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[80.230.25.21]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d6f4bf2b4sm12414218f8f.20.2026.04.12.15.50.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Apr 2026 15:51:00 -0700 (PDT) Date: Sun, 12 Apr 2026 18:50:57 -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 , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang Subject: [PATCH RFC 6/9] mm: skip zeroing in vma_alloc_anon_folio_pmd for pre-zeroed pages Message-ID: <7287019f2665c85a7a7fb5ffc25d7203bdfa9a9c.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 PMD THP anonymous page allocation path when the page is already zeroed. Signed-off-by: Michael S. Tsirkin Assisted-by: Claude:claude-opus-4-6 --- mm/huge_memory.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 8e2746ea74ad..3b9b53fad0f1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1256,7 +1256,7 @@ EXPORT_SYMBOL_GPL(thp_get_unmapped_area); static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma, unsigned long addr) { - gfp_t gfp = vma_thp_gfp_mask(vma); + gfp_t gfp = vma_thp_gfp_mask(vma) | __GFP_PREZEROED; const int order = HPAGE_PMD_ORDER; struct folio *folio; @@ -1285,7 +1285,7 @@ static struct folio *vma_alloc_anon_folio_pmd(struct vm_area_struct *vma, * make sure 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, addr); /* * The memory barrier inside __folio_mark_uptodate makes sure that -- MST