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Tue, 08 Dec 2020 19:33:25 -0800 (PST) Date: Wed, 9 Dec 2020 11:33:14 +0800 From: Sieng Piaw Liew To: Eric Dumazet Cc: Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, netdev@vger.kernel.org, liew.s.piaw@gmail.com Subject: Re: [PATCH net-next] bcm63xx_enet: batch process rx path Message-ID: <20201209033314.GA38@DESKTOP-8REGVGF.localdomain> References: <20201204054616.26876-1-liew.s.piaw@gmail.com> <3caedd41-669e-94be-9214-e93eed5ae073@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3caedd41-669e-94be-9214-e93eed5ae073@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Dec 04, 2020 at 10:50:45AM +0100, Eric Dumazet wrote: > > > On 12/4/20 6:46 AM, Sieng Piaw Liew wrote: > > Use netif_receive_skb_list to batch process rx skb. > > Tested on BCM6328 320 MHz using iperf3 -M 512, increasing performance > > by 12.5%. > > > > > > Well, the real question is why you do not simply use GRO, > to get 100% performance gain or more for TCP flows. > > > netif_receive_skb_list() is no longer needed, > GRO layer already uses batching for non TCP packets. > > We probably should mark is deprecated. > > diff --git a/drivers/net/ethernet/broadcom/bcm63xx_enet.c b/drivers/net/ethernet/broadcom/bcm63xx_enet.c > index 916824cca3fda194c42fefec7f514ced1a060043..6fdbe231b7c1b27f523889bda8a20ab7eaab65a6 100644 > --- a/drivers/net/ethernet/broadcom/bcm63xx_enet.c > +++ b/drivers/net/ethernet/broadcom/bcm63xx_enet.c > @@ -391,7 +391,7 @@ static int bcm_enet_receive_queue(struct net_device *dev, int budget) > skb->protocol = eth_type_trans(skb, dev); > dev->stats.rx_packets++; > dev->stats.rx_bytes += len; > - netif_receive_skb(skb); > + napi_gro_receive_skb(&priv->napi, skb); > > } while (--budget > 0); > The bcm63xx router SoC does not have enough CPU power nor hardware accelerator to process checksum validation fast enough for GRO/GSO. I have tested napi_gro_receive() on LAN-WAN setup. The resulting bandwidth dropped from 95Mbps wire speed down to 80Mbps. And it's inconsistent, with spikes and drops of >5Mbps. The ag71xx driver for ath79 router SoC reverted its use for the same reason. http://lists.infradead.org/pipermail/lede-commits/2017-October/004864.html