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X-IronPort-AV: E=McAfee;i="6600,9927,10707"; a="331055132" X-IronPort-AV: E=Sophos;i="5.99,269,1677571200"; d="scan'208";a="331055132" Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 May 2023 20:09:39 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10707"; a="824209974" X-IronPort-AV: E=Sophos;i="5.99,269,1677571200"; d="scan'208";a="824209974" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.238.208.55]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 May 2023 20:09:35 -0700 From: "Huang, Ying" To: Dave Hansen Cc: , , Arjan Van De Ven , Andrew Morton , Mel Gorman , Vlastimil Babka , "David Hildenbrand" , Johannes Weiner , "Dave Hansen" , Michal Hocko , "Pavel Tatashin" , Matthew Wilcox Subject: Re: [RFC 0/6] mm: improve page allocator scalability via splitting zones References: <20230511065607.37407-1-ying.huang@intel.com> Date: Fri, 12 May 2023 11:08:32 +0800 In-Reply-To: (Dave Hansen's message of "Thu, 11 May 2023 07:23:51 -0700") Message-ID: <87mt2a8cwf.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: C6BCCC0005 X-Stat-Signature: eawuh38y7h9pperd9e7cccs8sr6bc3ob X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1683860980-865418 X-HE-Meta: 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 TKDh4Yz/ 4jbg41tE8ljIoS2IgBnSnCpEqqdaQb6m+uU7GMTnot+vVRLntpmVoTHJRSczgGTI52pryp3ASSPyvmhuxugWEeQHrh0GHmheJmXym/7j1mf2IzwFMJ19iYoS3dRl0C+Xe6BT4nAFAZ+7QeFmNqiphPNL94z/EbNGCyd+Ef+q34tk7nak= 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: Hi, Dave, Dave Hansen writes: > On 5/10/23 23:56, Huang Ying wrote: >> To improve the scalability of the page allocation, in this series, we >> will create one zone instance for each about 256 GB memory of a zone >> type generally. That is, one large zone type will be split into >> multiple zone instances. > > A few anecdotes for why I think _some_ people will like this: > > Some Intel hardware has a "RAM" caching mechanism. It either caches > DRAM in High-Bandwidth Memory or Persistent Memory in DRAM. This cache > is direct-mapped and can have lots of collisions. One way to prevent > collisions is to chop up the physical memory into cache-sized zones and > let users choose to allocate from one zone. That fixes the conflicts. > > Some other Intel hardware a ways to chop a NUMA node representing a > single socket into slices. Usually one slice gets a memory controller > and its closest cores. Intel calls these approaches Cluster on Die or > Sub-NUMA Clustering and users can select it from the BIOS. > > In both of these cases, users have reported scalability improvements. > We've gone as far as to suggest the socket-splitting options to folks > today who are hitting zone scalability issues on that hardware. > > That said, those _same_ users sometimes come back and say something > along the lines of: "So... we've got this app that allocates a big hunk > of memory. It's going slower than before." They're filling up one of > the chopped-up zones, hitting _some_ kind of undesirable reclaim > behavior and they want their humpty-dumpty zones put back together again > ... without hurting scalability. Some people will never be happy. :) Thanks a lot for your valuable input! > Anyway, _if_ you do this, you might also consider being able to > dynamically adjust a CPU's zonelists somehow. That would relieve > pressure on one zone for those uneven allocations. That wasn't an > option in the two cases above because users had ulterior motives for > sticking inside a single zone. But, in your case, the zones really do > have equivalent performance. Yes. For the requirements you mentioned above, we need a mechanism to adjust a CPU's zonelists dynamically. I will not implement that in this series. But I think that it's doable based on the multiple zone instances per zone type implementation in this series. Best Regards, Huang, Ying