linux-kernel - Re: [PATCH v1 05/11] mm: convert VM_PFNMAP tracking to pfnmap_track() + pfnmap

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Message-ID: <f08118b3-0736-4a5d-b780-8e3d88f45c02@lucifer.local>
Date: Mon, 28 Apr 2025 20:37:12 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Peter Xu <peterx@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-trace-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tursulin@...ulin.net>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>
Subject: Re: [PATCH v1 05/11] mm: convert VM_PFNMAP tracking to
 pfnmap_track() + pfnmap_untrack()

On Mon, Apr 28, 2025 at 07:23:18PM +0200, David Hildenbrand wrote:
> On 28.04.25 18:24, Peter Xu wrote:
> > On Mon, Apr 28, 2025 at 06:16:21PM +0200, David Hildenbrand wrote:
> > > > Probably due to what config you have.  E.g., when I'm looking mine it's
> > > > much bigger and already consuming 256B, but it's because I enabled more
> > > > things (userfaultfd, lockdep, etc.).
> > >
> > > Note that I enabled everything that you would expect on a production system
> > > (incld. userfaultfd, mempolicy, per-vma locks), so I didn't enable lockep.
> >
> > I still doubt whether you at least enabled userfaultfd, e.g., your previous
> > paste has:
> >
> >    struct vm_userfaultfd_ctx  vm_userfaultfd_ctx;   /*   176     0 */
> >
> > Not something that matters.. but just in case you didn't use the expected
> > config file you wanted to use..
>
> You're absolutely right. I only briefly rechecked for this purpose here on
> my notebook, and only looked for the existence of members, not expecting
> that we have confusing stuff like vm_userfaultfd_ctx.
>
> I checked again and the size stays at 192 with allyesconfig and then
> disabling debug options.

I think a reasonable case is everything on, except CONFIG_DEBUG_LOCK_ALLOC and I
don't care about nommu.

So:

CONFIG_PER_VMA_LOCK
CONFIG_SWAP
CONFIG_MMU (exclude the nommu vm_region field)
CONFIG_NUMA
CONFIG_NUMA_BALANCING
CONFIG_PER_VMA_LOCK
CONFIG_ANON_VMA_NAME
__HAVE_PFNMAP_TRACKING

So to be clear - allyesconfig w/o debug gives us this yes? And we don't add a
cache line? In which case all good :)


>
> --
> Cheers,
>
> David / dhildenb
>