svn commit: r341586 - head/sys/dev/mlx5/mlx5_en
Slava Shwartsman
slavash at FreeBSD.org
Wed May 1 07:09:30 UTC 2019
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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