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: <CAJuCfpGHKHJ_6xN4Ur4pjLgwTQ2QLkbWuAOhQQPinXNQVONxEA@mail.gmail.com>
Date: Mon, 21 Oct 2024 08:41:00 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Michal Hocko <mhocko@...e.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, 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

Did I understand correctly? If so then yes, this should work.

> --
> Michal Hocko
> SUSE Labs