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: <ZxZ0eh95AfFcQSFV@tiehlicka>
Date: Mon, 21 Oct 2024 17:34:18 +0200
From: Michal Hocko <mhocko@...e.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: David Hildenbrand <david@...hat.com>,
	John Hubbard <jhubbard@...dia.com>,
	Yosry Ahmed <yosryahmed@...gle.com>, akpm@...ux-foundation.org,
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Subject: Re: [PATCH v3 5/5] alloc_tag: config to store page allocation tag
 refs in page flags

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. 
-- 
Michal Hocko
SUSE Labs