From: Jakub Kicinski <kuba@kernel.org>
To: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Rob Herring <robh+dt@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Matthias Brugger <matthias.bgg@gmail.com>,
John Crispin <john@phrozen.org>,
Sean Wang <sean.wang@mediatek.com>,
Mark Lee <Mark-MC.Lee@mediatek.com>,
Arnd Bergmann <arnd@arndb.de>,
Fabien Parent <fparent@baylibre.com>,
devicetree <devicetree@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-mediatek@lists.infradead.org,
Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: Re: [PATCH 06/11] net: ethernet: mtk-eth-mac: new driver
Date: Wed, 6 May 2020 10:19:53 -0700 [thread overview]
Message-ID: <20200506101953.208e5366@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <CAMRc=MfmuKd64YaqrkhGFThDZd0_tRecR5H0QLY0cDJWSM-VgQ@mail.gmail.com>
On Wed, 6 May 2020 09:09:52 +0200 Bartosz Golaszewski wrote:
> > > +}
> >
> > Why do you clean the TX ring from a work rather than from the NAPI
> > context?
>
> So this was unclear to me, that's why I went with a workqueue. The
> budget argument in napi poll is for RX. Should I put some cap on the
> number of TX descriptors processed in napi context?
The prevailing wisdom is to not count the TX cleanup as work at all.
I think the best practice is to first clean up all the TX you can,
and then do at must @budget of RX.
Perhaps one day we will come up with a good way of capping TX, but
today not counting it towards budget is the safe choice.
> > > +static int mtk_mac_receive_packet(struct mtk_mac_priv *priv)
> > > +{
> > > + struct net_device *ndev = mtk_mac_get_netdev(priv);
> > > + struct mtk_mac_ring *ring = &priv->rx_ring;
> > > + struct device *dev = mtk_mac_get_dev(priv);
> > > + struct mtk_mac_ring_desc_data desc_data;
> > > + struct sk_buff *new_skb;
> > > + int ret;
> > > +
> > > + mtk_mac_lock(priv);
> > > + ret = mtk_mac_ring_pop_tail(ring, &desc_data);
> > > + mtk_mac_unlock(priv);
> > > + if (ret)
> > > + return -1;
> > > +
> > > + mtk_mac_dma_unmap_rx(priv, &desc_data);
> > > +
> > > + if ((desc_data.flags & MTK_MAC_DESC_BIT_RX_CRCE) ||
> > > + (desc_data.flags & MTK_MAC_DESC_BIT_RX_OSIZE)) {
> > > + /* Error packet -> drop and reuse skb. */
> > > + new_skb = desc_data.skb;
> > > + goto map_skb;
> > > + }
> > > +
> > > + new_skb = mtk_mac_alloc_skb(ndev);
> > > + if (!new_skb) {
> > > + netdev_err(ndev, "out of memory for skb\n");
> >
> > No need for printing, kernel will complain loudly about oom.
> >
> > > + ndev->stats.rx_dropped++;
> > > + new_skb = desc_data.skb;
> > > + goto map_skb;
> > > + }
> > > +
> > > + skb_put(desc_data.skb, desc_data.len);
> > > + desc_data.skb->ip_summed = CHECKSUM_NONE;
> > > + desc_data.skb->protocol = eth_type_trans(desc_data.skb, ndev);
> > > + desc_data.skb->dev = ndev;
> > > + netif_receive_skb(desc_data.skb);
> > > +
> > > +map_skb:
> > > + desc_data.dma_addr = mtk_mac_dma_map_rx(priv, new_skb);
> > > + if (dma_mapping_error(dev, desc_data.dma_addr)) {
> > > + dev_kfree_skb(new_skb);
> > > + netdev_err(ndev, "DMA mapping error of RX descriptor\n");
> > > + return -ENOMEM;
> >
> > In this case nothing will ever replenish the RX ring right? If we hit
> > this condition 128 times the ring will be empty?
>
> Indeed. What should I do if this fails though?
I think if you move things around it should work:
skb = pop_tail();
if (!skb)
return;
new_skb = alloc();
if (!new_skb)
goto reuse;
dma_map(new_skb);
if (error)
goto reuse;
dma_unmap(skb);
if (do_packet_processing())
free(skb);
else
receive(skb);
put_on_ring(new_skb);
next prev parent reply other threads:[~2020-05-06 17:19 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 14:02 [PATCH 00/11] mediatek: add support for MediaTek Ethernet MAC Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 01/11] dt-bindings: add a binding document for MediaTek PERICFG controller Bartosz Golaszewski
2020-05-13 2:38 ` Rob Herring
2020-05-13 8:09 ` Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 02/11] dt-bindings: new: add yaml bindings for MediaTek Ethernet MAC Bartosz Golaszewski
2020-05-13 2:41 ` Rob Herring
2020-05-05 14:02 ` [PATCH 03/11] net: ethernet: mediatek: rename Kconfig prompt Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 04/11] net: ethernet: mediatek: remove unnecessary spaces from Makefile Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 05/11] net: core: provide devm_register_netdev() Bartosz Golaszewski
2020-05-05 17:31 ` Jakub Kicinski
2020-05-06 6:39 ` Bartosz Golaszewski
2020-05-06 17:12 ` Jakub Kicinski
2020-05-07 9:25 ` Bartosz Golaszewski
2020-05-07 16:53 ` Jakub Kicinski
2020-05-07 17:03 ` Bartosz Golaszewski
2020-05-07 22:56 ` Jakub Kicinski
2020-05-08 5:54 ` Heiner Kallweit
2020-05-08 18:39 ` Bartosz Golaszewski
2020-05-05 19:25 ` Edwin Peer
2020-05-06 6:46 ` Bartosz Golaszewski
2020-05-06 18:20 ` Edwin Peer
2020-05-05 14:02 ` [PATCH 06/11] net: ethernet: mtk-eth-mac: new driver Bartosz Golaszewski
2020-05-05 17:47 ` Andrew Lunn
2020-05-06 7:02 ` Bartosz Golaszewski
2020-05-05 18:04 ` Jakub Kicinski
2020-05-06 7:09 ` Bartosz Golaszewski
2020-05-06 17:19 ` Jakub Kicinski [this message]
2020-05-06 19:16 ` Leon Romanovsky
2020-05-06 19:23 ` Jakub Kicinski
2020-05-07 5:55 ` Leon Romanovsky
2020-05-07 22:50 ` Jakub Kicinski
2020-05-06 19:24 ` Joe Perches
[not found] ` <1588844771.5921.27.camel@mtksdccf07>
2020-05-07 10:50 ` Bartosz Golaszewski
2020-05-07 13:16 ` Andrew Lunn
2020-05-07 17:01 ` Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 07/11] ARM64: dts: mediatek: add pericfg syscon to mt8516.dtsi Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 08/11] ARM64: dts: mediatek: add the ethernet node " Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 09/11] ARM64: dts: mediatek: add an alias for ethernet0 for pumpkin boards Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 10/11] ARM64: dts: mediatek: add ethernet pins " Bartosz Golaszewski
2020-05-05 14:02 ` [PATCH 11/11] ARM64: dts: mediatek: enable ethernet on " Bartosz Golaszewski
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