netdev - Re: [PATCH mlx5-next] RDMA/mlx5: Don't use cached IRQ affinity mask

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Date:   Tue, 17 Jul 2018 11:46:40 +0300
From:   Max Gurtovoy <maxg@...lanox.com>
To:     Steve Wise <swise@...ngridcomputing.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Leon Romanovsky <leon@...nel.org>
CC:     Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH mlx5-next] RDMA/mlx5: Don't use cached IRQ affinity mask



On 7/16/2018 8:08 PM, Steve Wise wrote:
> Hey Max:
> 
> 

Hey,

> On 7/16/2018 11:46 AM, Max Gurtovoy wrote:
>>
>>
>> On 7/16/2018 5:59 PM, Sagi Grimberg wrote:
>>>
>>>> Hi,
>>>> I've tested this patch and seems problematic at this moment.
>>>
>>> Problematic how? what are you seeing?
>>
>> Connection failures and same error Steve saw:
>>
>> [Mon Jul 16 16:19:11 2018] nvme nvme0: Connect command failed, error
>> wo/DNR bit: -16402
>> [Mon Jul 16 16:19:11 2018] nvme nvme0: failed to connect queue: 2 ret=-18
>>
>>
>>>
>>>> maybe this is because of the bug that Steve mentioned in the NVMe
>>>> mailing list. Sagi mentioned that we should fix it in the NVMe/RDMA
>>>> initiator and I'll run his suggestion as well.
>>>
>>> Is your device irq affinity linear?
>>
>> When it's linear and the balancer is stopped the patch works.
>>
>>>
>>>> BTW, when I run the blk_mq_map_queues it works for every irq affinity.
>>>
>>> But its probably not aligned to the device vector affinity.
>>
>> but I guess it's better in some cases.
>>
>> I've checked the situation before Leon's patch and set all the vetcors
>> to CPU 0. In this case (I think that this was the initial report by
>> Steve), we use the affinity_hint (Israel's and Saeed's patches were we
>> use dev->priv.irq_info[vector].mask) and it worked fine.
>>
>> Steve,
>> Can you share your configuration (kernel, HCA, affinity map, connect
>> command, lscpu) ?
>> I want to repro it in my lab.
>>
> 
> - linux-4.18-rc1 + the nvme/nvmet inline_data_size patches + patches to
> enable ib_get_vector_affinity() in cxgb4 + sagi's patch + leon's mlx5
> patch so I can change the affinity via procfs.

ohh, now I understand that you where complaining regarding the affinity 
change reflection to mlx5_ib_get_vector_affinity and not regarding the 
failures on connecting while the affinity overlaps (that is working good 
before Leon's patch).
So this is a known issue since we used a static hint that never changes
from dev->priv.irq_info[vector].mask.

IMO we must fulfil the user wish to connect to N queues and not reduce 
it because of affinity overlaps. So in order to push Leon's patch we 
must also fix the blk_mq_rdma_map_queues to do a best effort mapping 
according the affinity and map the rest in naive way (in that way we 
will *always* map all the queues).

-Max.