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b=H49B90HSTsjTYtBoUnW/LU4uL0T1hght3SqZoXNwwASlW55bQNW1CinjwhB/prcmu iUoxWppmLaa5HNplX4vWLbPVkAG6YuzUv4H6BG/3/HxAKWJ3DWieR4Mz+tcKIBF0ir NQVLIl7RSw4sDuGvQsRj0rCqRGAXZ/g283OZKWIiYR8ecmEAoPRGpPidbnDOkdFGB8 TeW7p5S3BktQ3dneRvFiYg43r1Fnj+DAgk9v+5LCHzStBuN4DbHRIum3ms39Cckv9g aWohmQHz6h3UAMFJzdhnOZ0KvM+87mJQ2NFc4QKpRpimGJymmCS44YVNbGkyc5H6Fu g9jRKgCFBGhxw== Date: Tue, 29 Oct 2024 18:35:30 +0200 From: Mike Rapoport To: David Rientjes Cc: James Gowans , Dave Hansen , David Hildenbrand , Matthew Wilcox , Mike Rapoport , Pasha Tatashin , Peter Xu , Alexander Graf , Ashish Kalra , Tom Lendacky , David Woodhouse , Anthony Yznaga , Jason Gunthorpe , Andrew Morton , Frank van der Linden , Vipin Sharma , David Matlack , Steve Rutherford , Erdem Aktas , Alper Gun , Vishal Annapurve , Ackerley Tng , Sagi Shahar , linux-mm@kvack.org, kexec@lists.infradead.org Subject: Re: Pmemfs/guestmemfs discussion recap and open questions Message-ID: References: <5b6613bc-beef-79e6-62ed-23de4dfafe51@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5b6613bc-beef-79e6-62ed-23de4dfafe51@google.com> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: A0A7A180020 X-Stat-Signature: oxkpj3b44thue1oxszdahxbuc5jhjsbk X-HE-Tag: 1730219952-591590 X-HE-Meta: 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 3ifsQ0S7 KedYMOuTthKaDqlqU4mrFHgB4varMccZdBbNYflPu8WO8U2h6JblVXDI1t94wo5goqTwFg67UvS9blxNse3kkSPtuEHp+Yp/MsVMdcNJxm2Q+cYW3WQSew2rfm4k2d4h65iplu6aB7MmEHBCPMmJCP8o4EBWIrj83OtGqUARIz6Cju6KsjXzqZECJ8brLFzNVzLFvT9s/HPxu5rgeSISj16qmyfFPp2dyYR93/5qRCSSYkS2FJ4Vs0gb6PxEbK7tP9Vp0zdinLbrbDRq0KALcY1IvAUkncVOGIV3ONzoXRmkQXEFF8/Cqo2HXu2P6ieWKPR6BQUolx8Vzb+k= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi David, On Fri, Oct 25, 2024 at 11:07:27PM -0700, David Rientjes wrote: > On Wed, 16 Oct 2024, David Rientjes wrote: > > > ----->o----- > > My takeaway: based on the feedback that was provided in the discussion: > > > > - we need an allocator abstraction for persistent memory that can return > > memory with various characteristics: 1GB or not, kernel direct map or > > not, HVO or not, etc. > > > > - built on top of that, we need the ability to carve out very large > > ranges of memory (cloud provider use case) with NUMA awareness on the > > kernel command line > > > > Following up on this, I think this physical memory allocator would also be > possible to use as a backend for hugetlb. Hopefully this would be an > allocator that would be generally useful for multiple purposes, something > like a mm/phys_alloc.c. Can you elaborate on this? mm/page_alloc.c already allocates physical memory :) Or you mean an allocator that will deal with memory carved out from what page allocator manages? > Frank van der Linden may also have thoughts on the above? > > > - we also need the ability to be able to dynamically resize this or > > provide hints at allocation time that memory must be persisted across > > kexec to support the non-cloud provider use case > > > > - we need a filesystem abstraction that map memory of the type that is > > requested, including guest_memfd and then deal with all the fun of > > multitenancy since it would be drawing from a finite per-NUMA node > > pool of persistent memory > > > > - absolutely critical to this discussion is defining what is the core > > infrastructure that is required for a generally acceptable solution > > and then what builds off of that to be more special cased (like the > > cloud provider use case or persistent tmpfs use case) > > > > We're looking to continue that discussion here and then come together > > again in a few weeks. > > > > We'll be looking to schedule some more time to talk about this topic in > the Wednesday, November 13 instance of the Linux MM Alignment Session. > > After that, I think it would be quite useful to break out the set of > people that are interested in persisting guest memory across kexec and KHO > into a separate series to accelerate discussion and next stpes. Getting > the requirements and design locked down are critical, so happy to > facilitate that to any extent possible and welcome everybody interested in > discussing it. > > James, for the guestmemfs discussions, would this work for you? > > Alexander, same question for you regarding the KHO work? > > It's a global community, so the timing won't work for eveyrbody. We'd > plan on sending out summaries of these discussions, such as in this email, > to solicit feedback and ideas from everybody. > > If you're not on the To: or Cc: list already, please email me separatel if > you're interested in participating and then we can find a regular time. > > This is exciting! > -- Sincerely yours, Mike.