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bh=dNWze48V6JBTc+Hd2zEHP1xFisIRIn+nKrZWWVUxuYM=; b=NMFmJVzuyE7uLEcxwRMv3NkqS9gNs9ykrysnIVK4bhceKDV91FcmSKnbOeGbrf9TXgGdj0 85Bk+it2j38zsoMIe737vRUpWWCBnYACF7ZyBpd1r4oNPQ+ws4xCylYRTg1k+WMr5iKz9C FAVPL0UH2gOpsV7bTfEQ4yiC4UzCD4E= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id DF164138FA; Thu, 11 May 2023 15:05:53 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id YZX4KVEEXWRIYQAAMHmgww (envelope-from ); Thu, 11 May 2023 15:05:53 +0000 Date: Thu, 11 May 2023 17:05:51 +0200 From: Michal Hocko To: Huang Ying Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Arjan Van De Ven , Andrew Morton , Mel Gorman , Vlastimil Babka , David Hildenbrand , Johannes Weiner , Dave Hansen , Pavel Tatashin , Matthew Wilcox Subject: Re: [RFC 0/6] mm: improve page allocator scalability via splitting zones Message-ID: References: <20230511065607.37407-1-ying.huang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230511065607.37407-1-ying.huang@intel.com> X-Stat-Signature: 8b1c1ec7t4o4qmej7jnaqjwfgfqbj8ho X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E61AB4089C X-Rspam-User: X-HE-Tag: 1683817555-24132 X-HE-Meta: U2FsdGVkX187fbFfeLrEdHzCxCc4wTyP4kS5w5IhkbuPb+X18jnCrs/JaHyv1d/YEFFWSNn4AQ0XWsqzbHIi3KwCUGeP9+FC1e9flnD/KI/bQNryjTlRRsd2R6zdE66pqJZrtHJpCsdVfNXTbUOiygQOuFbrg1foCekStbfD1D/SMEHCTlsNipR8Juq7AZMD7QsKMnnrUXqVGTPDLZkap12iwwNclXqzGCV2QllAPl5SpOsiEPbNw9CoS1HJ9yNRkg2Orjlvko2+ig1vm8p9wGMjtQdyuEu5laYYa54v8oDktMq+E2XY+K10oWaeDFla3owhUgDD4qOHTZeF511tTXeZgsQUApIHHoKE8IE44Bk0j+NuykCOFregn3CjDE11Uf0NjBxUZsOuaKyDk/Vt12eQ9kJbp80DPEs/NKFHd/3DFJgn/EMUZje4QSrcPL/t/+NhfmqkIIIwO1ugw5OnjgH+69eKfUsorGtNvpjAoXG/5Qx2kjx/m3py/v0TvjN5dTJUCHPjWG884TCJVQDPk84LVp1hM2PJ/YtBYxLgEaCKI+M5DvCn3HRmW9/mdPT30/UjRlYoXCLSOkO62XvpghToYYz1dJzkoXGGvO4oqZA1mziWkTXm18yHv7LAaKH0Nnrgpkk2YawEYp80V8exneGY5FypyMWCEF5ng56Zm7xSuNPfAjok/WmGDPs+VIYgarvS840Cj4ZF0oKj47aCbUDr/uQ/ypLqR/gWYrEQAWnnaT8puuWHXbryZz2M4rugOCbXOtYLeZuqRCwpi3AD7K7DTEY98eMhduEOvT57ii3gbYrNzRKblmdZ+bsUlXNy/wSNFC8iqf8PswU9ymxfvMlHfpsRKluOvtBow0NNxBP1aLizhgLlrn8UtEY48bZf9jtiK/ZKKsfUFSYdtxD8/g2xjIn+LFrivQza6dfrJKBUAA0ZC13ix6akhNSyn8F/Kc5HkcY2ZmiERfAVwWl kbcbQ6MC jDOa9PFClTjpUGnT2mn9EGJb7rVLO2AF8vU3Z7BoytzJ2zvNGCfAb51BamCKrUMKlDIh8KysS0YaSfw8rtZ+dR0uYfvabIfJJHjs/k/Wi7rg8eKN85WWKqUtMxIvkfxcKMDqbLZ46PeBqdbvNcxV+PizY7Q== 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 Thu 11-05-23 14:56:01, Huang Ying wrote: > The patchset is based on upstream v6.3. > > More and more cores are put in one physical CPU (usually one NUMA node > too). In 2023, one high-end server CPU has 56, 64, or more cores. > Even more cores per physical CPU are planned for future CPUs. While > all cores in one physical CPU will contend for the page allocation on > one zone in most cases. This causes heavy zone lock contention in > some workloads. And the situation will become worse and worse in the > future. > > For example, on an 2-socket Intel server machine with 224 logical > CPUs, if the kernel is built with `make -j224`, the zone lock > contention cycles% can reach up to about 12.7%. > > 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. Then, different logical CPUs will prefer > different zone instances based on the logical CPU No. So the total > number of logical CPUs contend on one zone will be reduced. Thus the > scalability is improved. It is not really clear to me why you need a new zone for all this rather than partition free lists internally within the zone? Essentially to increase the current two level system to 3: per cpu caches, per cpu arenas and global fallback. I am also missing some information why pcp caches tunning is not sufficient. -- Michal Hocko SUSE Labs