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[70.52.228.144]) by smtp.gmail.com with ESMTPSA id o5-20020a05620a2a0500b006fc2f74ad12sm22803013qkp.92.2023.01.03.09.09.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Jan 2023 09:09:25 -0800 (PST) Date: Tue, 3 Jan 2023 12:09:23 -0500 From: Peter Xu To: James Houghton Cc: Mike Kravetz , Muchun Song , David Hildenbrand , David Rientjes , Axel Rasmussen , Mina Almasry , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 34/47] hugetlb: userfaultfd: add support for high-granularity UFFDIO_CONTINUE Message-ID: References: <20221021163703.3218176-1-jthoughton@google.com> <20221021163703.3218176-35-jthoughton@google.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 624571C0014 X-Stat-Signature: mnnx94icjg6fd9hcfzkrwwwjzrsidudz X-Rspam-User: X-HE-Tag: 1672765769-959105 X-HE-Meta: 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 RAi41Hav BhKHaJ8/Som04/QS/w57xaScWWYcCzgAlR+OcXCPId04suguyv723HK/QD+pBR9Nm9xDJIsb8RjCIyB540xNm228YsQ2XOAIr3KRfn3u5hu1HRHuK+4bwRbrNlqq9JmgGP7AZqY6jT97wfU2Gbq15K6q/jRLu/raERYUn 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: On Tue, Dec 27, 2022 at 11:38:31AM -0500, James Houghton wrote: > On Fri, Dec 23, 2022 at 1:38 PM Peter Xu wrote: > > > > James, > > > > On Fri, Oct 21, 2022 at 04:36:50PM +0000, James Houghton wrote: > > > + bool use_hgm = uffd_ctx_has_hgm(&dst_vma->vm_userfaultfd_ctx) && > > > + mode == MCOPY_ATOMIC_CONTINUE; > > > > Do you think in your new version use_hgm can work even for MISSING by > > default? > > I don't think so -- UFFDIO_COPY will allocate a hugepage, so I'm not > sure if it makes sense to allow it at high-granularity. If UFFDIO_COPY > didn't allocate a new page, then it could make sense (maybe we'd need > a new ioctl or new UFFDIO_COPY mode?). I think it makes most sense to > add this with another series. I forgot again on how the page cache is managed for the split pages, sorry.. Yeah let's stick with minor mode for now. -- Peter Xu