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Tue, 1 Nov 2022 14:34:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id TWBUMIsuYWPeRgAAMHmgww (envelope-from ); Tue, 01 Nov 2022 14:34:51 +0000 Date: Tue, 1 Nov 2022 15:34:51 +0100 From: Michal Hocko To: "Huang, Ying" Cc: Bharata B Rao , Aneesh Kumar K V , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Alistair Popple , Dan Williams , Dave Hansen , Davidlohr Bueso , Hesham Almatary , Jagdish Gediya , Johannes Weiner , Jonathan Cameron , Tim Chen , Wei Xu , Yang Shi Subject: Re: [RFC] memory tiering: use small chunk size and more tiers Message-ID: References: <20221027065925.476955-1-ying.huang@intel.com> <578c9b89-10eb-1e23-8868-cdd6685d8d4e@linux.ibm.com> <877d0kk5uf.fsf@yhuang6-desk2.ccr.corp.intel.com> <59291b98-6907-0acf-df11-6d87681027cc@linux.ibm.com> <8735b8jy9k.fsf@yhuang6-desk2.ccr.corp.intel.com> <0d938c9f-c810-b10a-e489-c2b312475c52@amd.com> <87tu3oibyr.fsf@yhuang6-desk2.ccr.corp.intel.com> <07912a0d-eb91-a6ef-2b9d-74593805f29e@amd.com> <87leowepz6.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87leowepz6.fsf@yhuang6-desk2.ccr.corp.intel.com> ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=ZFyHqoxe; spf=pass (imf20.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667313293; a=rsa-sha256; cv=none; b=yGWgCArEJMsJCoAu0hLTrNaxPSeSSfyYQbMRKavKztilBX97pHIwxBA04J3RmZClvQMFJD vRuTJJMqE+H93eegVoH1mZ0gTYrlS0oQl+10oS2f9sDT6XAr6JWC0fcPPkJJGpgC7mNLEE RfeegEHdW+D2IcqyQrArdaNhXAcGglY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667313293; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=md7UdvagT3X4V8u77OX2NjG4n87gQfkAxPbnmYefNuc=; b=8YzYDAi8Nx07gqT5/fxZLQvPiiuGSf/UbmYeKUwLKGyPancYlS2EKDSlXuxWkQXrs83l7F gubFH33d59srz+Xy7B7yrRBblSXO4as4VedXSsx7fu5sogGAj6fTgUI68c4ImY6MICUJEi 2ukCt8JXNwBGDQCIeU8nhS+CaUAwU6o= X-Stat-Signature: oxjpk6cwgddx69jkk15xotgxf6dnnj6p X-Rspamd-Queue-Id: A9A691C0008 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=ZFyHqoxe; spf=pass (imf20.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1667313293-694060 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 Mon 31-10-22 09:33:49, Huang, Ying wrote: [...] > In the upstream implementation, 4 tiers are possible below DRAM. That's > enough for now. But in the long run, it may be better to define more. > 100 possible tiers below DRAM may be too extreme. I am just curious. Is any configurations with more than couple of tiers even manageable? I mean applications have been struggling even with regular NUMA systems for years and vast majority of them is largerly NUMA unaware. How are they going to configure for a more complex system when a) there is no resource access control so whatever you aim for might not be available and b) in which situations there is going to be a demand only for subset of tears (GPU memory?) ? Thanks! -- Michal Hocko SUSE Labs