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Wed, 2 Nov 2022 07:51:38 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Z+cmF4ohYmPjdAAAMHmgww (envelope-from ); Wed, 02 Nov 2022 07:51:38 +0000 Date: Wed, 2 Nov 2022 08:51:37 +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: <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> <878rkuchpm.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <878rkuchpm.fsf@yhuang6-desk2.ccr.corp.intel.com> ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1667375500; 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=D7DuwjAkYM/Dv14i5yvJmY3bptRAmV3B0bXlSokhvkU=; b=zzb5mKdCY5goqx95U6KeK6bW3vRQoMwhZCyMbBiLvQzKHRKdodsNOO6kSEjpal8aE+7tLB KJn7qQ4LSEjo2k8gURbm5SOuQdrTuPzz/nPZurR9dn4jX7FbMs3M2pUxgcduUoyCq1aeuL qyjtjJVXWdx2T7NtjhUyOevl2cGQMP0= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=p9XCoIBR; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf09.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667375500; a=rsa-sha256; cv=none; b=7f/zAGKAB9Bw2iN2qfvbQxTzV4NpM0AS9+E0r8UNtKVUmxsycJn+W50U+OvCVcBpCVdVLV Kg3f6AOPz3Kb1ZJkVxWSd7razWjo4j8GoATu27dSwEySiwbFIe0PxGk072Eg/oH2zWOKl4 SvSISQaKjhwbmi6RZNRJssfM+I10o+w= Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=p9XCoIBR; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf09.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: E6004140002 X-Stat-Signature: takazjzuk8fcaxu7rui6h8iu3ng7gdwf X-HE-Tag: 1667375499-811088 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 Wed 02-11-22 08:39:49, Huang, Ying wrote: > Michal Hocko writes: > > > 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?) ? > > Sorry for confusing. I think that there are only several (less than 10) > tiers in a system in practice. Yes, here, I suggested to define 100 (10 > in the later text) POSSIBLE tiers below DRAM. My intention isn't to > manage a system with tens memory tiers. Instead, my intention is to > avoid to put 2 memory types into one memory tier by accident via make > the abstract distance range of each memory tier as small as possible. > More possible memory tiers, smaller abstract distance range of each > memory tier. TBH I do not really understand how tweaking ranges helps anything. IIUC drivers are free to assign any abstract distance so they will clash without any higher level coordination. -- Michal Hocko SUSE Labs