Date: Thu, 25 Apr 2019 10:10:09 +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: <123654bf-59f7-1db8-55ce-36306bdac43d@FreeBSD.org> In-Reply-To: <7cea5305-4136-a0b6-487b-51307b1c6db9@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>
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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. Slava
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