Date: Tue, 03 Sep 2019 14:07:07 -0000 From: John Baldwin <jhb@FreeBSD.org> To: Hans Petter Selasky <hps@selasky.org>, "Andrey V. Elsukov" <bu7cher@yandex.ru>, Slava Shwartsman <slavash@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r341586 - head/sys/dev/mlx5/mlx5_en Message-ID: <7cea5305-4136-a0b6-487b-51307b1c6db9@FreeBSD.org> In-Reply-To: <bc601976-7d6b-f849-0305-66feb11a7130@selasky.org> References: <201812051425.wB5EP38T004562@repo.freebsd.org> <a1ff0879-abae-25c5-9350-809186d2cf85@yandex.ru> <bc601976-7d6b-f849-0305-66feb11a7130@selasky.org>
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On 4/16/19 8:32 AM, Hans Petter Selasky wrote: > On 4/16/19 4:39 PM, Andrey V. Elsukov wrote: >> On 05.12.2018 17:25, Slava Shwartsman wrote: >>> Author: slavash >>> Date: Wed Dec 5 14:25:03 2018 >>> New Revision: 341586 >>> URL: https://svnweb.freebsd.org/changeset/base/341586 >>> >>> Log: >>> mlx5en: Implement backpressure indication. >>> >>> The backpressure indication is implemented using an unlimited rate type of >>> mbuf send tag. When the upper layers typically the socket layer has obtained such >>> a tag, it can then query the destination driver queue for the current >>> amount of space available in the send queue. >>> >>> A single mbuf send tag may be referenced multiple times and a refcount has been added >>> to the mlx5e_priv structure to track its usage. Because the send tag resides >>> in the mlx5e_channel structure, there is no need to wait for refcounts to reach >>> zero until the mlx4en(4) driver is detached. The channels structure is persistant >>> during the lifetime of the mlx5en(4) driver it belongs to and can so be accessed >>> without any need of synchronization. >>> >>> The mlx5e_snd_tag structure was extended to contain a type field, because there are now >>> two different tag types which end up in the driver which need to be distinguished. >>> >>> Submitted by: hselasky@ >>> Approved by: hselasky (mentor) >>> MFC after: 1 week >>> Sponsored by: Mellanox Technologies >>> @@ -587,27 +609,33 @@ mlx5e_xmit(struct ifnet *ifp, struct mbuf *mb) >>> struct mlx5e_sq *sq; >>> int ret; >>> >>> - sq = mlx5e_select_queue(ifp, mb); >>> - if (unlikely(sq == NULL)) { >>> -#ifdef RATELIMIT >>> - /* Check for route change */ >>> - if (mb->m_pkthdr.snd_tag != NULL && >>> - mb->m_pkthdr.snd_tag->ifp != ifp) { >>> + if (mb->m_pkthdr.snd_tag != NULL) { >>> + sq = mlx5e_select_queue_by_send_tag(ifp, mb); >>> + if (unlikely(sq == NULL)) { >>> + /* Check for route change */ >>> + if (mb->m_pkthdr.snd_tag->ifp != ifp) { >>> + /* Free mbuf */ >>> + m_freem(mb); >>> + >>> + /* >>> + * Tell upper layers about route >>> + * change and to re-transmit this >>> + * packet: >>> + */ >>> + return (EAGAIN); >>> + } >> >> Hi, >> >> I just discovered something strange and found that this commit is the >> cause. >> The test system has mlx5en 100G interface. It has two vlans: vlan500 and >> vlan100. >> Via vlan500 it receives some packets flows. Then it routes these packets >> into vlan100. >> But packets are dropped in mlx5e_xmit() with EAGAIN error code. >> >> # dtrace -n 'fbt::ip6_output:return {printf("%d", arg1);}' >> dtrace: description 'fbt::ip6_output:return ' matched 1 probe >> CPU ID FUNCTION:NAME >> 23 54338 ip6_output:return 35 >> 16 54338 ip6_output:return 35 >> 21 54338 ip6_output:return 35 >> 22 54338 ip6_output:return 35 >> 24 54338 ip6_output:return 35 >> 23 54338 ip6_output:return 35 >> 14 54338 ip6_output:return 35 >> ^C >> >> # dtrace -n 'fbt::mlx5e_xmit:return {printf("%d", arg1);}' >> dtrace: description 'fbt::mlx5e_xmit:return ' matched 1 probe >> CPU ID FUNCTION:NAME >> 16 69030 mlx5e_xmit:return 35 >> 23 69030 mlx5e_xmit:return 35 >> 26 69030 mlx5e_xmit:return 35 >> 25 69030 mlx5e_xmit:return 35 >> 24 69030 mlx5e_xmit:return 35 >> 21 69030 mlx5e_xmit:return 35 >> 26 69030 mlx5e_xmit:return 35 >> ^C >> >> The kernel config is GENERIC. >> 13.0-CURRENT #9 r345758+82f3d57(svn_head)-dirty >> > > Hi, > > This might be a case where rcvif in the mbuf's pktheader is not cleared > before the packet is fed back on the wire. > > John Baldwin is working on the send tags implementation, to eliminate > the EAGAIN handling in the network drivers. I will try to push this branch sooner then since it affects more than just TLS. Part of the change includes a new flag we can use to assert that we aren't just getting a stale rcvif (though there are also now assertions in ip_output that should catch this case I think). -- John Baldwin
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