From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.skhynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9DC92261B8D; Tue, 11 Nov 2025 01:41:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762825275; cv=none; b=Ut9a09+Bp+UVRoeShq0LJnmg2834bEEmhiKMo2Q4bA19DhWIwPiJy77To5qfGtYX3FL5Gtz/BWDBY4RXeHLVVs2wzbD0bG+HrxB1p9Hx7moS7XC8njSkrGly87DiQ4ukKs+7HT4B0jGHpEA5O/COvuf1yIrwJ725JxL+rDFYM3I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762825275; c=relaxed/simple; bh=TDgrKCtvuRXiIZq5xR+wrXkse/TzZt+1GBUKp3x1+kg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=drswW5ZoJwP4E3/HeE7Q+3E0wSthC9H3/1Pliiozt93VJx5nQQWfyMyG4S5RL/nQOSpdDIriAaCOeReEj507rlX3L4MsXeVprcQ+XK4BgbyVQhLrtrCPhOjsS7ETaQbJdPSxp3eJMv5ys3uzqmL4/0KoRxvHIm3g3N5KZto8k+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-c45ff70000001609-a1-691294292662 Date: Tue, 11 Nov 2025 10:40:52 +0900 From: Byungchul Park To: Jakub Kicinski Cc: linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel_team@skhynix.com, harry.yoo@oracle.com, ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com, sdf@fomichev.me, saeedm@nvidia.com, leon@kernel.org, tariqt@nvidia.com, mbloch@nvidia.com, andrew+netdev@lunn.ch, edumazet@google.com, pabeni@redhat.com, akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, horms@kernel.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, ilias.apalodimas@linaro.org, willy@infradead.org, brauner@kernel.org, kas@kernel.org, yuzhao@google.com, usamaarif642@gmail.com, baolin.wang@linux.alibaba.com, almasrymina@google.com, toke@redhat.com, asml.silence@gmail.com, bpf@vger.kernel.org, linux-rdma@vger.kernel.org, sfr@canb.auug.org.au, dw@davidwei.uk, ap420073@gmail.com, dtatulea@nvidia.com Subject: Re: [RFC mm v5 1/2] page_pool: check nmdesc->pp to see its usage as page pool for net_iov not page-backed Message-ID: <20251111014052.GA51630@system.software.com> References: <20251103075108.26437-1-byungchul@sk.com> <20251103075108.26437-2-byungchul@sk.com> <20251106173320.2f8e683a@kernel.org> <20251107015902.GA3021@system.software.com> <20251106180810.6b06f71a@kernel.org> <20251107044708.GA54407@system.software.com> <20251107174129.62a3f39c@kernel.org> <20251108022458.GA65163@system.software.com> <20251107183712.36228f2a@kernel.org> <20251110010926.GA70011@system.software.com> Precedence: bulk X-Mailing-List: netdev@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: <20251110010926.GA70011@system.software.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0xTZxjHfc97bjR2eTmT7UXjklWdGU7UhSwPxOu3dx9MlswZs5lsdZxI I1RyQASNWcUalQzGpsZSOoN3bgbTTmgZEIVahCWzQ8DjVKh4YWPchpVYQZHWLPPbL8/l9/w/ PDJWOoX5ssWaq2pWc6ZJNPCGkbmnln94TLGsfBRZAa66WhFqnuXDhZBXgEjtIAeu6noE4cgd CWaaAwie+NtF+KdtAsGZU5MYXDfsPDyte47B1ziIYMhxUYRHgQEJatwbof/8Yx6aDjVgGPjh ugjF9ikMzZFRCQq9lbNij02CYH2JAMeen8PQYAtJcLPRJUJf7YwAj1uLeehwVvEwftyPob9k PQQq3oHJ34YR+OsaOJj8/mcResoaObjc3CPB0a4KER7Y+xF0tQ3wcHz6sAjl+0sQTD2bVY6W hgUov9YnrU9m+3VdZG3DY5j9UnWbY72OH3mmt3RyzOe8J7EK9y7mqUxiRXoXZu7qIyJzT/wk sbu9TSK77pjime9+KvN5n3Cs+MCo+FnCl4bV6WqmJU/VVqz9xpBxuv2wkD2i5L84+BDZ0O23 ipAsU5JCLzWxIhQXw75QgxBlniyhp8vPoiiLZCnV9QiO8jyymNo9ZXwRMsiYjEvUoffFFt4m uXR8zBYbMhKgnuCJGCvEi2l3Dbyux9OOsod8lDFJovrLv7loBkwW0Asv5Wg5jqTSsONQbCSB LKJX6tu56C1KhmUauO8RXwdNpFcrdb4UEecbWucbWuf/2gqEq5FiseZlmS2ZKckZBVZLfvK3 O7PcaPbDzu+b/sqLJoKftyIiI9Nco/5XvEURzHk5BVmtiMrYNM84vY1YFGO6uWCPqu38WtuV qea0ogUyb3rX+PHk7nSFbDfnqjtUNVvV/utyctx8G1rdmfZdtk/7IuXBnJWlC0+yxuDGQfum 2vghznFpyxH+mit8udL9adzmhUMJNwql8B+fDH70InxiU6JNP7jmdyXNWa/t092hFs3Q371j rGXJ+8Eeg2FVWsfa7gkX88/8mnqysHeD3+T98+qy5SOJW5sCtwTXlZD133Xrqkb2vrcl5QMT n5NhXpWEtRzzK8Hu1ERdAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA02Sa0hTcRjG+Z+7w8VxmR3yU+s+MA0KXi0iguggFX1YBFHkqpMudcqmokkw S7FGmprSnKvMSk0n0lY6TbvMtWlX0axjmZqZ3W2ZmUutnBH57cfzPr/n08vgshpyAaPWJAla jSpOTkkIyba1x0JWFMrUYfmPODDXWiioHk+Fin47CV7LWwzMVXUIRr0vaPjd7ELwzemm4GPL CIKLF8ZwMD/OJOB77U8cGhrfIvhgrKHgjWuAhmrrVugrHyKgKbseh4FTrRTkZE7g0OwdpuGo vXJ62KanoeVsGwntdbkkFP68jEO9vp+GzkYzBb2W3yQMOXIIaDNdIcBT5MShL3cDuEqDYOz+ JwTO2noMxk6epaCruBGD681dNJzuKKXgdWYfgo6WAQKKJo9TUJKRi2BifHpyOG+UhJK7vfSG UD5DFCm+5dMXnL92pRvjnxrzCV68eQ/jG0wvab7UmszbKhW8QezAeWvVCYq3jhTQfM/TJopv NU4QfMOrcL7B/g3jc44NU9uDdknWHRDi1CmCNnR9lCSmzH2cTPwsS53KGkR61D3HgPwYjl3N 9fbXkz4m2CVcWckl5GOKXcaJohf3cSC7mMu0FRMGJGFw1kNzRrF3RpjLJnGeL/qZkpQFztZ+ ZoZlrB3nnlTD3zyAayseJHyMswpO/PUeMyBmmoO5il+ML/Zjw7lRY/ZMZR67iLtd58bykNQ0 yzbNsk3/7VKEV6FAtSYlXqWOW7NSFxuTplGnrtyfEG9F009UfmQy345GOzc7EMsgub9UfBeg lpGqFF1avANxDC4PlE7uY9Uy6QFV2mFBm7BXmxwn6BwomCHk86WRO4UoGRutShJiBSFR0P67 YozfAj06/ybAGP3Qu/SIQ1EUaQ3/euhCcXCh4Uf6DVltyC1lkyWddY4/u+NiNAfd6QVZp8Js 63qYjORX0Z5z1X3BO4rEjVNy7wPVrk0hVqsyqOZ6EPHifOdu5fCQ/xblnJJ3ka9zni/Udkft Pm0fWU9ltx2sVCy/6tnjXBQxpYywuNzmo3JCF6NapcC1OtUfc8wNCkADAAA= X-CFilter-Loop: Reflected On Mon, Nov 10, 2025 at 10:09:26AM +0900, Byungchul Park wrote: > On Fri, Nov 07, 2025 at 06:37:12PM -0800, Jakub Kicinski wrote: > > On Sat, 8 Nov 2025 11:24:58 +0900 Byungchul Park wrote: > > > On Fri, Nov 07, 2025 at 05:41:29PM -0800, Jakub Kicinski wrote: > > > > On Fri, 7 Nov 2025 13:47:08 +0900 Byungchul Park wrote: > > > > > The offset of page_type in struct page cannot be used in struct net_iov > > > > > for the same purpose, since the offset in struct net_iov is for storing > > > > > (struct net_iov_area *)owner. > > > > > > > > owner does not have to be at a fixed offset. Can we not move owner > > > > to _pp_mapping_pad ? Or reorder it with type, enum net_iov_type > > > > only has 2 values we can smoosh it with page_type easily. > > > > > > I'm still confused. I think you probably understand what this work is > > > for. (I've explained several times with related links.) Or am I > > > missing something from your questions? > > > > > > I've answered your question directly since you asked, but the point is > > > that, struct net_iov will no longer overlay on struct page. > > > > > > Instead, struct netmem_desc will be responsible for keeping the pp > > > fields while struct page will lay down the resonsibility, once the pp > > > fields will be removed from struct page like: > > > > I understand the end goal. I don't understand why patch 1 is a step > > in that direction, and you seem incapable of explaining it. So please > > either follow my suggestion on how to proceed with patch 2 without > > struct page and struct netmem_desc should keep difference information. > Even though they are sharing some fields at the moment, it should > eventually be decoupled, which I'm working on now. I'm removing the shared space between struct page and struct net_iov so as to make struct page look its own way to be shrinked and let struct net_iov be independent. Introduing a new shared space for page type is non-sense. Still not clear to you? Byungchul > > patch 1 in current form. Or come back when have the full conversion > > ready. > > This patch set represents the final phase of the full conversion process, > awaiting the next steps. Once this patch is completed, the entire > conversion will be finished, allowing for the final patch that removes > the pp fields from the struct page to be carried out. > > Byungchul