From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2a07:de40:b251:101:10:150:64:1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF3D69C; Tue, 5 Dec 2023 00:35:46 -0800 (PST) Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id B5CCD21E40; Tue, 5 Dec 2023 08:35:44 +0000 (UTC) Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id A793E136CF; 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> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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-Spam-Score: 21.50 X-Rspamd-Server: rspamd1 Authentication-Results: smtp-out1.suse.de; dkim=none; spf=fail (smtp-out1.suse.de: domain of mhocko@suse.com does not designate 2a07:de40:b281:104:10:150:64:97 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=suse.com (policy=quarantine) X-Rspamd-Queue-Id: B5CCD21E40 X-Spamd-Result: default: False [21.50 / 50.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_SPF_FAIL(1.00)[-all]; ARC_NA(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_SPAM_SHORT(3.00)[0.999]; MIME_GOOD(-0.10)[text/plain]; MID_RHS_NOT_FQDN(0.50)[]; DMARC_POLICY_QUARANTINE(1.50)[suse.com : No valid SPF, No valid DKIM,quarantine]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_COUNT_THREE(0.00)[3]; MX_GOOD(-0.01)[]; NEURAL_SPAM_LONG(3.50)[1.000]; RCPT_COUNT_TWELVE(0.00)[20]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(2.20)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%] 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