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[80.230.25.45]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45d9e768072sm56994075f8f.5.2026.05.20.15.23.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 May 2026 15:23:27 -0700 (PDT) Date: Wed, 20 May 2026 18:23:23 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?utf-8?B?UMOpcmV6?= , 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 , Gregory Price , 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: [PATCH v8 34/37] mm: page_alloc: skip kernel_init_pages for FPI_ZEROED when safe Message-ID: <86f98d31a9b7989c699bad2e7f1fcc977a58d0a1.1779315441.git.mst@redhat.com> References: 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: X-Mailer: git-send-email 2.27.0.106.g8ac3dc51b1 X-Mutt-Fcc: =sent In __free_pages_prepare(), when FPI_ZEROED is set the page is already known to be zero. We can skip kernel_init_pages() if page poisoning is not enabled (because poison would overwrite the zeroes). This avoids redundant zeroing work when freeing pages that are already known to contain all zeros. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- mm/page_alloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 399e2038dcd9..90a92be96ebf 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1447,7 +1447,14 @@ __always_inline bool __free_pages_prepare(struct page *page, if (kasan_has_integrated_init()) init = false; } - if (init) + /* + * Skip redundant zeroing when the page is already known-zero + * (FPI_ZEROED) and page poisoning did not overwrite it. + * When page_poisoning is enabled, kernel_poison_pages above + * wrote PAGE_POISON (0xAA), so we must re-zero. + */ + if (init && !((fpi_flags & FPI_ZEROED) && + !page_poisoning_enabled_static())) kernel_init_pages(page, 1 << order); /* -- MST