Re: [PATCH V7 00/10] mmc: Add Command Queue support

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On 6 September 2017 at 09:20, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> On 05/09/17 20:54, Ulf Hansson wrote:
>> On 5 September 2017 at 10:10, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
>>> On 05/09/17 10:24, Ulf Hansson wrote:
>>>> [...]
>>>>
>>>>>>>
>>>>>>> I can send blk-mq support for legacy requests in a few days if you like, but
>>>>>>> I want to hear a better explanation of why you are delaying CQE support.
>>>>>>
>>>>>> That would be very nice, however be aware of that we are in the merge
>>>>>> window, so I am not picking new material for 4.14 from this point. I
>>>>>> assume you understand why.
>>>>>
>>>>> Nope.  This is new functionality - doesn't affect anyone who doesn't have a
>>>>> command queue engine.  Next to no chance of regressions.  Tested by several
>>>>> in the community.  Substantially unchanged since February.  It is not even
>>>>> very much code in the block driver.
>>>>
>>>> Let me make it clear, once more - I don't want to maintain more hacks
>>>> in mmc block layer code.
>>>>
>>>> This series add blkmq support, using a method (which may be considered
>>>> as intermediate) via a new change in patch1 - but only for the new CQE
>>>> path. That means the old legacy mmc block path is still there. So, for
>>>> the reason stated above - no thanks!
>>>
>>> And where is your alternative.  When I pointed out you need a way to
>>> arbitrate between internal partitions, you went silent again.
>>>
>>> Can't have CQE without blk-mq but can't have blk-mq because you don't
>>> understand it, is hardly acceptable.
>>
>> Adrian, this discussion seems to lead nowhere. Can we please stop and
>> be constructive instead!
>
> If you want to be constructive you will queue CQE support for v4.15 now!
>
>>
>> Regarding the arbitration issue. We have been moving forward,
>> re-factoring the mmc block driver code, soon also solving the problem
>> for the rpmb internal partition [1]. Maybe the background to why Linus
>> is working on mmc block re-factoring, hasn't been entirely clear.
>> Anyway, it's exactly because of moving closer to address these issues.
>
> Nope, wrt blk-mq you are moving sideways with no clear idea where you're going.
>
>> Even if the problems certainly becomes a step harder to resolve for
>> the boot and the general purpose partitions, it's still a path we
>> should try to find a solution for. Yeah, that may mean we need to
>> suggest changes for the generic block layer, to teach it to better
>> deal with these kind of devices.
>
> You mean you have no idea how to do it but we are still expected to wait.
> How is that acceptable!
>
>> Finally, I have never said the arbitration issue *must* be solved
>> before converting to blkmq. Only that we should avoid performance
>> regressions, but that of course applies to whatever changes we do.
>
> Then there is no problem in queuing up the CQE patches now!

Either you are not paying attention or just being grumpy.

So for the last time, I don't want to pick CQE, prior the existing mmc
block code has converted to blkmq.

End of discussion!

Kind regards
Uffe



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