linux-kernel - Re: [PATCH v3 5/5] alloc_tag: config to store page allocation tag refs in page flags

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Message-ID: <f2dada61-0e20-48b1-bb2f-9c9f02583005@redhat.com>
Date: Mon, 21 Oct 2024 17:49:35 +0200
From: David Hildenbrand <david@...hat.com>
To: Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>
Cc: John Hubbard <jhubbard@...dia.com>, Yosry Ahmed <yosryahmed@...gle.com>,
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Subject: Re: [PATCH v3 5/5] alloc_tag: config to store page allocation tag
 refs in page flags

On 21.10.24 17:41, Suren Baghdasaryan wrote:
> On Mon, Oct 21, 2024 at 8:34 AM Michal Hocko <mhocko@...e.com> wrote:
>>
>> On Mon 21-10-24 08:05:16, Suren Baghdasaryan wrote:
>> [...]
>>> Yeah, I thought about adding new values to "mem_profiling" but it's a
>>> bit complicated. Today it's a tristate:
>>>
>>> mem_profiling=0|1|never
>>>
>>> 0/1 means we disable/enable memory profiling by default but the user
>>> can enable it at runtime using a sysctl. This means that we enable
>>> page_ext at boot even when it's set to 0.
>>> "never" means we do not enable page_ext, memory profiling is disabled
>>> and sysctl to enable it will not be exposed. Used when a distribution
>>> has CONFIG_MEM_ALLOC_PROFILING=y but the user does not use it and does
>>> not want to waste memory on enabling page_ext.
>>>
>>> I can add another option like "pgflags" but then it also needs to
>>> specify whether we should enable or disable profiling by default
>>> (similar to 0|1 for page_ext mode). IOW we will need to encode also
>>> the default state we want. Something like this:
>>>
>>> mem_profiling=0|1|never|pgflags_on|pgflags_off
>>>
>>> Would this be acceptable?
>>
>> Isn't this overcomplicating it? Why cannot you simply go with
>> mem_profiling={0|never|1}[,$YOUR_OPTIONS]
>>
>> While $YOUR_OPTIONS could be compress,fallback,ponies and it would apply
>> or just be ignored if that is not applicable.
> 
> Oh, you mean having 2 parts in the parameter with supported options being:
> 
> mem_profiling=never
> mem_profiling=0
> mem_profiling=1
> mem_profiling=0,pgflags
> mem_profiling=1,pgflags
> 

That's also a viable solution indeed.

-- 
Cheers,

David / dhildenb