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Howlett" , Mike Rapoport , Johannes Weiner , Zi Yan Subject: Re: [PATCH RFC 3/9] mm: add __GFP_PREZEROED flag and folio_test_clear_prezeroed() Message-ID: <20260413180303-mutt-send-email-mst@kernel.org> References: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: okCpBksTLr-HfWMilINFlnQ6FUNyeNPMvEyLU3O-6r4_1776117975 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: 8AF9C80004 X-Stat-Signature: wur5pxq1dyzaqxr6rodaz1sjwudegojx X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1776117978-823624 X-HE-Meta: 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 A3QcdQis i8l5GfaYf0khM3ePd1Nk9tVf33d5z4UeTTs8GS14YXNBLWlvoPdLo0IBfhucu3SVMqCjXh8zK0FYqGVO3Bs6eTQ8fk6KZCyfr4ikOiPcJOip2ROfqYKB1ifkaVFr6DAITVi0jRKWXWb8r1YQa+5qj9LZzlkt3Ub8nvdYQxzzEAyXhit/7bwTGU9VmWeOP8WLNIDPE6J5+CmbVeyRvndodd9Ua0h+VykLlc0cXck/psdOT+QLHbgcXt5ISgNPNV32Xs1qPohZzYnRfERwQkrX2TUHyvqo30oNAxziwSUbxUDK7Rdk5fMO+yLShivFoPwvrnohbQ7YzICwW/Fp9oGkoGeKlznmficEUqTlgMy8PBsmyhOz+COaNE7a+yzouzQv4Hk89 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Apr 13, 2026 at 11:05:40AM +0200, David Hildenbrand (Arm) wrote: ... > (2) Use a dedicated allocation interface for user pages in the buddy. > > I hate the whole user_alloc_needs_zeroing()+folio_zero_user() handling. > > It shouldn't exist. We should just be passing GFP_ZERO and let the buddy handle > all that. > > > For example, vma_alloc_folio() already gets passed the address in. > > Pass the address from vma_alloc_folio_noprof()->folio_alloc_noprof(), and let > folio_alloc_noprof() use a buddy interface that can handle it. > > Imagine if we had a alloc_user_pages_noprof() that consumes an address. It could just > do what folio_zero_user() does, and only if really required. > > The whole user_alloc_needs_zeroing() could go away and you could just handle the > pre-zeroed optimization internally. I looked at this a bit, and I think the issue is that the buddy allocator doesn't do the arch-specific cache handling. So allocating it is a fundamentally different thing from GFP_ZERO which is "zero a kernel address range". So I don't get how you want to do it. > > -- > Cheers, > > David