From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DC395C77B7C for ; Thu, 11 May 2023 15:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238472AbjEKPF6 (ORCPT ); Thu, 11 May 2023 11:05:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237258AbjEKPF5 (ORCPT ); Thu, 11 May 2023 11:05:57 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A921AE7 for ; Thu, 11 May 2023 08:05:55 -0700 (PDT) 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 smtp-out1.suse.de (Postfix) with ESMTPS id 6262721D9A; Thu, 11 May 2023 15:05:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1683817554; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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