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Tue, 5 Dec 2023 08:35:44 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 8JPnKODgbmWjPAAAD6G6ig (envelope-from ); Tue, 05 Dec 2023 08:35:44 +0000 Date: Tue, 5 Dec 2023 09:35:44 +0100 From: Michal Hocko To: Srinivasulu Thanneeru Cc: aneesh.kumar@linux.ibm.com, linux-cxl@vger.kernel.org, linux-mm@kvack.org, dan.j.williams@intel.com, hannes@cmpxchg.org, hasanalmaruf@fb.com, haowang3@fb.com, ying.huang@intel.com, gregory.price@memverge.com, tj@kernel.org, hezhongkun.hzk@bytedance.com, fvdl@google.com, john@jagalactic.com, emirakhur@micron.com, vtavarespetr@micron.com, Ravis.OpenSrc@micron.com, Jonathan.Cameron@huawei.com, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [EXT] Re: [RFC PATCH 0/2] Node migration between memory tiers Message-ID: References: <20231130220422.2033-1-sthanneeru.opensrc@micron.com> <1db561a9-6984-418d-9305-a2a5ece93696@micron.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1db561a9-6984-418d-9305-a2a5ece93696@micron.com> X-Spamd-Bar: +++++++++++++++++++++ X-Stat-Signature: n7u3iies5xt5dgco46zf78krf9asosj7 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 8F7212000C X-Rspam-User: X-HE-Tag: 1701765346-215947 X-HE-Meta: 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 J1TM9ZVX nY3ifZDFWODhsA6PdNLjdNjHzb4iaVaNgBCgQ83l87C0laMWzIhaniwzPfGaVnDhMaNmyDFeO++SUe3d1EyMRWKk3MR18Du8uZD39mCQyt+w62VSV0+OuOXcW+eo/2CeQQZZNL9NkLT6fYHfPiNVuuvwOj/gQq8W1Hj4e51GV/LFfoxL6pzfTEhZ+ixakQP5DAY81przycSMg2Cw= 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: List-Subscribe: List-Unsubscribe: On Tue 05-12-23 01:26:07, Srinivasulu Thanneeru wrote: > > > On 12/4/2023 9:13 PM, Michal Hocko wrote: > > CAUTION: EXTERNAL EMAIL. Do not click links or open attachments unless you recognize the sender and were expecting this message. > > > > > > On Fri 01-12-23 03:34:20, sthanneeru.opensrc@micron.com wrote: > > > From: Srinivasulu Thanneeru > > > > > > The memory tiers feature allows nodes with similar memory types > > > or performance characteristics to be grouped together in a > > > memory tier. However, there is currently no provision for > > > moving a node from one tier to another on demand. > > > > Could you expand on why this is really needed/necessary? What is the > > actual usecase? > > Hi Michal Hock, > > Following two use-cases we have observed. > 1. It is not accurate to group similar memory types in the same tier, > because even similar memory types may have different speed grades. Presumably they are grouped based on a HW configuration. Does that mean that the configuration is wrong? Are you trying to workaround that by this interface? > 2. Some systems boots up with CXL devices and DRAM on the same memory-tier, > we need a way to move the CXL nodes to the correct tier from the user space. Again, could you expand a bit more and explain why this cannot be configured automatically? -- Michal Hocko SUSE Labs