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 EE44BC43219 for ; Tue, 1 Nov 2022 14:35:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230036AbiKAOfK (ORCPT ); Tue, 1 Nov 2022 10:35:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbiKAOez (ORCPT ); Tue, 1 Nov 2022 10:34:55 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70F1F1BE8F for ; Tue, 1 Nov 2022 07:34:53 -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 1F727336F9; Tue, 1 Nov 2022 14:34:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1667313292; 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=md7UdvagT3X4V8u77OX2NjG4n87gQfkAxPbnmYefNuc=; b=ZFyHqoxeRhYtLuEfJJNaBqeFdVHfTDO5Nw6gJoMHmH7yKnkMiUXJUeYsGswDVHeja9lhMH cixX1+RaowWVAo9iTCEgoLGomWiO4zrBnXZlIsAInL8LqcOmjtZeRrN2OWoBtE0ixgVwPc Qs18LUCGxWBtXDgWEZYyvQkLStW2lYU= 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 CF91F13AAF; 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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