linux-kernel - Re: [RFC PATCH 0/5] add process_madvise() flags to modify behaviour

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Message-ID: <uhla5o5xqshcrihc5gpkqqyoplj7hxrbptp6prmwd2mh3ikw4m@m6apbkyfny6c>
Date: Thu, 22 May 2025 13:53:51 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: David Hildenbrand <david@...hat.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, Arnd Bergmann <arnd@...db.de>, 
	Christian Brauner <brauner@...nel.org>, linux-mm@...ck.org, linux-arch@...r.kernel.org, 
	linux-kernel@...r.kernel.org, SeongJae Park <sj@...nel.org>, 
	Usama Arif <usamaarif642@...il.com>
Subject: Re: [RFC PATCH 0/5] add process_madvise() flags to modify behaviour

On Thu, May 22, 2025 at 03:05:30PM +0200, David Hildenbrand wrote:
> On 21.05.25 19:39, Shakeel Butt wrote:
> > On Wed, May 21, 2025 at 05:49:15PM +0100, Lorenzo Stoakes wrote:
> > [...]
> > > > 
> > > > Please let's first get consensus on this before starting the work.
> > > 
> > > With respect Shakeel, I'll work on whatever I want, whenever I want.
> > 
> > I fail to understand why you would respond like that.
> 
> Relax guys ... :) Really nothing to be fighting about.

Agreed.

[...]

> 
> 
> To summarize my current view:
> 
> 1) ebpf: most people are are not a fan of that, and I agree, at least
>    for this purpose. If we were talking about making better *placement*
>    decisions using epbf, it would be a different story.

>From placement decisions, do you mean placement between memory
tiers/nodes or something else?

> 
> 2) prctl(): the unloved child, and I can understand why. Maybe now is
>    the right time to stop adding new MM things that feel weird in there.
>    Maybe we should already have done that with the KSM toggle (guess who
>    was involved in that ;) ).

At the moment systemd is the user I know of and I think it would very
easy to migrate it to whatever new thing we decide here.

> 
> 3) process_madvise(): I think it's an interesting extension, but
>    probably we should just have something that applies to the whole
>    address space naturally. At least my take for now.
> 
> 4) new syscall: worth exploring how it would look. I'm especially
>    interested in flag options (e.g., SET_DEFAULT_EXEC) and how we could
>    make them only apply to selected controls.

Were there any previous discussion on SET_DEFAULT_EXEC? First time I am
hearing about it.

Overall I agree with your assessment and thus I was requesting to at
least discuss the new syscall option as well.