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(p200300cbc7086100d527e3ca62938440.dip0.t-ipconnect.de. [2003:cb:c708:6100:d527:e3ca:6293:8440]) by smtp.gmail.com with ESMTPSA id l8-20020a5d6688000000b001f04ae0bb6csm4334597wru.58.2022.03.10.07.56.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Mar 2022 07:56:33 -0800 (PST) Message-ID: <30571216-5a6a-7a11-3b2c-77d914025f6d@redhat.com> Date: Thu, 10 Mar 2022 16:56:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.2 Subject: Re: [RFC PATCH 07/14] mm/khugepaged: add vm_flags_ignore to hugepage_vma_revalidate_pmd_count() To: Zach O'Keefe , Alex Shi , David Rientjes , Michal Hocko , Pasha Tatashin , SeongJae Park , Song Liu , Vlastimil Babka , Zi Yan , linux-mm@kvack.org Cc: Andrea Arcangeli , Andrew Morton , Arnd Bergmann , Axel Rasmussen , Chris Kennelly , Chris Zankel , Helge Deller , Hugh Dickins , Ivan Kokshaysky , "James E.J. Bottomley" , Jens Axboe , "Kirill A. Shutemov" , Matthew Wilcox , Matt Turner , Max Filippov , Miaohe Lin , Minchan Kim , Patrick Xia , Pavel Begunkov , Peter Xu , Richard Henderson , Thomas Bogendoerfer , Yang Shi References: <20220308213417.1407042-1-zokeefe@google.com> <20220308213417.1407042-8-zokeefe@google.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220308213417.1407042-8-zokeefe@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 255A41C001E X-Stat-Signature: 5fmwkknihyt5wofarhwfdog958n8osxq X-Rspam-User: Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="PXb/GVYY"; spf=none (imf20.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam07 X-HE-Tag: 1646927796-18198 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 08.03.22 22:34, Zach O'Keefe wrote: > In madvise collapse context, we optionally want to be able to ignore > advice from MADV_NOHUGEPAGE-marked regions. > > Add a vm_flags_ignore argument to hugepage_vma_revalidate_pmd_count() > which can be used to ignore vm flags used when considering thp > eligibility. arch/s390/mm/gmap.c:thp_split_mm() sets VM_NOHUGEPAGE to make sure there are *really* no thp. Being able to bypass that would break KVM horribly. Ignoring MADV_NOHUGEPAGE/VM_NOHUGEPAGE feels like the wrong way to go. What about a prctl instead, to disable any khugepagd activity and just let that process control it manually? -- Thanks, David / dhildenb