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[80.230.25.21]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-38ecb716751sm32721331fa.29.2026.04.21.06.16.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Apr 2026 06:17:02 -0700 (PDT) Date: Tue, 21 Apr 2026 09:16:56 -0400 From: "Michael S. Tsirkin" To: "David Hildenbrand (Arm)" Cc: linux-kernel@vger.kernel.org, Andrew Morton , Vlastimil Babka , Brendan Jackman , Michal Hocko , Suren Baghdasaryan , Jason Wang , Andrea Arcangeli , linux-mm@kvack.org, virtualization@lists.linux.dev, Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Johannes Weiner , Zi Yan , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu Subject: Re: [PATCH RFC v2 17/18] mm: add free_frozen_pages_hint and put_page_hint APIs Message-ID: <20260421091546-mutt-send-email-mst@kernel.org> References: <5f76af6e-9818-42ea-a305-c0fc1d920dca@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5f76af6e-9818-42ea-a305-c0fc1d920dca@kernel.org> On Tue, Apr 21, 2026 at 12:56:00PM +0200, David Hildenbrand (Arm) wrote: > On 4/20/26 14:51, Michael S. Tsirkin wrote: > > Add free_frozen_pages_hint(page, order, hints) to free a page > > while marking it as pre-zeroed when PGHINT_ZEROED is set. > > The PG_zeroed flag is set after __free_pages_prepare so it > > survives on the free list. > > > > Add __folio_put_hint(), folio_put_hint(), and put_page_hint() > > wrappers for the put_page path. > > Can we defer that change? We can - it's a dependency of the balloon deflate, which you asked me to implement. I'm more interested in reporting, myself. > Putting a page with a hint, when there might still be other users of the > page is a weird interface. The hint is just ignored in this case. > In the long term, all balloon pages (PG_offline pages) will be frozen > pages, and definitely not folios. > > Frozen pages don't have a refcount. > > It would then be sufficient to have the single owner of the page call > something like free_frozen_zeroed_page(). > > Now, to convert balloon pages to be frozen requires some more work, > primarily to balloon migration handling, unfortunately. I have it on my > todo list, but it will take a while. > > -- > Cheers, > > David