Re: [bug report] NVMe/IB: reset_controller need more than 1min

[Max Gurtovoy <mgurtovoy@nvidia.com>]

Hi Yi Zhang,

thanks for testing the patches.

Can you provide more info on the time it took with both kernels ?

The patches don't intend to decrease this time but re-start the KA in 
early stage - as soon as we create the AQ.

I guess we need to debug it offline.

On 2/21/2022 12:00 PM, Yi Zhang wrote:
> Hi Max
>
> The patch fixed the timeout issue when I use one non-debug kernel,
> but when I tested on debug kernel with your patches, the timeout still
> can be triggered with "nvme reset/nvme disconnect-all" operations.
>
> On Tue, Feb 15, 2022 at 10:31 PM Max Gurtovoy <mgurtovoy@nvidia.com> wrote:
>> Thanks Yi Zhang.
>>
>> Few years ago I've sent some patches that were supposed to fix the KA
>> mechanism but eventually they weren't accepted.
>>
>> I haven't tested it since but maybe you can run some tests with it.
>>
>> The attached patches are partial and include only rdma transport for
>> your testing.
>>
>> If it work for you we can work on it again and argue for correctness.
>>
>> Please don't use the workaround we suggested earlier with these patches.
>>
>> -Max.
>>
>> On 2/15/2022 3:52 PM, Yi Zhang wrote:
>>> Hi Sagi/Max
>>>
>>> Changing the value to 10 or 15 fixed the timeout issue.
>>> And the reset operation still needs more than 12s on my environment, I
>>> also tried disabling the pi_enable, the reset operation will be back
>>> to 3s, so seems the added 9s was due to the PI enabled code path.
>>>
>>> On Mon, Feb 14, 2022 at 8:12 PM Max Gurtovoy <mgurtovoy@nvidia.com> wrote:
>>>> On 2/14/2022 1:32 PM, Sagi Grimberg wrote:
>>>>>> Hi Sagi/Max
>>>>>> Here are more findings with the bisect:
>>>>>>
>>>>>> The time for reset operation changed from 3s[1] to 12s[2] after
>>>>>> commit[3], and after commit[4], the reset operation timeout at the
>>>>>> second reset[5], let me know if you need any testing for it, thanks.
>>>>> Does this at least eliminate the timeout?
>>>>> --
>>>>> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
>>>>> index a162f6c6da6e..60e415078893 100644
>>>>> --- a/drivers/nvme/host/nvme.h
>>>>> +++ b/drivers/nvme/host/nvme.h
>>>>> @@ -25,7 +25,7 @@ extern unsigned int nvme_io_timeout;
>>>>>    extern unsigned int admin_timeout;
>>>>>    #define NVME_ADMIN_TIMEOUT     (admin_timeout * HZ)
>>>>>
>>>>> -#define NVME_DEFAULT_KATO      5
>>>>> +#define NVME_DEFAULT_KATO      10
>>>>>
>>>>>    #ifdef CONFIG_ARCH_NO_SG_CHAIN
>>>>>    #define  NVME_INLINE_SG_CNT  0
>>>>> --
>>>>>
>>>> or for the initial test you can use --keep-alive-tmo=<10 or 15> flag in
>>>> the connect command
>>>>
>>>>>> [1]
>>>>>> # time nvme reset /dev/nvme0
>>>>>>
>>>>>> real 0m3.049s
>>>>>> user 0m0.000s
>>>>>> sys 0m0.006s
>>>>>> [2]
>>>>>> # time nvme reset /dev/nvme0
>>>>>>
>>>>>> real 0m12.498s
>>>>>> user 0m0.000s
>>>>>> sys 0m0.006s
>>>>>> [3]
>>>>>> commit 5ec5d3bddc6b912b7de9e3eb6c1f2397faeca2bc (HEAD)
>>>>>> Author: Max Gurtovoy <maxg@mellanox.com>
>>>>>> Date:   Tue May 19 17:05:56 2020 +0300
>>>>>>
>>>>>>        nvme-rdma: add metadata/T10-PI support
>>>>>>
>>>>>> [4]
>>>>>> commit a70b81bd4d9d2d6c05cfe6ef2a10bccc2e04357a (HEAD)
>>>>>> Author: Hannes Reinecke <hare@suse.de>
>>>>>> Date:   Fri Apr 16 13:46:20 2021 +0200
>>>>>>
>>>>>>        nvme: sanitize KATO setting-
>>>>> This change effectively changed the keep-alive timeout
>>>>> from 15 to 5 and modified the host to send keepalives every
>>>>> 2.5 seconds instead of 5.
>>>>>
>>>>> I guess that in combination that now it takes longer to
>>>>> create and delete rdma resources (either qps or mrs)
>>>>> it starts to timeout in setups where there are a lot of
>>>>> queues.
>
>