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

[Suren Baghdasaryan <surenb@google.com>]

On Mon, Oct 21, 2024 at 8:57 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Mon 21-10-24 08:41:00, Suren Baghdasaryan wrote:
> > On Mon, Oct 21, 2024 at 8:34 AM Michal Hocko <mhocko@suse.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.
>
> yes. I would just not call it pgflags because that just doesn't really
> tell what the option is to anybody but kernel developers. You could also
> have an option to override the default (disable profiling) failure strategy.

Ok, how about "compressed" instead? Like this:

mem_profiling=0,compressed

> --
> Michal Hocko
> SUSE Labs