From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) (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 BD68C1E521C; Thu, 27 Feb 2025 05:20:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740633628; cv=none; b=heZhe1n3m/RNCODh6kdtqpiXodaV5K0Qo4UGnwzU+SUYqXvR8Xcu2SHrCo8Htz0dTu+rCE6BIbChN4I2Y3FUDY/WisWpgPj7o5mxi/fatnbnDwFuYnn8rzWzWBb/r+T3jT3Esik8qPb/nH/rL47b3Z6nVyfpN07yiwmMlvjO6jU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740633628; c=relaxed/simple; bh=vGpcN7P16mx836ZMuMkEdKUR6edRJ0QZzGvP196Ce2I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hhVOtHtdNh4N0eYetHoqHt2sdB3p6KDvz1NVqycsG8umS1zUFJYJVC+li1OHdDi/746GFd/2ot/Qu5koI8p7UHzrhn+Z/JNKGfTSqxCqYGNQehy8vEt5kLow9w9eMOmhq5Lt/cDB3+nwOegCcBuI4Xlw3MGNu8nT2ViLI6Vfv2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=R/E7isyd; arc=none smtp.client-ip=198.175.65.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="R/E7isyd" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1740633626; x=1772169626; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=vGpcN7P16mx836ZMuMkEdKUR6edRJ0QZzGvP196Ce2I=; b=R/E7isydRjOtBFZArtb6+yIu5kNtnnp4JEkcMG10tUR/suBM6UHyhrWj iltXFdv+Jj9sgxcUbFjwapk3cbGbwK/pFgXnbePsxoi3x25t/LSEmJYfb dwJnmN7I6EhpMSef5ZdH5HpRKfX7khFKqvLZY2oyRDkoJVLGQtCyysesx lvUNpQCU5R0yHWQf+HjYNDQR9SMsWrtJCryIdtkfR8RLAqTKWQSPlCuMu +p0fg4jKbYvdWN3usP8aMUStgFbyNZ84LwL1jiP872tEhgUNpXEi0qCSR 7riFWtD13nAAt27ObDj7ta5xorvg6q0QTgY3MATKPXz1N49YH91Jc94aj A==; X-CSE-ConnectionGUID: HDO+E/a3R0mrncXRz1KR7Q== X-CSE-MsgGUID: ejt2W7QEQf+1t4Jpt+BLsw== X-IronPort-AV: E=McAfee;i="6700,10204,11357"; a="41638730" X-IronPort-AV: E=Sophos;i="6.13,319,1732608000"; d="scan'208";a="41638730" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Feb 2025 21:20:26 -0800 X-CSE-ConnectionGUID: Lk/GChz9R1GaGsF8Qphm4A== X-CSE-MsgGUID: M2gLbS9DTJqV6N7Ph1buOQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.13,319,1732608000"; d="scan'208";a="117561459" Received: from allen-sbox.sh.intel.com (HELO [10.239.159.30]) ([10.239.159.30]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Feb 2025 21:20:19 -0800 Message-ID: <35920cb4-05cf-4814-9648-0c7ad39f55aa@linux.intel.com> Date: Thu, 27 Feb 2025 13:17:02 +0800 Precedence: bulk X-Mailing-List: linux-tegra@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 14/23] iommu/pages: Move from struct page to struct ioptdesc and folio To: Jason Gunthorpe Cc: Alim Akhtar , Alyssa Rosenzweig , Albert Ou , asahi@lists.linux.dev, David Woodhouse , Heiko Stuebner , iommu@lists.linux.dev, Jernej Skrabec , Jonathan Hunter , Joerg Roedel , Krzysztof Kozlowski , linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-sunxi@lists.linux.dev, linux-tegra@vger.kernel.org, Marek Szyprowski , Hector Martin , Palmer Dabbelt , Paul Walmsley , Robin Murphy , Samuel Holland , Suravee Suthikulpanit , Sven Peter , Thierry Reding , Tomasz Jeznach , Krishna Reddy , Chen-Yu Tsai , Will Deacon , Bagas Sanjaya , Joerg Roedel , Pasha Tatashin , patches@lists.linux.dev, David Rientjes , Matthew Wilcox References: <14-v3-e797f4dc6918+93057-iommu_pages_jgg@nvidia.com> <20250226135112.GB28425@nvidia.com> Content-Language: en-US From: Baolu Lu In-Reply-To: <20250226135112.GB28425@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/26/25 21:51, Jason Gunthorpe wrote: > On Wed, Feb 26, 2025 at 08:42:23PM +0800, Baolu Lu wrote: >> On 2025/2/26 3:39, Jason Gunthorpe wrote: >>> This brings the iommu page table allocator into the modern world of having >>> its own private page descriptor and not re-using fields from struct page >>> for its own purpose. It follows the basic pattern of struct ptdesc which >>> did this transformation for the CPU page table allocator. >>> >>> Currently iommu-pages is pretty basic so this isn't a huge benefit, >>> however I see a coming need for features that CPU allocator has, like sub >>> PAGE_SIZE allocations, and RCU freeing. This provides the base >>> infrastructure to implement those cleanly. >> I understand that this is intended as the start point of having private >> descriptors for folios allocated to iommu drivers. But I don't believe >> this is currently the case after this patch, as the underlying memory >> remains a struct folio. This patch merely uses an iommu-pages specific >> structure pointer to reference it. > Right now the mm provides 64 bytes of per-page memory that is a struct > page. > > You can call that 64 bytes a struct folio sometimes, and we have now > been also calling those bytes a struct XXdesc like this patch does. > > This is all a slow incremental evolution toward giving each user of > the per-page memory its own unique type and understanding of what it > needs while removing use of of the highly overloaded struct page. > > Eventually Matthew wants to drop the 64 bytes down to 8 bytes and > allocate the per-page memory directly. This would allow each user to > use more/less memory depending on their need. > > https://kernelnewbies.org/MatthewWilcox/Memdescs > > When that happens the > > folio = __folio_alloc_node(gfp | __GFP_ZERO, order, nid); > > Will turn into something maybe more like: > > ioptdesc = memdesc_alloc_node(gfp, order, nid, sizeof(struct ioptdesc)); > > And then the folio word would disappear from this code. > > Right now things are going down Matthew's list: > > https://kernelnewbies.org/MatthewWilcox/Memdescs/Path > > This series is part of "Remove page->lru uses" Cool! Thank you for the explanation. Thanks, baolu