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[2003:cb:c705:d100:871b:ec55:67d:5247]) by smtp.gmail.com with ESMTPSA id 21-20020a05600c025500b003fe1a96845bsm8445619wmj.2.2023.08.01.09.15.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 01 Aug 2023 09:15:50 -0700 (PDT) Message-ID: <30d86a2d-4af2-d840-91be-2e68c73a07bd@redhat.com> Date: Tue, 1 Aug 2023 18:15:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v2 1/8] mm/gup: reintroduce FOLL_NUMA as FOLL_HONOR_NUMA_FAULT To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, Andrew Morton , Linus Torvalds , liubo , Matthew Wilcox , Hugh Dickins , Jason Gunthorpe , John Hubbard , Mel Gorman , Shuah Khan , Paolo Bonzini , stable@vger.kernel.org References: <20230801124844.278698-1-david@redhat.com> <20230801124844.278698-2-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 60B5626D96 X-Stat-Signature: gsck43wihabinj5ut98mi4u39c7w415x X-HE-Tag: 1690906557-87332 X-HE-Meta: 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 sJX/A8Hu JOHWbRYVn/iH4c+yBROgcReR/4SXke0uzdWkKWqstfYcO947xoIKF0In7dWoeBA8woZ02qjBzZ52oRbLcWwQ3ZdYyQ4vKroQz8CLxkJtq3AOCrrfW8nJabbetUIAyE1i97LCozY4LzLUfezFZp6iX5PT3n8KCsFz8e6UTV59kd+kxYCr4K1rDxCwYVWhhteAOyDaFJvQoOiYSWrHFv+NoWyqt3MdlZhVXIFjGRHlujau94LBhfWYf2DYOzCJze6qc2uppK1u+Tg1EqEOMcd2XHGkxr9pnG3wYtqG6WC64Bse2tIKNeMDcOPl9pTixCKqv2RPmuiWIFTXyFdWFIfsd6wGj3ihds0mVKo3D+GFjMor8qGIWcjXD4ZwiH5qtiYO8Lu3DROHAVbQnqm6ulDXAP2L3fbMWN4zATI2c/YAQG8BaQUpcvO1ifJ8OFg== 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 01.08.23 17:48, Peter Xu wrote: > On Tue, Aug 01, 2023 at 02:48:37PM +0200, David Hildenbrand wrote: >> @@ -2240,6 +2244,12 @@ static bool is_valid_gup_args(struct page **pages, int *locked, >> gup_flags |= FOLL_UNLOCKABLE; >> } >> >> + /* >> + * For now, always trigger NUMA hinting faults. Some GUP users like >> + * KVM really require it to benefit from autonuma. >> + */ >> + gup_flags |= FOLL_HONOR_NUMA_FAULT; > > Since at it, do we want to not set it for FOLL_REMOTE, which still sounds > like a good thing to have? I thought about that, but decided against making that patch here more complicated to eventually rip it again all out in #4. I fully agree that FOLL_REMOTE does not make too much sense, but let's rather keep it simple for this patch. Thanks! > > Other than that, looks good here. > > Side note: when I was looking at the flags again just to check the > interactions over numa balancing, I found FOLL_NOFAULT and I highly suspect > that's not needed, instead it just wants to use follow_page[_mask]() with > some proper gup flags passed over.. but that's off topic. Be prepared for my proposal of removing foll_flags from follow_page() ;) (accompanied by a proper documentation) Especially as we have FOLL_PIN users of FOLL_NOFAULT, follow_page() is a bad fit. -- Cheers, David / dhildenb