netdev - Re: [External] : Re: [PATCH 1/1] IB/mlx5: Add a signature check to received EQEs and CQEs

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Date:   Mon, 7 Nov 2022 09:51:36 -0800
From:   Rohit Nair <rohit.sajan.kumar@...cle.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     jgg@...pe.ca, saeedm@...dia.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, manjunath.b.patil@...cle.com,
        rama.nichanamatlu@...cle.com,
        Michael Guralnik <michaelgur@...dia.com>
Subject: Re: [External] : Re: [PATCH 1/1] IB/mlx5: Add a signature check to
 received EQEs and CQEs

On 11/6/22 10:03 AM, Leon Romanovsky wrote:
>>
>> rds-stress exercises the codepath we are modifying here. rds-stress didn't
>> show much of performance degrade when we ran internally. We also requested
>> our DB team for performance regression testing and this change passed their
>> test suite. This motivated us to submit this to upstream.
>>
>> If there is any other test that is better suited for this change, I am
>> willing to test it. Please let me know if you have something in mind. We can
>> revisit this patch after such a test may be.
>>
>> I agree that, this was a rare debug scenario, but it took lot more than
>> needed to narrow down[engaged vendor on live sessions]. We are adding this
>> in the hope to finding the cause at the earliest or at least point us which
>> direction to look at. We also requested the vendor[mlx] to include some
>> diagnostics[HW counter], which can help us narrow it faster next time. This
>> is our attempt to add kernel side of diagnostics.
> 
> The thing is that "vendor" failed to explain internally if this debug
> code is useful. Like I said, extremely rare debug code shouldn't be part
> of main data path.
> 
> Thanks
>

I understand.
Thank you for taking the time to review this patch.


Best,
Rohit.