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Peter Anvin" , Zi Yan , Mike Rapoport , Dave Hansen , Michal Hocko , David Hildenbrand , Lorenzo Stoakes , Andrew Morton , Thomas Gleixner , Nico Pache , Dev Jain , "Liam R . Howlett" , Jens Axboe Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, willy@infradead.org, x86@kernel.org, linux-fsdevel@vger.kernel.org, "Darrick J . Wong" , mcgrof@kernel.org, gost.dev@samsung.com, kernel@pankajraghav.com, hch@lst.de References: <20250527050452.817674-1-p.raghav@samsung.com> <20250527050452.817674-3-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: <20250527050452.817674-3-p.raghav@samsung.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0995918001A X-Stat-Signature: s8dby1isozok1ha83kykug9zaz9mj5kq X-Rspam-User: X-HE-Tag: 1748363875-679223 X-HE-Meta: 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 ktv+Jkbe pHLNvhduIacAP7hfxw7bzstaaKsdOltyQmjY9uXYgsWrKMKCHWIPkQ45BNvhNy2G7s9J/2YUqOIeEEjw96JuMQMJfpFyK1cYgXmj3Z8TvhYZs6zHJlqZest2rJ7IFXsQzMoZCQM1dojnrjSTUK08YsFfXI20SMEXDE0BydEl6u/H9fHx3Zg7p3nw+Tdjmo8w0UB++BHPG7+wCT2AEJHQpVzLPPZbmve6fMX7gf9C+fdkJJHJuO+WtTnV4UlHhN0u4Des5 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 055204dc211d..96f99b4f96ea 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -152,6 +152,7 @@ config X86 > select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64 > select ARCH_WANT_HUGETLB_VMEMMAP_PREINIT if X86_64 > select ARCH_WANTS_THP_SWAP if X86_64 > + select ARCH_WANTS_STATIC_PMD_ZERO_PAGE if X86_64 I don't think this should be the default. There are lots of little x86_64 VMs sitting around and 2MB might be significant to them. > +config ARCH_WANTS_STATIC_PMD_ZERO_PAGE > + bool > + > +config STATIC_PMD_ZERO_PAGE > + def_bool y > + depends on ARCH_WANTS_STATIC_PMD_ZERO_PAGE > + help > + Typically huge_zero_folio, which is a PMD page of zeroes, is allocated > + on demand and deallocated when not in use. This option will always > + allocate huge_zero_folio for zeroing and it is never deallocated. > + Not suitable for memory constrained systems. "Static" seems like a weird term to use for this. I was really expecting to see a 2MB object that gets allocated in .bss or something rather than a dynamically allocated page that's just never freed. > menuconfig TRANSPARENT_HUGEPAGE > bool "Transparent Hugepage Support" > depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT > diff --git a/mm/memory.c b/mm/memory.c > index 11edc4d66e74..ab8c16d04307 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -203,9 +203,17 @@ static void put_huge_zero_page(void) > BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); > } > > +/* > + * If STATIC_PMD_ZERO_PAGE is enabled, @mm can be NULL, i.e, the huge_zero_folio > + * is not associated with any mm_struct. > +*/ I get that callers have to handle failure. But isn't this pretty nasty for mm==NULL callers to be *guaranteed* to fail? They'll generate code for the success case that will never even run.