linux-kernel - Re: [RFC PATCH 1/5] mm: intorduce __GFP_UNMAPPED and unmapped

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Message-ID: <CAPhsuW5BbbxinaH2aO=2Wa0aSQ3pkNwvnrgJv7fG4QcPr_j7+Q@mail.gmail.com>
Date:   Thu, 18 May 2023 10:00:39 -0700
From:   Song Liu <song@...nel.org>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     Mike Rapoport <rppt@...nel.org>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: Re: [RFC PATCH 1/5] mm: intorduce __GFP_UNMAPPED and unmapped_alloc()

On Thu, May 18, 2023 at 9:48 AM Kent Overstreet
<kent.overstreet@...ux.dev> wrote:
>
> On Thu, May 18, 2023 at 09:33:20AM -0700, Song Liu wrote:
> > I am working on patches based on the discussion in [1]. I am planning to
> > send v1 for review in a week or so.
>
> Hey Song, I was reviewing that thread too,
>
> Are you taking a different approach based on Thomas's feedback? I think
> he had some fair points in that thread.

Yes, the API is based on Thomas's suggestion, like 90% from the discussions.

>
> My own feeling is that the buddy allocator is our tool for allocating
> larger variable sized physically contiguous allocations, so I'd like to
> see something based on that - I think we could do a hybrid buddy/slab
> allocator approach, like we have for regular memory allocations.

I am planning to implement the allocator based on this (reuse
vmap_area logic):

https://lore.kernel.org/linux-mm/20221107223921.3451913-2-song@kernel.org/

Thanks,
Song

>
> I started on a slab allocator for executable memory allocations the
> other day (very minimal, but tested it for bcachefs and it works).
>
> But I'd love to hear more about your current approach as well.
>
> Cheers,
> Kent