arnd Bergmann 2014-03-25 17:54 ` Arnd Bergmann 2014-03-27 12:53 ` zhangfei 2014-03-27 12:53 ` zhangfei 2014-03-24 16:32 ` Florian Fainelli 2014-03-24 16:32 ` Florian Fainelli 2014-03-24 17:23 ` Arnd Bergmann 2014-03-24 17:23 ` Arnd Bergmann 2014-03-24 17:35 ` Florian Fainelli 2014-03-24 17:35 ` Florian Fainelli 2014-03-27 6:27 ` Zhangfei Gao 2014-03-27 6:27 ` Zhangfei Gao 2014-03-21 15:09 [PATCH v2 0/3] add hisilicon " Zhangfei Gao 2014-03-21 15:09 ` [PATCH 3/3] net: hisilicon: new " Zhangfei Gao 2014-03-21 15:09 ` Zhangfei Gao 2014-03-21 15:27 ` Arnd Bergmann 2014-03-21 15:27 ` Arnd Bergmann 2014-03-22 1:18 ` zhangfei 2014-03-22 1:18 ` zhangfei 2014-03-22 8:08 ` Arnd Bergmann 2014-03-22 8:08 ` Arnd Bergmann 2014-03-18 8:40 [PATCH 0/3] add hisilicon " Zhangfei Gao [not found] ` <1395132017-15928-1-git-send-email-zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> 2014-03-18 8:40 ` [PATCH 3/3] net: hisilicon: new " Zhangfei Gao 2014-03-18 8:40 ` Zhangfei Gao [not found] ` <1395132017-15928-4-git-send-email-zhangfei.gao-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> 2014-03-18 10:46 ` Russell King - ARM Linux 2014-03-18 10:46 ` Russell King - ARM Linux 2014-03-20 9:51 ` Zhangfei Gao 2014-03-20 9:51 ` Zhangfei Gao 2014-03-24 14:17 ` Rob Herring 2014-03-24 14:17 ` Rob Herring 2014-03-26 14:22 ` Zhangfei Gao 2014-03-26 14:22 ` Zhangfei Gao 2014-03-18 11:25 ` Arnd Bergmann 2014-03-18 11:25 ` Arnd Bergmann 2014-03-20 14:00 ` Zhangfei Gao 2014-03-20 14:00 ` Zhangfei Gao 2014-03-20 14:31 ` Arnd Bergmann 2014-03-20 14:31 ` Arnd Bergmann [not found] ` <201403201531.20416.arnd-r2nGTMty4D4@public.gmane.org> 2014-03-21 5:19 ` Zhangfei Gao 2014-03-21 5:19 ` Zhangfei Gao 2014-03-21 7:37 ` Arnd Bergmann 2014-03-21 7:37 ` Arnd Bergmann 2014-03-21 7:56 ` Zhangfei Gao 2014-03-21 7:56 ` Zhangfei Gao 2014-03-24 8:17 ` Zhangfei Gao 2014-03-24 8:17 ` Zhangfei Gao 2014-03-24 10:02 ` Arnd Bergmann 2014-03-24 10:02 ` Arnd Bergmann 2014-03-24 13:23 ` Zhangfei Gao 2014-03-24 13:23 ` Zhangfei Gao
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