From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.7]) (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 58BDD248F6F; Thu, 12 Jun 2025 14:09:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749737378; cv=none; b=mhHdwozdNnklyT21j7fsB+xdzdoYVayboz5mOZfAG1PCaO75C1xMltZ8wNhXD25unNkFYcVxmaRXiOWTK8Mi+7KmMwmNdlYsiDtIOUqh7CJqClwTR+rXw7haZH2V0Z5MhB1N20PWDp1wjcBVqz86NtAL1sq6Ympj47y03RSzyuM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749737378; c=relaxed/simple; bh=kdkVV2FGMOSgAFU+V5temNkk1TA2PJJ7nYDpbTdZuw0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rUxdon4K9at5tkX1A38Pw5Y/ucyRvOpO+UwsHDCc9qwN231OVIopYJgBbn5zPcB0o4nOuMPOPHzFNkP56w+9rzrwHvsY1saGIzbQcuq/Pp0onR0MaBil2axZA4CgUNJMmfPr7rlofxPUxtdYfsI6dHnyp0eomW4rFeMb7oikEyc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=NHEAoLKC; arc=none smtp.client-ip=192.198.163.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="NHEAoLKC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1749737377; x=1781273377; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=kdkVV2FGMOSgAFU+V5temNkk1TA2PJJ7nYDpbTdZuw0=; b=NHEAoLKCY9eMbMvyrktQa8LtOyOKRk3cTGfMPIEQVsCOGHkpGbvz/AFF 0+K7PNi5EfrojbqPuUM3ERhTiZ6Zyeg/LGYJi860qyepFv8SGTHGyfDqk VKIIT8Z7jiMLjCcZ5H2aPgYwz/HKEK4bf4YVSi4ePlYPD1QsaDAPFwjmK VNwx0Z7uaYg76az624aJNkD4oNVDtCxGfYgS6TqHzjy6v7LswAtsX79W4 WVLw30UwrvhS2sLyRXROXOKKe5wNx3IkX0GBcA74DHCFFzDIVFghkGLFm EyN7/Spb0t7PXMlTZUMD+Ny/FlPp4URjnjz+2Nv+RAmyUleWoqqDdoKYj g==; X-CSE-ConnectionGUID: sbxAvL3LQxSUW1rVkvb5kA== X-CSE-MsgGUID: T09uEs14R3Cywqb4Zkpe3g== X-IronPort-AV: E=McAfee;i="6800,10657,11462"; a="77323439" X-IronPort-AV: E=Sophos;i="6.16,231,1744095600"; d="scan'208";a="77323439" Received: from orviesa007.jf.intel.com ([10.64.159.147]) by fmvoesa101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jun 2025 07:09:35 -0700 X-CSE-ConnectionGUID: uXkU0nvlR9yZhAhwkLy+EA== X-CSE-MsgGUID: b77Tdni3R3i8puDUUZrwVQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,231,1744095600"; d="scan'208";a="148086031" Received: from kcaccard-desk.amr.corp.intel.com (HELO [10.125.111.188]) ([10.125.111.188]) by orviesa007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Jun 2025 07:09:35 -0700 Message-ID: Date: Thu, 12 Jun 2025 07:09:34 -0700 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/5] mm: add mm_get_static_huge_zero_folio() routine To: Pankaj Raghav , Suren Baghdasaryan , Ryan Roberts , Mike Rapoport , Michal Hocko , Thomas Gleixner , Nico Pache , Dev Jain , Baolin Wang , Borislav Petkov , Ingo Molnar , "H . Peter Anvin" , Vlastimil Babka , Zi Yan , Dave Hansen , David Hildenbrand , Lorenzo Stoakes , Andrew Morton , "Liam R . Howlett" , Jens Axboe Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, willy@infradead.org, x86@kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Darrick J . Wong" , mcgrof@kernel.org, gost.dev@samsung.com, kernel@pankajraghav.com, hch@lst.de References: <20250612105100.59144-1-p.raghav@samsung.com> <20250612105100.59144-5-p.raghav@samsung.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: <20250612105100.59144-5-p.raghav@samsung.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/12/25 03:50, Pankaj Raghav wrote: > +/* > + * mm_get_static_huge_zero_folio - Get a PMD sized zero folio Isn't that a rather inaccurate function name and comment? The third line of the function literally returns a non-PMD-sized zero folio. > + * This function will return a PMD sized zero folio if CONFIG_STATIC_PMD_ZERO_PAGE > + * is enabled. Otherwise, a ZERO_PAGE folio is returned. > + * > + * Deduce the size of the folio with folio_size instead of assuming the > + * folio size. > + */ > +static inline struct folio *mm_get_static_huge_zero_folio(void) > +{ > + if(IS_ENABLED(CONFIG_STATIC_PMD_ZERO_PAGE)) > + return READ_ONCE(huge_zero_folio); > + return page_folio(ZERO_PAGE(0)); > +} This doesn't tell us very much about when I should use: mm_get_static_huge_zero_folio() vs. mm_get_huge_zero_folio(mm) vs. page_folio(ZERO_PAGE(0)) What's with the "mm_" in the name? Usually "mm" means "mm_struct" not Memory Management. It's really weird to prefix something that doesn't take an "mm_struct" with "mm_" Isn't the "get_" also a bad idea since mm_get_huge_zero_folio() does its own refcounting but this interface does not? Shouldn't this be something more along the lines of: /* * pick_zero_folio() - Pick and return the largest available zero folio * * mm_get_huge_zero_folio() is preferred over this function. It is more * flexible and can provide a larger zero page under wider * circumstances. * * Only use this when there is no mm available. * * ... then other comments */ static inline struct folio *pick_zero_folio(void) { if (IS_ENABLED(CONFIG_STATIC_PMD_ZERO_PAGE)) return READ_ONCE(huge_zero_folio); return page_folio(ZERO_PAGE(0)); } Or, maybe even name it _just_: zero_folio()