Date: Wed, 1 May 2019 10:28:05 +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: <737bfa62-eb3e-7c48-6356-0e0b76bb0593@FreeBSD.org> In-Reply-To: <0e80cb1d-20b9-5b8c-330e-5f64a603ff10@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> <0e80cb1d-20b9-5b8c-330e-5f64a603ff10@FreeBSD.org>
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On 01-May-19 10:09, Slava Shwartsman wrote: > > > 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 My bad - tested with master. Re-testing now. Slava
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