Date: Mon, 29 Apr 2019 14:14:19 -0700 From: John Baldwin <jhb@FreeBSD.org> To: slavash@FreeBSD.org, Hans Petter Selasky <hps@selasky.org>, "Andrey V. Elsukov" <bu7cher@yandex.ru>, 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: <67b638e0-8e6f-f960-b263-62eed8ce28b7@FreeBSD.org> In-Reply-To: <123654bf-59f7-1db8-55ce-36306bdac43d@FreeBSD.org> References: <201812051425.wB5EP38T004562@repo.freebsd.org> <a1ff0879-abae-25c5-9350-809186d2cf85@yandex.ru> <bc601976-7d6b-f849-0305-66feb11a7130@selasky.org> <7cea5305-4136-a0b6-487b-51307b1c6db9@FreeBSD.org> <123654bf-59f7-1db8-55ce-36306bdac43d@FreeBSD.org>
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On 4/25/19 12:10 AM, Slava Shwartsman wrote: > > > On 17-Apr-19 00:28, John Baldwin wrote: >> 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 > Thanks John! >> aren't just getting a stale rcvif (though there are also now assertions in >> ip_output that should catch this case I think). >> > > > > Hi Andrey, > > Yes, we were able to reproduce this issue in house. If you don't mind, I > prefer to wait for John's update - where he eliminates the EAGAIN > handling in the network drivers. I have rebased the branch for this, but for now it will just panic sooner I believe by tripping an assertion. Can you grab the diff (or just the branch) from the 'send_tags' branch at github/bsdjhb/freebsd and reproduce under a kernel with INVARIANTS? I think we will have to explicitly clear the 'rcvif' pointer somewhere, but I want to see what the stack trace looks like so I can think about the "right" place to clear it. -- John Baldwin
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