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

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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!
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