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[2003:cb:c709:6200:16ba:af70:999d:6a1a]) by smtp.gmail.com with ESMTPSA id a8-20020a5d4d48000000b0031c5b380291sm12417507wru.110.2023.08.24.11.33.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 24 Aug 2023 11:33:10 -0700 (PDT) Message-ID: <20e38c1d-24e0-4705-6acb-87921962ccee@redhat.com> Date: Thu, 24 Aug 2023 20:33:09 +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 v1 0/3] udmabuf: Add support for page migration out of movable zone or CMA To: Jason Gunthorpe Cc: "Kasireddy, Vivek" , "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , Daniel Vetter , Mike Kravetz , Hugh Dickins , Peter Xu , Gerd Hoffmann , "Kim, Dongwon" , "Chang, Junxiao" References: <20230817064934.3424431-1-vivek.kasireddy@intel.com> <8afa35bb-c3ed-c939-46a4-a9a277b6d4e2@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-Stat-Signature: 7tbhqgwnw4q3s3zfzre7jxby6mpnskzt X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5679A1C0016 X-HE-Tag: 1692901994-973247 X-HE-Meta: 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 D2mHvhUb 0QwsIWInJRtCK0GOTVzdfc/op8yWauuMFIWIoDIVODOAAOvmVCkRjd8p9KD0MZlh8+9NIyKO4EJzd3HJQsLg4WxhDvvS+GLVAKBWgM1w6gfj+/AdL/kePIUsA0r4XW1f6NIDm5yiALpahZoT35mPYN8ikroeA9FNqpNj7ZlWjh/C/9/bv6cIGW4zxdTF9/nNyy+CXeQAUAbSqnGMRNjSo+P1hKDrCmLV30moMimDsqhR2r97Xc0yJJMX/tygWZlqGtF3DlLc4n2SNx/mjI6BYhsZw0P37W4zRKDbAUDL8Igl3N3UCMp6ee+ZCgzYkjVQz3fOw26b8ATEWoFY3WCx2wYYeryfn1ZuM9N6znUFRX1cxfUH9NBTxWvJsYxg2Jw3SCRnc5BuZXhNjEkeShntH6WdP6y/y1AadAY+aGZLM3kdoKjI= 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 24.08.23 20:30, Jason Gunthorpe wrote: > On Thu, Aug 24, 2023 at 08:30:17PM +0200, David Hildenbrand wrote: >> On 24.08.23 08:31, Kasireddy, Vivek wrote: >>> Hi David, >>> >>>> >>>>>> - Add a new API to the backing store/allocator to longterm-pin the page. >>>>>> For example, something along the lines of >>>> shmem_pin_mapping_page_longterm() >>>>>> for shmem as suggested by Daniel. A similar one needs to be added for >>>>>> hugetlbfs as well. >>>>> >>>>> This may also be reasonable. >>>> >>>> Sounds reasonable to keep the old API (that we unfortunately have) working. >>> I agree; I'd like to avoid adding new APIs unless absolutely necessary. Given this, >>> and considering the options I have mentioned earlier, what would be your >>> recommendation for how page migration needs to be done in udmabuf driver? >> >> I guess using proper APIs for shmem and hugetlb. So, turning roughly what >> you have in patch#1 for now into common code, and only calling into that >> from udmabug. > > This is a lot of work for an obscure uapi :\ Well, what can we otherwise to to *not* break existing users? I'm not happy about this either. Of course, we can come up with a new uapi, but we have to handle the old uapi somehow. Sure, we can simply always fail when we detect ZONE_MOVABLE or MIGRATE_CMA. Maybe that keeps at least some use cases working. -- Cheers, David / dhildenb