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

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Message-ID: <ZGeiJhIo3J5atZHV@moria.home.lan>
Date:   Fri, 19 May 2023 12:21:58 -0400
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Song Liu <song@...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 Fri, May 19, 2023 at 07:14:14PM +0300, Mike Rapoport wrote:
> Unfortunately not because we still need to map the pages in the modules
> area which is essentially a subset of vmalloc address space.

Why wouldn't we be doing that once per 2 MB page?

>  
> > If I have time (hah! big if :) I'll see if I can cook up a patchset that
> > combines our two approaches over the weekend.
> 
> Now there is also an interest about unmapped allocations from KVM folks, so
> I might continue pursuing unmapped allocator, probably just without a new
> GFP flag and hooks into page allocator.

Cool - it does seem like a generally valuable capability :)