From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1A530372ED6; Tue, 7 Jul 2026 17:09:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783444198; cv=none; b=oACstvpdT9IUoMJ+2hLWiP2WpghKkKrNmQajr6qrvVwBx78sSfrZ5N1+RZaKCtsAg5tIe8h9mY2HceyTpI1HHvjTkBj6YUocrknpZk35wjyxFKYUnE7Fs/kZsk6PCQBbRKJbPMmbyXTLpipNlMTSJPuCv9h9w9T+nNef6Tf/RuA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783444198; c=relaxed/simple; bh=Fli7YaSv2y6c6B2aCq4qlf+CIVVBRtRvVhuHOeOvDso=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ooNgo+30wL1/BbNezwdRM1agTfceoId5Zy2IViZiQrh0ropWFMVFkG3qPAZF0ltSZ+10jiVq5C9QgevAHKhAdEloF5eB6Oa/jnmcwGiHFz72xZbWMfb8mgw20UIV1ovSNhkB+bYOQLsz+K4Rwtttcse+S1xEvFIOojgzKnSV/Ao= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ilfmc06F; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ilfmc06F" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 84A401F000E9; Tue, 7 Jul 2026 17:09:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783444196; bh=6CUF4r7uPib5/E2O+eq3hGHhL62QsV+tEaoDwEyllTY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ilfmc06FAFeATNBCfn3m2SaaaswmEuje9O4YPqE8sB9iRfOk/k8OX0VfmqDNRhP6F qm33s5+R7gsznyaFV/hM/pgRlfTDt3Z5jY6ANbJ7DBq5ynoVzGPdeFfGkXQP4pXSrB nWYyaG7n4i/eZatWysf8ih7R/aI/s3c1kJKNe7LDPMlBRhSSK5Ld4oVqd7IEFI4TLX 7Rp0AfrrEN8+4u0LSC6IFY366eDcJHezNpreBLRis6DlGPQK9ZkiLGZKI9RbUnWxA1 XuS7ffBN/zsdFdZHlfNUkcXDKGYn3JQ0nX7QDgtQcuuTL7P8NC8klsHAiXAkzBvuVn k6Dxp4ektc7ug== Message-ID: <66e8d008-5eaf-4a9a-9cca-e9b2bd8c9f9a@kernel.org> Date: Tue, 7 Jul 2026 19:09:42 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 00/13] mm: rework anon_vma and remove anon_vma_chain To: wangtao , "akpm@linux-foundation.org" , "catalin.marinas@arm.com" , "will@kernel.org" , "tglx@kernel.org" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "x86@kernel.org" , "willy@infradead.org" , "sj@kernel.org" , "kees@kernel.org" , "luizcap@redhat.com" , "zhangjiao2@cmss.chinamobile.com" , "kas@kernel.org" , "ljs@kernel.org" Cc: "hpa@zytor.com" , "liam@infradead.org" , "vbabka@kernel.org" , "rppt@kernel.org" , "surenb@google.com" , "mhocko@suse.com" , "jack@suse.cz" , "riel@surriel.com" , "harry@kernel.org" , "jannh@google.com" , "jgg@ziepe.ca" , "jhubbard@nvidia.com" , "peterx@redhat.com" , "ziy@nvidia.com" , "baolin.wang@linux.alibaba.com" , "npache@redhat.com" , "ryan.roberts@arm.com" , "dev.jain@arm.com" , "baohua@kernel.org" , "lance.yang@linux.dev" , "xu.xin16@zte.com.cn" , "chengming.zhou@linux.dev" , "muchun.song@linux.dev" , "baoquan.he@linux.dev" , "nao.horiguchi@gmail.com" , "matthew.brost@intel.com" , "joshua.hahnjy@gmail.com" , "rakie.kim@sk.com" , "byungchul@sk.com" , "gourry@gourry.net" , "ying.huang@linux.alibaba.com" , "apopple@nvidia.com" , "pfalcato@suse.de" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "damon@lists.linux.dev" , "shakeel.butt@linux.dev" , "ryncsn@gmail.com" , "jparsana@google.com" , "dvander@google.com" , zhangji , wangzicheng References: <20260707063308.29176-1-tao.wangtao@honor.com> <08c001ab-320f-4676-830b-8e4ba6a05dee@kernel.org> <0e8e5a28-1111-4b81-b04f-b81e749eb3dd@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/7/26 11:20, wangtao wrote: >>> I saw it, and I’ve waited for a while as well. >> >> Apparently you saw it but you didn't read my reply about slapping more >> complexity on something complicated. > This v2 is a complete rewrite replacing the original anon_vma and anonymous-page > reverse-mapping traversal. Okay, it leaves the old code in place for now. Just as a general node without going into details: that won't fly. We don't need another MGLRU. > > The new anon_vma hierarchy is represented using a simple doubly linked list with depth information, > replacing the complex topology of red-black trees maintained by each anon_vma in the original design, > and also removing anon_vma_chain. Okay, but anon_vma fundamentally remains. Using a lipstick on a pig. > > Excluding patch 11, which optimizes leaf VMA rmap with PVL, and patch 12, which optimizes memory > usage through shared semaphores, the base version contains roughly 800 lines of code, including the > compatibility part replacing the original anon_vma implementation. > >> >> 12 files changed, 1056 insertions(+), 54 deletions(-) >> >>> >>> If there are technical issues, please point them out directly. >>> Or is this simply how technical discussions are usually conducted in the >> Linux community or the mm subsystem? >> >> I suggest you go back and read my email. > > At first, I thought I was the only one who found anon_vma hard to understand. After reading your earlier email, > I realized that many people also consider it difficult to follow. Right, that's how Lorenzo started his work, trying to replace/remove anon_vma entirely. So I tried a different approach and implemented > anon_vma rmap using a simpler doubly linked list plus depth mechanism. And this is what I don't understand. You were told that Lorenzo is working on removing anon_vma, yet you decided to work on + send something that reworks anon_vma? Also, I am really curious about your expectation: not having a single patch contributed to MM, even worse, not a single RB tag or anything, yet you rework one of the most complicated part of MM repeatedly using other complicated approaches, and immediately start demand technical discussions? After sending an absolute horrible v1? I really try to be a nice person, but really, am I dreaming? Obviously, Lorenzo is still working om his approach, about which there were discussions at conferences and LWN articles. Stating "that you waited for a while" is ludicrous given that your old patch set was posted around one month ago, and a complete redesign -- moving away from anon_vma -- is not expected to be a short-term thing. Meanwhile, Lorenzo is sending real cleanups [1] as preparation for bigger changes. ... which is what we usually expect on such fundamental reworks. I'm really left clueless here why we anyone should spend time trying to thing through yet another data structure and yet another locking scheme, for something we want to remove entirely? Again, I really try to be a nice person, but something here just doesn't add up. [1] https://lore.kernel.org/r/cover.1782735110.git.ljs@kernel.org -- Cheers, David