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Tsirkin" To: Kevin Loughlin Cc: "David Hildenbrand (Arm)" , Jason Wang , Eugenio =?iso-8859-1?Q?P=E9rez?= , Xuan Zhuo , Ard Biesheuvel , Kiryl Shutsemau , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Tom Lendacky , Ashish Kalra , Michael Roth , Rick Edgecombe , Andrew Morton , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Alexander Duyck , virtualization@lists.linux.dev, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Sidharth Telang , Punit Salian , Peter Gonda , Ackerley Tng , Jacky Li , Steve Rutherford , David Skidmore Subject: Re: [PATCH 00/13] virtio_balloon, efi/unaccepted: support memory ballooning and free page reporting in CoCo guests Message-ID: <20261028145316-mutt-send-email-mst@kernel.org> References: <20261027025616.1632690-1-kevinloughlin@google.com> <279a92da-772c-422b-8047-ad37dbae211f@kernel.org> X-Archived-By: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 6B3XZZkUxSFKLY8wAPBdSKh8kODvztfdJxEoRoOtIaw_1793213667 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 68C108000E X-Stat-Signature: 59nbeijpa85qsao8mjo8a793oh6bm3up X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793213670-367956 X-HE-Meta: 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 D5pIawX8 uDqM88WFZ4Jw4fD36SHSiEK81S5r2B53IKJU/MQIIDMKdLjD0eKgiTshbMSBn5ZtCQhJPkuvgRkGnKqZsuJdHBqAxUweoXdNS6OrIjd5U7x2CDDYJNKq5kpms8RNoIHkEAUBWafNtAJaRMLzpcvs3OKaqwfETPasFnGR57x1E9folTbAfFZX3CfrpA/BwwHJFT1QXH51SAGVqWWadYDg9+I2FBEs4fUlyrxqMahcJkBIBByvdcSFkMxOlD12MSE0KxfNcSo1AJvI27TONyiL0jp19hjveMVfge7zlxkpmldXho9xracwdn7s2L36HhGB/e4zwSOqjM4vbOPKmMTjhNgVbAxHje98dXcEoA6QPQk6saHx/X98Gl16gOar8+s2F0OqCK3ddug+pv38CQMqe2JgkTQQW9nX4wKtOjMdtHytJx4wB7Is6tvJQTw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Oct 28, 2026 at 11:12:47AM -0700, Kevin Loughlin wrote: > On Wed, Oct 28, 2026 at 2:01 AM David Hildenbrand (Arm) > wrote: > > > > On 10/27/26 03:56, Kevin Loughlin wrote: > > > > > [...] > > > > > mm/page_alloc.c | 248 ++++++++++++----- > > > > This diff stat should give you a good indication why this series is not acceptable. > > Got it. I will keep that in mind going forward, especially if I end up > attempting a v2 that simplifies things. > > On that note, I believe the majority of the bloat in mm/page_alloc.c > comes from... > 1. supporting the legacy inflate/deflate option > 2. introducing support for various page sizes to be unaccepted > > (1) I can get rid of by dropping the inflate/deflate option, which I > think makes sense given free page reporting should be sufficient to > enable dynamic guest downsizing in cooperative scenarios. > > (2) becomes simpler in part just by doing (1). For further > simplification, we could potentially restrict free page reporting for > CoCo guests to the current 4 MB MAX_PAGE_ORDER instead of supporting > any order 2 MB and up. There's a trade-off here for reporting > effectiveness under fragmentation, but perhaps support for 4 MB only > (and its relative simplicity) could be acceptable? Especially since we > would then maintain the invariant that all pages on the unaccepted > list are MAX_PAGE_ORDER? I'm not sure what is meant here. But if a lot of memory is free and it gets merged beyond MAX_PAGE_ORDER and then it's not reported, that's counterintuitive. > If I can sufficiently simplify the changes (especially in mm/), do you > potentially see a path forward purely for the free page reporting > aspect of this (dropping inflate/deflate)? > > Thank you for taking the time to review, David!