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 X-Spam-Level: X-Spam-Status: No, score=-4.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E72D8C4363C for ; Wed, 7 Oct 2020 05:15:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E9F720B1F for ; Wed, 7 Oct 2020 05:15:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602047752; bh=ANfQhwGzorCY3vkKqVqlFWIvj91DN6/XmR+ZZcnxwk8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=h75OUtU8YOd5r9sbKU8bWwNdfTCgRGoM3ZZDj6+faSth7d7r1PphMXAJxUbdV2No4 DcUmKuXVlq/LH/ruj/snDHp8uE1dgCyfFBT8Tl6t5iy4LRTH+zw9eWK3Nzt7i4nQ3b r6hSLXps0bzXjNhqfQOVQGcUpQKBnm+idRpQTc8k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726438AbgJGFPv (ORCPT ); Wed, 7 Oct 2020 01:15:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:35898 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726041AbgJGFPv (ORCPT ); Wed, 7 Oct 2020 01:15:51 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 67CA7208C7; Wed, 7 Oct 2020 05:15:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602047749; bh=ANfQhwGzorCY3vkKqVqlFWIvj91DN6/XmR+ZZcnxwk8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1qpIDSwyz6Byq1l6YiRmkSwSfodaPH0tuefE5CjJZ6NQRypdptyq2UgLkSNjuT2U0 /AMiRKv1VzqZ900W80iWTv5Oc9Ta2HzFqVoyfgCpgYFiaTztmXaOcHDZ8J2WbS1VXX 3SABi8Isr4ueVZy0NME1WLfxRFdZ7t1kQEwxZSF8= Date: Wed, 7 Oct 2020 07:15:46 +0200 From: Greg Kroah-Hartman To: Ricardo Neri Cc: x86@kernel.org, Borislav Petkov , Ingo Molnar , Thomas Gleixner , "Rafael J. Wysocki" , Tony Luck , Len Brown , "Ravi V. Shankar" , linux-kernel@vger.kernel.org, Andi Kleen , Dave Hansen , "Gautham R. Shenoy" , Kan Liang , Srinivas Pandruvada Subject: Re: [PATCH 1/4] drivers core: Introduce CPU type sysfs interface Message-ID: <20201007051546.GA47583@kroah.com> References: <20201003011745.7768-1-ricardo.neri-calderon@linux.intel.com> <20201003011745.7768-2-ricardo.neri-calderon@linux.intel.com> <20201003085345.GA114893@kroah.com> <20201006005736.GD6041@ranerica-svr.sc.intel.com> <20201006073744.GA6753@kroah.com> <20201007031447.GB27938@ranerica-svr.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201007031447.GB27938@ranerica-svr.sc.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 06, 2020 at 08:14:47PM -0700, Ricardo Neri wrote: > On Tue, Oct 06, 2020 at 09:37:44AM +0200, Greg Kroah-Hartman wrote: > > On Mon, Oct 05, 2020 at 05:57:36PM -0700, Ricardo Neri wrote: > > > On Sat, Oct 03, 2020 at 10:53:45AM +0200, Greg Kroah-Hartman wrote: > > > > On Fri, Oct 02, 2020 at 06:17:42PM -0700, Ricardo Neri wrote: > > > > > Hybrid CPU topologies combine CPUs of different microarchitectures in the > > > > > same die. Thus, even though the instruction set is compatible among all > > > > > CPUs, there may still be differences in features (e.g., some CPUs may > > > > > have counters that others CPU do not). There may be applications > > > > > interested in knowing the type of micro-architecture topology of the > > > > > system to make decisions about process affinity. > > > > > > > > > > While the existing sysfs for capacity (/sys/devices/system/cpu/cpuX/ > > > > > cpu_capacity) may be used to infer the types of micro-architecture of the > > > > > CPUs in the platform, it may not be entirely accurate. For instance, two > > > > > subsets of CPUs with different types of micro-architecture may have the > > > > > same capacity due to power or thermal constraints. > > > > > > > > > > Create the new directory /sys/devices/system/cpu/types. Under such > > > > > directory, create individual subdirectories for each type of CPU micro- > > > > > architecture. Each subdirectory will have cpulist and cpumap files. This > > > > > makes it convenient for user space to read all the CPUs of the same type > > > > > at once without having to inspect each CPU individually. > > > > > > > > > > Implement a generic interface using weak functions that architectures can > > > > > override to indicate a) support for CPU types, b) the CPU type number, and > > > > > c) a string to identify the CPU vendor and type. > > > > > > > > > > For example, an x86 system with one Intel Core and four Intel Atom CPUs > > > > > would look like this (other architectures have the hooks to use whatever > > > > > directory naming convention below "types" that meets their needs): > > > > > > > > > > user@host:~$: ls /sys/devices/system/cpu/types > > > > > intel_atom_0 intel_core_0 > > > > > > > > > > user@host:~$ ls /sys/devices/system/cpu/types/intel_atom_0 > > > > > cpulist cpumap > > > > > > > > > > user@host:~$ ls /sys/devices/system/cpu/types/intel_core_0 > > > > > cpulist cpumap > > > > > > > > > > user@host:~$ cat /sys/devices/system/cpu/types/intel_atom_0/cpumap > > > > > 0f > > > > > > > > > > user@host:~$ cat /sys/devices/system/cpu/types/intel_atom_0/cpulist > > > > > 0-3 > > > > > > > > > > user@ihost:~$ cat /sys/devices/system/cpu/types/intel_core_0/cpumap > > > > > 10 > > > > > > > > > > user@host:~$ cat /sys/devices/system/cpu/types/intel_core_0/cpulist > > > > > 4 > > > > > > Thank you for the quick and detailed Greg! > > > > > > > > > > > The output of 'tree' sometimes makes it easier to see here, or: > > > > grep -R . * > > > > also works well. > > > > > > Indeed, this would definitely make it more readable. > > > > > > > > > > > > On non-hybrid systems, the /sys/devices/system/cpu/types directory is not > > > > > created. Add a hook for this purpose. > > > > > > > > Why should these not show up if the system is not "hybrid"? > > > > > > My thinking was that on a non-hybrid system, it does not make sense to > > > create this interface, as all the CPUs will be of the same type. > > > > Why not just have this an attribute type in the existing cpuX directory? > > Why do this have to be a totally separate directory and userspace has to > > figure out to look in two different spots for the same cpu to determine > > what it is? > > But if the type is located under cpuX, usespace would need to traverse > all the CPUs and create its own cpu masks. Under the types directory it > would only need to look once for each type of CPU, IMHO. What does a "mask" do? What does userspace care about this? You would have to create it by traversing the directories you are creating anyway, so it's not much different, right? > > That feels wasteful, it should be much simpler to use the existing > > object, right? > > > > That way, you also show the "type" of all cpus, no matter if they are > > "hybrid" or not, again, making userspace deal with things in a much > > simpler manner. > > Indeed, that would be simpler to implement, and perhaps a natural extension > of the existing interface. > > Lastly, legacy and non-hybrid parts will not have a type defined. Thus, > it may not make sense for them to expose a type in sysfs. That's fine, not having a sysfs file if you don't know the type is fine. Or you can fix that up and show the type of those as well, why wouldn't you want to? > > > I thought of this as maybe intel_atcm vs a potential amd_minizen. I > > > guess arch is sufficient, as there will never be an amd_atom. > > > > Even if there is, that can be part of the cpu "type" that you have for > > your enumerated type, right? > > Indeed. The interface I propose lets archs define their own string > names. Arches _should_ define their own names, otherwise who would? thanks, greg k-h