linux-kernel - Re: [RFC PATCH 00/30] Code tagging framework and applications

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Message-ID: <20220901142937.vsnq62e6gqytyth2@moria.home.lan>
Date:   Thu, 1 Sep 2022 10:29:37 -0400
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mel Gorman <mgorman@...e.de>,
        Suren Baghdasaryan <surenb@...gle.com>,
        akpm@...ux-foundation.org, mhocko@...e.com, vbabka@...e.cz,
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Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications

On Thu, Sep 01, 2022 at 09:00:17AM +0200, Peter Zijlstra wrote:
> On Wed, Aug 31, 2022 at 11:19:48AM +0100, Mel Gorman wrote:
> 
> > It's also unclear *who* would enable this. It looks like it would mostly
> > have value during the development stage of an embedded platform to track
> > kernel memory usage on a per-application basis in an environment where it
> > may be difficult to setup tracing and tracking. Would it ever be enabled
> > in production? 
> 
> Afaict this is developer only; it is all unconditional code.
> 
> > Would a distribution ever enable this? 
> 
> I would sincerely hope not. Because:
> 
> > If it's enabled, any overhead cannot be disabled/enabled at run or
> > boot time so anyone enabling this would carry the cost without never
> > necessarily consuming the data.
> 
> this.

We could make it a boot parameter, with the alternatives infrastructure - with a
bit of refactoring there'd be a single function call to nop out, and then we
could also drop the elf sections as well, so that when built in but disabled the
overhead would be practically nil.