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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> MIME-Version: 1.0 In-Reply-To: <8900872f-39e1-44ab-8440-e91ce3f0523a@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: WEpe1NE2S2KdJF1Cm4J_Xq-gFZo1nH1mEu72TgFgUac_1776180990 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: 997AF1C0006 X-Stat-Signature: o8i31iffxyu9aryuwb8ykogfqby7iwic X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1776180996-321206 X-HE-Meta: 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 ZyOqJxqt f8jXOpY3lbujGPNvjnu5Og7tXIrzE5E/LDlV9opinYMF+cBzFNtCsYCMyuvhJFdWwnpPleph6KA2aMaRJECj6SdCZt4eQpxBVxSM1KnCog/12gBc9zeWCwoegq5n553r6BucvZqlr19Sh9NsWU1JcyCRnX/skjKKnWoBtElg1IVcI5dNdD8czi8eb+7eoONuQBc5dusmwXG25QHgLzHkm9/8nYsG+FVbo8cY+flDYFSumVc6JH3vkc2iORYvYhIH3sYBJZyVYsHxWVJqbDgFmnJ4208QnsVhai5yTsVjTpwVjePWOOt6mPw+NmdBJkoJ6okBwMma+Z1FQv43BwobgbuMUqgIvYdrcOyGQIxOYNph+ztX3hUDuEHVGBtQXGIps2KTa Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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