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[100.36.248.188]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-5148e68a963sm123339831cf.13.2026.05.12.09.32.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 09:32:22 -0700 (PDT) Date: Tue, 12 May 2026 12:32:20 -0400 From: Gregory Price To: "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: Re: [PATCH resend v6 20/30] mm: page_alloc: clear PG_zeroed on buddy merge if not both zero Message-ID: References: <20260512115805-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512115805-mutt-send-email-mst@kernel.org> X-Rspam-User: X-Rspamd-Queue-Id: 89D54140007 X-Rspamd-Server: rspam06 X-Stat-Signature: ojsmbtt6i8hmdecihgkbgcq4qdy9py9a X-HE-Tag: 1778603544-439847 X-HE-Meta: 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 jWPfqcVm 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, May 12, 2026 at 11:58:27AM -0400, Michael S. Tsirkin wrote: > On Tue, May 12, 2026 at 11:56:02AM -0400, Gregory Price wrote: > > On Mon, May 11, 2026 at 05:03:35AM -0400, Michael S. Tsirkin wrote: > > > When two buddy pages merge in __free_one_page(), preserve > > > PG_zeroed on the merged page only if both buddies have the > > > flag set. Otherwise clear it. > > > > > > The merged page would inherit PG_zeroed, and a later __GFP_ZERO > > > allocation would skip zeroing stale data in the non-zero half. > > > > > > Signed-off-by: Michael S. Tsirkin > > > Assisted-by: Claude:claude-opus-4-6 > > > Assisted-by: cursor-agent:GPT-5.4-xhigh > > > --- > > > mm/page_alloc.c | 15 ++++++++++++++- > > > 1 file changed, 14 insertions(+), 1 deletion(-) > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index bd3b909cacdf..d70c9ba6b329 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -940,10 +940,14 @@ static inline void __free_one_page(struct page *page, > > > unsigned long buddy_pfn = 0; > > > unsigned long combined_pfn; > > > struct page *buddy; > > > + bool buddy_zeroed; > > > + bool page_zeroed; > > > > If you want to play some code golf, i think you can get away with a > > single bool here: > > > > bool zeroed; > > zeroed = PageZeroed(buddy); > > zeroed &= PageZeroed(page); > > > > if (zeroed) > > __SetPageZeroed(page); > > > > ~Gregory > > Does it matter? It makes my head hurt. > Less code generally means less bugs, but this is more style nits than anything. Either way Reviewed-by: Gregory Price ~Gregory