svn commit: r341586 - head/sys/dev/mlx5/mlx5_en
Slava Shwartsman
slavash at FreeBSD.org
Wed May 1 08:06:07 UTC 2019
On 01-May-19 10:28, Slava Shwartsman wrote:
>
>
> 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
Got it now:
panic: Assertion m->m_pkthdr.snd_tag == NULL failed at
/usr/src/sys/netinet/ip_output.c:213
cpuid = 0
time = 1556697834
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame
0xfffffe00005ac1f0
vpanic() at vpanic+0x19d/frame 0xfffffe00005ac240
panic() at panic+0x43/frame 0xfffffe00005ac2a0
ip_output() at ip_output+0x159f/frame 0xfffffe00005ac3f0
ip_forward() at ip_forward+0x38c/frame 0xfffffe00005ac4b0
ip_input() at ip_input+0x7f5/frame 0xfffffe00005ac560
netisr_dispatch_src() at netisr_dispatch_src+0xa2/frame 0xfffffe00005ac5d0
ether_demux() at ether_demux+0x147/frame 0xfffffe00005ac600
ether_nh_input() at ether_nh_input+0x403/frame 0xfffffe00005ac660
netisr_dispatch_src() at netisr_dispatch_src+0xa2/frame 0xfffffe00005ac6d0
ether_input() at ether_input+0x7d/frame 0xfffffe00005ac700
vlan_input() at vlan_input+0x1e7/frame 0xfffffe00005ac750
ether_demux() at ether_demux+0x12d/frame 0xfffffe00005ac780
ether_nh_input() at ether_nh_input+0x403/frame 0xfffffe00005ac7e0
netisr_dispatch_src() at netisr_dispatch_src+0xa2/frame 0xfffffe00005ac850
ether_input() at ether_input+0x7d/frame 0xfffffe00005ac880
mlx5e_rx_cq_comp() at mlx5e_rx_cq_comp+0x8b4/frame 0xfffffe00005ac9a0
mlx5_cq_completion() at mlx5_cq_completion+0x5e/frame 0xfffffe00005ac9d0
mlx5_msix_handler() at mlx5_msix_handler+0x1ba/frame 0xfffffe00005aca10
ithread_loop() at ithread_loop+0x187/frame 0xfffffe00005aca70
fork_exit() at fork_exit+0x84/frame 0xfffffe00005acab0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00005acab0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
KDB: enter: panic
[ thread pid 12 tid 100113 ]
Stopped at kdb_enter+0x3b: movq $0,kdb_why
I can keep the machine in this state for a while now if you want to take
a look at anything specific.
Slava
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