Dear Eric,
Sorry for the late reply. On 5/29/19 6:00 PM, Eric Dumazet wrote: > On Wed, May 29, 2019 at 7:49 AM Paul Menzel <[email protected]> wrote: >> On 05/28/19 19:18, Eric Dumazet wrote: >>> On 5/28/19 8:42 AM, Paul Menzel wrote: >> >>>> Occasionally, Linux outputs the message below on the workstation Dell >>>> OptiPlex 5040 MT. >>>> >>>> TCP: net00: Driver has suspect GRO implementation, TCP performance may >>>> be compromised. >>>> >>>> Linux 4.14.55 and Linux 5.2-rc2 show the message, and the WWW also >>>> gives some hits [1][2]. >>>> >>>> ``` >>>> $ sudo ethtool -i net00 >>>> driver: e1000e >>>> version: 3.2.6-k >>>> firmware-version: 0.8-4 >>>> expansion-rom-version: >>>> bus-info: 0000:00:1f.6 >>>> supports-statistics: yes >>>> supports-test: yes >>>> supports-eeprom-access: yes >>>> supports-register-dump: yes >>>> supports-priv-flags: no >>>> ``` >>>> >>>> Can the driver e1000e be improved? >>>> >>>> Any idea, what triggers this, as I do not see it every boot? Download >>>> of big files? >>>> >>> Maybe the driver/NIC can receive frames bigger than MTU, although this >>> would be strange. >>> >>> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c >>> index >>> c61edd023b352123e2a77465782e0d32689e96b0..cb0194f66125bcba427e6e7e3cacf0c93040ef61 >>> 100644 >>> --- a/net/ipv4/tcp_input.c >>> +++ b/net/ipv4/tcp_input.c >>> @@ -150,8 +150,10 @@ static void tcp_gro_dev_warn(struct sock *sk, const >>> struct sk_buff *skb, >>> rcu_read_lock(); >>> dev = dev_get_by_index_rcu(sock_net(sk), skb->skb_iif); >>> if (!dev || len >= dev->mtu) >>> - pr_warn("%s: Driver has suspect GRO implementation, >>> TCP performance may be compromised.\n", >>> - dev ? dev->name : "Unknown driver"); >>> + pr_warn("%s: Driver has suspect GRO implementation, >>> TCP performance may be compromised." >>> + " len %u mtu %u\n", >>> + dev ? dev->name : "Unknown driver", >>> + len, dev ? dev->mtu : 0); >>> rcu_read_unlock(); >>> } >>> } >> >> I applied your patch on commit 9fb67d643 (Merge tag 'pinctrl-v5.2-2' of >> git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl): >> >> [ 5507.291769] TCP: net00: Driver has suspect GRO implementation, TCP >> performance may be compromised. len 1856 mtu 1500 > > > The 'GRO' in the warning can be probably ignored, since this NIC does > not implement its own GRO. > > You can confirm this with this debug patch: > > diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c > b/drivers/net/ethernet/intel/e1000e/netdev.c > index > 0e09bede42a2bd2c912366a68863a52a22def8ee..014a43ce77e09664bda0568dd118064b006acd67 > 100644 > --- a/drivers/net/ethernet/intel/e1000e/netdev.c > +++ b/drivers/net/ethernet/intel/e1000e/netdev.c > @@ -561,6 +561,9 @@ static void e1000_receive_skb(struct e1000_adapter > *adapter, > if (staterr & E1000_RXD_STAT_VP) > __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), tag); > > + if (skb->len > netdev->mtu) > + pr_err_ratelimited("received packet bigger (%u) than > MTU (%u)\n", > + skb->len, netdev->mtu); > napi_gro_receive(&adapter->napi, skb); > } With this patch applied, I unfortunately could not trigger the condition anymore. No idea why. Or is that expected? (As a side note, plain Linux 5.2.2 still shows the warning.) Kind regards, Paul
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