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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 57CE1C47DDB for ; Thu, 1 Feb 2024 09:23:02 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rVTGn-0003By-OU; Thu, 01 Feb 2024 04:22:05 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rVTGm-0003A4-A7 for qemu-devel@nongnu.org; Thu, 01 Feb 2024 04:22:04 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rVTGk-0007dE-Fd for qemu-devel@nongnu.org; Thu, 01 Feb 2024 04:22:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706779321; h=from:from:reply-to: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=x8+4xV17TlIOvu9XMgJXRGV7rwdSg/nzPC7T6chB0B0=; b=D9U0vDUDCrsS0UVdT0q8/QkirgqNrVtzfV2vC2uku83z8uXXvKvc0S9/fAxA/8JBRxq47f eRrYBDnSrv9/wr3WjA2nSOPOExvOFF90fGM9Eq2MJRDbW5b31RtmtMW1nODyIDhJP1eYqr dlbHtf/MVWygzkFyJ/CrsNTQTRkAqz8= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-335-g12-6NZBMhCIv597y1zt0w-1; Thu, 01 Feb 2024 04:21:58 -0500 X-MC-Unique: g12-6NZBMhCIv597y1zt0w-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6ABF3868A04; Thu, 1 Feb 2024 09:21:57 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.46]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DFF791BDB1; Thu, 1 Feb 2024 09:21:54 +0000 (UTC) Date: Thu, 1 Feb 2024 09:21:48 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Zhao Liu Cc: Eduardo Habkost , Marcel Apfelbaum , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Yanan Wang , "Michael S . Tsirkin" , Paolo Bonzini , Richard Henderson , Eric Blake , Markus Armbruster , Marcelo Tosatti , qemu-devel@nongnu.org, kvm@vger.kernel.org, Babu Moger , Xiaoyao Li , Zhenyu Wang , Zhuocheng Ding , Yongwei Ma , Zhao Liu Subject: Re: [PATCH v8 00/21] Introduce smp.modules for x86 in QEMU Message-ID: References: <20240131101350.109512-1-zhao1.liu@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.292, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Feb 01, 2024 at 10:57:32AM +0800, Zhao Liu wrote: > Hi Daniel, > > On Wed, Jan 31, 2024 at 10:28:42AM +0000, Daniel P. Berrangé wrote: > > Date: Wed, 31 Jan 2024 10:28:42 +0000 > > From: "Daniel P. Berrangé" > > Subject: Re: [PATCH v8 00/21] Introduce smp.modules for x86 in QEMU > > > > On Wed, Jan 31, 2024 at 06:13:29PM +0800, Zhao Liu wrote: > > > From: Zhao Liu > > [snip] > > > > However, after digging deeper into the description and use cases of > > > cluster in the device tree [3], I realized that the essential > > > difference between clusters and modules is that cluster is an extremely > > > abstract concept: > > > * Cluster supports nesting though currently QEMU doesn't support > > > nested cluster topology. However, modules will not support nesting. > > > * Also due to nesting, there is great flexibility in sharing resources > > > on clusters, rather than narrowing cluster down to sharing L2 (and > > > L3 tags) as the lowest topology level that contains cores. > > > * Flexible nesting of cluster allows it to correspond to any level > > > between the x86 package and core. > > > > > > Based on the above considerations, and in order to eliminate the naming > > > confusion caused by the mapping between general cluster and x86 module > > > in v7, we now formally introduce smp.modules as the new topology level. > > > > What is the Linux kernel calling this topology level on x86 ? > > It will be pretty unfortunate if Linux and QEMU end up with > > different names for the same topology level. > > > > Now Intel's engineers in the Linux kernel are starting to use "module" > to refer to this layer of topology [4] to avoid confusion, where > previously the scheduler developers referred to the share L2 hierarchy > collectively as "cluster". > > Looking at it this way, it makes more sense for QEMU to use the > "module" for x86. I was thinking specificially about what Linux calls this topology when exposing it in sysfs and /proc/cpuinfo. AFAICT, it looks like it is called 'clusters' in this context, and so this is the terminology that applications and users are going to expect. I think it would be a bad idea for QEMU to diverge from this and call it modules. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|