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[70.31.26.132]) by smtp.gmail.com with ESMTPSA id y15-20020a05620a0e0f00b006fc2b672950sm2659807qkm.37.2022.12.23.10.38.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Dec 2022 10:38:03 -0800 (PST) Date: Fri, 23 Dec 2022 13:38:02 -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: <20221021163703.3218176-35-jthoughton@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: DEDDD1C000F X-Stat-Signature: 75ahwjxr9yupyonxyxnsbrqxtpas9t36 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1671820686-195231 X-HE-Meta: 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 tVL8pYJ+ 6H+C1UOU7gNx8b+54lPiBVvnGD5ZJxzxwfduzk3DVPZRpEbpkQEb3U/gceYQ25O1GstuM8ykTHpXl0aNNV7OOp/CNKF94l589wn8QTC/5I1dfLCYzZeFuCmk07r9MSO/C/wTqWBoAN/WId8MrZd9JZArT2w== 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: 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 had a feeling that the major components are ready for that anyway. Then no matter how HGM is enabled (assuming it'll switch to MADV, or even one can just register with MISSING+MINOR and enable the uffd HGM feature), an existing MISSING only app can easily switch to HGM support if it's on huge pages. Thanks, -- Peter Xu