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Wed, 5 Apr 2023 02:00:27 +0000 (GMT) Received: from epsmgms1p1new.samsung.com (unknown [182.195.42.41]) by epsmtrp2.samsung.com (KnoxPortal) with ESMTP id 20230405020027epsmtrp2958bd39a98ddadadcc48e188140e1af7~S52QNBfTV1003310033epsmtrp2-; Wed, 5 Apr 2023 02:00:27 +0000 (GMT) X-AuditID: b6c32a48-9e7f970000008a8d-fe-642cd63ce796 Received: from epsmtip2.samsung.com ( [182.195.34.31]) by epsmgms1p1new.samsung.com (Symantec Messaging Gateway) with SMTP id A6.5A.18071.B36DC246; Wed, 5 Apr 2023 11:00:27 +0900 (KST) Received: from dell-Precision-7920-Tower.dsn.sec.samsung.com (unknown [10.229.83.99]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20230405020027epsmtip2e94be8e8537bddb9e3784a7ab098f603~S52P9gE_w1602716027epsmtip2p; Wed, 5 Apr 2023 02:00:27 +0000 (GMT) From: Kyungsan Kim To: willy@infradead.org Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-cxl@vger.kernel.org, a.manzanares@samsung.com, viacheslav.dubeyko@bytedance.com, dan.j.williams@intel.com, seungjun.ha@samsung.com, wj28.lee@samsung.com Subject: RE: Re: Re: RE(2): FW: [LSF/MM/BPF TOPIC] SMDK inspired MM changes for CXL Date: Wed, 5 Apr 2023 11:00:27 +0900 Message-Id: <20230405020027.413578-1-ks0204.kim@samsung.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrEJsWRmVeSWpSXmKPExsWy7bCmma7NNZ0UgzsveS2mH1a0mD71AqPF +VmnWCz27D3JYnFvzX9Wi32v9zJbvOg8zmTRseENo8XvH3PYLDbef8fmwOXx78QaNo/NK7Q8 Fu95yeSx6dMkdo/JN5YzevRtWcXo8XmTXAB7VLZNRmpiSmqRQmpecn5KZl66rZJ3cLxzvKmZ gaGuoaWFuZJCXmJuqq2Si0+ArltmDtB1SgpliTmlQKGAxOJiJX07m6L80pJUhYz84hJbpdSC lJwC8wK94sTc4tK8dL281BIrQwMDI1OgwoTsjMMXGlgL7vJWrOhdy9TA2M3dxcjJISFgIrF+ 2SO2LkYuDiGBHYwS33/dZQZJCAl8YpTY+c8MIvGNUWLb9E5GmI69fz9DdexllNg7aTUjhNPF JNG34DJYFZuAtsSfK+fZQGwRAXGJY1NPgsWZBf4xSuy5LAliCwuESqy/sIwJxGYRUJVoeHae HcTmFbCROLRyJdQ2eYmZl76DxTmBNh/bMYcRokZQ4uTMJywQM+UlmrfOZgY5QkKglUNi8/+1 LBDNLhK7L0yHGiQs8er4FnYIW0ri87u9bBB2scTj1/+g4iUSh5f8huo1lnh38zlrFyMH0AJN ifW79EFMCQFliSO3oNbySXQc/ssOEeaV6GgTgmhUkdj+bzkzzKLT+zdBDfeQmLDqJwskqNoZ JdbcvMUygVFhFpJvZiH5ZhbC4gWMzKsYxVILinPTU4uNCkzgEZycn7uJEZxYtTx2MM5++0Hv ECMTB+MhRgkOZiURXtUurRQh3pTEyqrUovz4otKc1OJDjKbAsJ7ILCWanA9M7Xkl8YYmlgYm ZmaG5kamBuZK4rwfO5RThATSE0tSs1NTC1KLYPqYODilGpi457Vsbi+5Gr7zHLOmy2QG94km AZeezDqyYyZH12aR0hXHspL6r+/eVPatLCt0StmWMG2dRq0jSU0t8kp/7230jLm8omdtz0aF ZcuubayQiTwS3hXlJeDxba/cD7tH2Z77Q5nPKTHKrJMx/1X076rdSkdlR1mjjXVBTcVpl6dv rNWUD5R/UfZ+1dKoX/Nj/ONn/lwjqfg3yl/y2/v9+o1Kq6y9/k2Jehri75DByefzOurYxXyz Ow+qIqetTLuYW99Y9DKwU+k2c8KfZP4lS398sVXM2hl7dYL81D2WHzmv3BTI1809usNLQfH4 7PbMNHNNtn+3FxefbNW5fXpa4NINCi4FhxdckbJK/Lmt1FaJpTgj0VCLuag4EQDW2LA2NQQA AA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrPLMWRmVeSWpSXmKPExsWy7bCSvK71NZ0Ug61HdSymH1a0mD71AqPF +VmnWCz27D3JYnFvzX9Wi32v9zJbvOg8zmTRseENo8XvH3PYLDbef8fmwOXx78QaNo/NK7Q8 Fu95yeSx6dMkdo/JN5YzevRtWcXo8XmTXAB7FJdNSmpOZllqkb5dAlfG4QsNrAV3eStW9K5l amDs5u5i5OSQEDCR2Pv3M1sXIxeHkMBuRontDRPZIRJSEu9Pt0HZwhL3W46wQhR1MEks/3WG DSTBJqAt8efKeTBbREBc4tjUk4wgRcwgRVsvTwdLCAsES7y7dY8ZxGYRUJVoeHYebCqvgI3E oZUrGSE2yEvMvPQdLM4JdNKxHXPA4kICxhKPjq2HqheUODnzCQuIzQxU37x1NvMERoFZSFKz kKQWMDKtYpRMLSjOTc8tNiwwzEst1ytOzC0uzUvXS87P3cQIjgMtzR2M21d90DvEyMTBeIhR goNZSYRXtUsrRYg3JbGyKrUoP76oNCe1+BCjNAeLkjjvha6T8UIC6YklqdmpqQWpRTBZJg5O qQamSdb9ImfEOrf+2TDr0fYUvWvFTnv3snc8mHW+1npt5w+j86ElDttkr5yXqr9z3tabZcmb QtGiOYx7O8NsNq7xXT3/8cM5Mslvp79f+FWpMk4pzP3zh/usYjlaylLPzwpsTIqf3rgnQY/T f+4U+Vv7p3od3bhr/v3ZD6aUR6ct/ipxJVK7NFB8woHodbo9gVN2cOdLmHex6abdUn3U2iu3 TrymuPaeo/DTlZeCVO/OWpTvdDO6q25RWYDdLPFsx+Y3Mnqr9toKrRETm6Fn/c7544nFVWl/ k71lZjQ8brS7ffSuoN9ePpOLIu/Xuce6+lRfbZW62Bdu9CzplpJ4+jv79Rz3wuOvxKrs/JHz 722VEktxRqKhFnNRcSIAaaqqBfICAAA= X-CMS-MailID: 20230405020027epcas2p4682d43446a493385b60c39a1dbbf07d6 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20230405020027epcas2p4682d43446a493385b60c39a1dbbf07d6 References: X-Rspamd-Queue-Id: 640D44000C X-Stat-Signature: t57gwrdaamwj9rggomo5gjws1u7shwpj X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1680660032-818024 X-HE-Meta: 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 bDd3IZfY J21fJgnHz45J8H3KVW6wbby8ANpe3AgEd2m4uKSrIxG2t20oPxx+jP+JfBiUNiwEQ5TDvSYGa5/VGfesfli5HNT+/M8qRrUvZG7s9XLhGFsh8Fw4= 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 Fri, Mar 31, 2023 at 08:37:15PM +0900, Kyungsan Kim wrote: >> >> We resolved the issue using ZONE_EXMEM by allowing seletively choice of the two usecases. >> > >> >This sounds dangerously confused. Do you want the EXMEM to be removable >> >or not? If you do, then allocations from it have to be movable. If >> >you don't, why go to all this trouble? >> >> I'm sorry to make you confused. We will try more to clearly explain our thought. >> We think the CXL DRAM device should be removable along with HW pluggable nature. >> For MM point of view, we think a page of CXL DRAM can be both movable and unmovable. >> An user or kernel context should be able to determine it. Thus, we think dedication on the ZONE_NORMAL or the ZONE_MOVABLE is not enough. > >No, this is not the right approach. If CXL is to be hot-pluggable, >then all CXL allocations must be movable. If even one allocation on a >device is not movable, then the device cannot be removed. ZONE_EXMEM >feels like a solution in search of a problem We know the situation. When a CXL DRAM channel is located under ZONE_NORMAL, a random allocation of a kernel object by calling kmalloc() siblings makes the entire CXL DRAM unremovable. Also, not all kernel objects can be allocated from ZONE_MOVABLE. ZONE_EXMEM does not confine a movability attribute(movable or unmovable), rather it allows a calling context can decide it. In that aspect, it is the same with ZONE_NORMAL but ZONE_EXMEM works for extended memory device. It does not mean ZONE_EXMEM support both movability and kernel object allocation at the same time. In case multiple CXL DRAM channels are connected, we think a memory consumer possibly dedicate a channel for movable or unmovable purpose.