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[80.230.47.179]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a5c24d82asm164063795e9.7.2026.04.26.13.54.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 26 Apr 2026 13:54:41 -0700 (PDT) Date: Sun, 26 Apr 2026 16:54:35 -0400 From: "Michael S. Tsirkin" To: Matthew Wilcox Cc: linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , Vlastimil Babka , Brendan Jackman , Michal Hocko , Suren Baghdasaryan , Jason Wang , Andrea Arcangeli , Gregory Price , linux-mm@kvack.org, virtualization@lists.linux.dev, Johannes Weiner , Zi Yan , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Muchun Song , Oscar Salvador , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Hugh Dickins , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH RFC v3 01/19] mm: thread user_addr through page allocator for cache-friendly zeroing Message-ID: <20260426165330-mutt-send-email-mst@kernel.org> References: <9dd9deabd42801f3c344326991d1431c3d8db39d.1776808210.git.mst@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@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: On Fri, Apr 24, 2026 at 07:41:03PM +0100, Matthew Wilcox wrote: > On Tue, Apr 21, 2026 at 06:01:10PM -0400, Michael S. Tsirkin wrote: > > Thread a user virtual address from vma_alloc_folio() down through > > the page allocator to post_alloc_hook(). This is plumbing preparation > > for a subsequent patch that will use user_addr to call folio_zero_user() > > for cache-friendly zeroing of user pages. > > > > The user_addr is stored in struct alloc_context and flows through: > > vma_alloc_folio -> folio_alloc_mpol -> __alloc_pages_mpol -> > > __alloc_frozen_pages -> get_page_from_freelist -> prep_new_page -> > > post_alloc_hook > > I don't like this. I think we should instead lift the zeroing from > post_alloc_hook() to the callers of __alloc_frozen_pages(). can you and david agree somehow? I don't like being caught betweem maintainers like this. > I don't understand why you want to remove the double-zeroing of memory > when the user has asked for zero_on_alloc. They asked for stupid things, > let them bear the cost. it's just a side effect. I did not even test what effect it has. what I care about is the overhead with reporting.