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[80.230.25.21]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d7400708dsm9145343f8f.25.2026.04.12.15.50.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Apr 2026 15:50:56 -0700 (PDT) Date: Sun, 12 Apr 2026 18:50:54 -0400 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Andrew Morton , David Hildenbrand , 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 Subject: [PATCH RFC 5/9] mm: skip zeroing in alloc_anon_folio for pre-zeroed pages Message-ID: <56ae30d7f080b089e4fdc93c4d6e2353a9e0123a.1776033771.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 Use __GFP_PREZEROED and folio_test_clear_prezeroed() to skip folio_zero_user() in the mTHP anonymous page allocation path when the page is already zeroed. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- mm/memory.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 07778814b4a8..2f61321a81fd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5176,7 +5176,7 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) goto fallback; /* Try allocating the highest of the remaining orders. */ - gfp = vma_thp_gfp_mask(vma); + gfp = vma_thp_gfp_mask(vma) | __GFP_PREZEROED; while (orders) { addr = ALIGN_DOWN(vmf->address, PAGE_SIZE << order); folio = vma_alloc_folio(gfp, order, vma, addr); @@ -5194,7 +5194,8 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf) * that the page corresponding to the faulting address * will be hot in the cache after zeroing. */ - if (user_alloc_needs_zeroing()) + if (user_alloc_needs_zeroing() && + !folio_test_clear_prezeroed(folio)) folio_zero_user(folio, vmf->address); return folio; } -- MST