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b=r48m1IfzWwY8XNCkaYv/YCKAzJM+/FW/Rc30nfLBjG41id+q0Ji5+B+7rPEuNny/L Af+ISgcAfGDTY7Ot41P/wWo68nqBI+OoI8wk0qDZpI3+9XT2pQzxS3XwAMAb+KK9r8 xOBIi1xHAo+NFXQ98VYnjZMD7wbeMNy9kDEDzz3o= Date: Thu, 15 Aug 2024 15:35:24 -0700 From: Andrew Morton To: Huan Yang Cc: usamaarif642@gmail.com, yuzhao@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, opensource.kernel@vivo.com Subject: Re: [PATCH] mm: move the easily assessable conditions forward Message-Id: <20240815153524.6bb7c26dc32feb93dd1ba513@linux-foundation.org> In-Reply-To: <20240815083102.653820-1-link@vivo.com> References: <20240815083102.653820-1-link@vivo.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: je7mr14hc415adp4soornyj8184bmu7m X-Rspam-User: X-Rspamd-Queue-Id: 3AE31A001F X-Rspamd-Server: rspam02 X-HE-Tag: 1723761329-199455 X-HE-Meta: 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 VJE9x/b7 VSKnEoBQzkMaJiE3dPL2+kcGWS1R78biR/VlBHeqhwhyeu0+zY/wG175iycIwTbFX0oa0AdRoDhwkh7GuJfk64qYYPIJ8RLne3c8dKQit3OFbOyXz8KJyTSFvwAKNWpX88OzA+48ccPMmlzUYWICakS9kQYot3l4U63qHcw4ty/u387eznZ/ccUpE3wKHHJPDtzZ0eptvkhrkxZxMLYsoMc+gtO1xOm6XjtIXV8QwGBC0l92RPRF5vUWbbDmzkBSxzj0HARcDQMp4/Q7fOoo2V4kWtQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 15 Aug 2024 16:31:01 +0800 Huan Yang wrote: > Current try_to_map_unused_to_zeropage try to use shared zero page to > save some memory of sub page. > > If forbids zeropage, no need to do anything rather than attempting to > assess wthether to use it afterwards. > > ... > > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -192,6 +192,9 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, > VM_BUG_ON_PAGE(!PageLocked(page), page); > VM_BUG_ON_PAGE(pte_present(*pvmw->pte), page); > > + if (mm_forbids_zeropage(pvmw->vma->vm_mm)) > + return false; > + > if (PageMlocked(page) || (pvmw->vma->vm_flags & VM_LOCKED)) > return false; > > @@ -204,7 +207,7 @@ static bool try_to_map_unused_to_zeropage(struct page_vma_mapped_walk *pvmw, > contains_data = memchr_inv(addr, 0, PAGE_SIZE); > kunmap_local(addr); > > - if (contains_data || mm_forbids_zeropage(pvmw->vma->vm_mm)) > + if (contains_data) > return false; > Looks sensible. I'll add it as a fixup to "mm: remap unused subpages to shared zeropage when splitting isolated thp".