Date: Wed, 1 May 2019 10:09:19 +0300 From: Slava Shwartsman <slavash@FreeBSD.org> To: John Baldwin <jhb@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: <0e80cb1d-20b9-5b8c-330e-5f64a603ff10@FreeBSD.org> In-Reply-To: <67b638e0-8e6f-f960-b263-62eed8ce28b7@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> <67b638e0-8e6f-f960-b263-62eed8ce28b7@FreeBSD.org>
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On 30-Apr-19 00:14, John Baldwin wrote: > 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. > Hi John, I grabbed your branch (which doesn't build BTW due to libbe(3): Fix mis-application of patch (SHLIBDIR) so I just reverted it). The kernel doesn't panic in this scenario - it just that the packets are being dropped. So I added a kdb_backtrace right before the return (EAGAIN) in mlx5e_xmit: KDB: stack backtrace: db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0000547d90 mlx5e_xmit() at mlx5e_xmit+0x3d/frame 0xfffffe0000548160 vlan_transmit() at vlan_transmit+0xdc/frame 0xfffffe00005481d0 ether_output_frame() at ether_output_frame+0xa2/frame 0xfffffe0000548200 ether_output() at ether_output+0x689/frame 0xfffffe00005482a0 ip_output() at ip_output+0x13a4/frame 0xfffffe00005483f0 ip_forward() at ip_forward+0x344/frame 0xfffffe00005484b0 ip_input() at ip_input+0x7f5/frame 0xfffffe0000548560 netisr_dispatch_src() at netisr_dispatch_src+0xa2/frame 0xfffffe00005485d0 ether_demux() at ether_demux+0x147/frame 0xfffffe0000548600 ether_nh_input() at ether_nh_input+0x403/frame 0xfffffe0000548660 netisr_dispatch_src() at netisr_dispatch_src+0xa2/frame 0xfffffe00005486d0 ether_input() at ether_input+0x73/frame 0xfffffe0000548700 vlan_input() at vlan_input+0x1e7/frame 0xfffffe0000548750 ether_demux() at ether_demux+0x12d/frame 0xfffffe0000548780 ether_nh_input() at ether_nh_input+0x403/frame 0xfffffe00005487e0 netisr_dispatch_src() at netisr_dispatch_src+0xa2/frame 0xfffffe0000548850 ether_input() at ether_input+0x73/frame 0xfffffe0000548880 mlx5e_rx_cq_comp() at mlx5e_rx_cq_comp+0x8b4/frame 0xfffffe00005489a0 mlx5_cq_completion() at mlx5_cq_completion+0x5e/frame 0xfffffe00005489d0 mlx5_msix_handler() at mlx5_msix_handler+0x1ba/frame 0xfffffe0000548a10 ithread_loop() at ithread_loop+0x187/frame 0xfffffe0000548a70 fork_exit() at fork_exit+0x84/frame 0xfffffe0000548ab0 fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe0000548ab0 --- trap 0, rip = 0, rsp = 0, rbp = 0 --- Please ping me if you want me to try anything else. Slava
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