Date: Tue, 13 Feb 2024 23:57:29 +0100
From: David Hildenbrand <david@...hat.com>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
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Subject: Re: [PATCH v3 00/35] Memory allocation profiling

On 13.02.24 23:50, Kent Overstreet wrote:
> On Tue, Feb 13, 2024 at 11:48:41PM +0100, David Hildenbrand wrote:
>> On 13.02.24 23:30, Suren Baghdasaryan wrote:
>>> On Tue, Feb 13, 2024 at 2:17 PM David Hildenbrand <david@...hat.com> wrote:
>>>>
>>>> On 13.02.24 23:09, Kent Overstreet wrote:
>>>>> On Tue, Feb 13, 2024 at 11:04:58PM +0100, David Hildenbrand wrote:
>>>>>> On 13.02.24 22:58, Suren Baghdasaryan wrote:
>>>>>>> On Tue, Feb 13, 2024 at 4:24 AM Michal Hocko <mhocko@...e.com> wrote:
>>>>>>>>
>>>>>>>> On Mon 12-02-24 13:38:46, Suren Baghdasaryan wrote:
>>>>>>>> [...]
>>>>>>>>> We're aiming to get this in the next merge window, for 6.9. The feedback
>>>>>>>>> we've gotten has been that even out of tree this patchset has already
>>>>>>>>> been useful, and there's a significant amount of other work gated on the
>>>>>>>>> code tagging functionality included in this patchset [2].
>>>>>>>>
>>>>>>>> I suspect it will not come as a surprise that I really dislike the
>>>>>>>> implementation proposed here. I will not repeat my arguments, I have
>>>>>>>> done so on several occasions already.
>>>>>>>>
>>>>>>>> Anyway, I didn't go as far as to nak it even though I _strongly_ believe
>>>>>>>> this debugging feature will add a maintenance overhead for a very long
>>>>>>>> time. I can live with all the downsides of the proposed implementation
>>>>>>>> _as long as_ there is a wider agreement from the MM community as this is
>>>>>>>> where the maintenance cost will be payed. So far I have not seen (m)any
>>>>>>>> acks by MM developers so aiming into the next merge window is more than
>>>>>>>> little rushed.
>>>>>>>
>>>>>>> We tried other previously proposed approaches and all have their
>>>>>>> downsides without making maintenance much easier. Your position is
>>>>>>> understandable and I think it's fair. Let's see if others see more
>>>>>>> benefit than cost here.
>>>>>>
>>>>>> Would it make sense to discuss that at LSF/MM once again, especially
>>>>>> covering why proposed alternatives did not work out? LSF/MM is not "too far"
>>>>>> away (May).
>>>>>>
>>>>>> I recall that the last LSF/MM session on this topic was a bit unfortunate
>>>>>> (IMHO not as productive as it could have been). Maybe we can finally reach a
>>>>>> consensus on this.
>>>>>
>>>>> I'd rather not delay for more bikeshedding. Before agreeing to LSF I'd
>>>>> need to see a serious proposl - what we had at the last LSF was people
>>>>> jumping in with half baked alternative proposals that very much hadn't
>>>>> been thought through, and I see no need to repeat that.
>>>>>
>>>>> Like I mentioned, there's other work gated on this patchset; if people
>>>>> want to hold this up for more discussion they better be putting forth
>>>>> something to discuss.
>>>>
>>>> I'm thinking of ways on how to achieve Michal's request: "as long as
>>>> there is a wider agreement from the MM community". If we can achieve
>>>> that without LSF, great! (a bi-weekly MM meeting might also be an option)
>>>
>>> There will be a maintenance burden even with the cleanest proposed
>>> approach.
>>
>> Yes.
>>
>>> We worked hard to make the patchset as clean as possible and
>>> if benefits still don't outweigh the maintenance cost then we should
>>> probably stop trying.
>>
>> Indeed.
>>
>>> At LSF/MM I would rather discuss functonal
>>> issues/requirements/improvements than alternative approaches to
>>> instrument allocators.
>>> I'm happy to arrange a separate meeting with MM folks if that would
>>> help to progress on the cost/benefit decision.
>> Note that I am only proposing ways forward.
>>
>> If you think you can easily achieve what Michal requested without all that,
>> good.
> 
> He requested something?
> 

This won't get merged without acks from MM people.

-- 
Cheers,

David / dhildenb

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