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[80.230.25.21]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488ede1e826sm119796545e9.6.2026.04.14.08.36.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Apr 2026 08:36:28 -0700 (PDT) Date: Tue, 14 Apr 2026 11:36:25 -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 Subject: Re: [PATCH RFC 2/9] mm: page_reporting: skip redundant zeroing of host-zeroed reported pages Message-ID: <20260414113505-mutt-send-email-mst@kernel.org> References: <2155527a-e077-4b71-80ee-d735f9984f60@kernel.org> <20260413163233-mutt-send-email-mst@kernel.org> <244c9779-b4a5-4d0f-9eb9-ef0ec873e0f6@kernel.org> <20260414062015-mutt-send-email-mst@kernel.org> <8900872f-39e1-44ab-8440-e91ce3f0523a@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <8900872f-39e1-44ab-8440-e91ce3f0523a@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4oWpm4cNdQ3tmTHOLNEqiPoDltLZd0Z9qqLkVoLkqm0_1776180990 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Tue, Apr 14, 2026 at 05:32:16PM +0200, David Hildenbrand (Arm) wrote: > On 4/14/26 12:22, Michael S. Tsirkin wrote: > > On Tue, Apr 14, 2026 at 11:18:02AM +0200, David Hildenbrand (Arm) wrote: > >> On 4/13/26 22:35, Michael S. Tsirkin wrote: > >>> > >>> > >>> So here's an only alternative I see: a page flag for when page is in > >>> buddy and a new "prezero" bool that we have to propagate everywhere > >>> else. This is a patch on top. More elegant? Please tell me if you prefer that. > >>> If yes I will squash it into the appropriate patches. > >> > >> I'd be interesting to know how this would look without the GFP flag, > >> when we don't have to leak any of this out of the buddy. > >> > >> -- > >> Cheers, > >> > >> David > > > > But the zeroing takes place outside of the buddy now, it's more > > "reporting" than "leaking". > > Exposing some buddy internals using questionable GFP flags, however you > want to call that hack ;) > > > > > You mean, moving the zeroing into buddy? > > Yes. Such that it doesn't really matter how we maintain this information > internally. A page flag is probably still nicer for that purpose. OK, sure. Let me just finish testing, and I will post. -- MST