From mboxrd@z Thu Jan 1 00:00:00 1970 From: sudeep.holla@arm.com (Sudeep Holla) Date: Tue, 6 Nov 2018 14:13:49 +0000 Subject: [RFC 0/2] Add RISC-V cpu topology In-Reply-To: <866dedbc78ab4fa0e3b040697e112106@mailhost.ics.forth.gr> References: <1541113468-22097-1-git-send-email-atish.patra@wdc.com> <866dedbc78ab4fa0e3b040697e112106@mailhost.ics.forth.gr> Message-ID: <20181106141331.GA28458@e107155-lin> To: linux-riscv@lists.infradead.org List-Id: linux-riscv.lists.infradead.org On Fri, Nov 02, 2018 at 08:58:39PM +0200, Nick Kossifidis wrote: > Hello All, > > ???? 2018-11-02 01:04, Atish Patra ??????: > > This patch series adds the cpu topology for RISC-V. It contains > > both the DT binding and actual source code. It has been tested on > > QEMU & Unleashed board. > > > > The idea is based on cpu-map in ARM with changes related to how > > we define SMT systems. The reason for adopting a similar approach > > to ARM as I feel it provides a very clear way of defining the > > topology compared to parsing cache nodes to figure out which cpus > > share the same package or core. I am open to any other idea to > > implement cpu-topology as well. > > > > I was also about to start a discussion about CPU topology on RISC-V > after the last swtools group meeting. The goal is to provide the > scheduler with hints on how to distribute tasks more efficiently > between harts, by populating the scheduling domain topology levels > (https://elixir.bootlin.com/linux/v4.19/ident/sched_domain_topology_level). > What we want to do is define cpu groups and assign them to > scheduling domains with the appropriate SD_ flags > (https://github.com/torvalds/linux/blob/master/include/linux/sched/topology.h#L16). > OK are we defining a CPU topology binding for Linux scheduler ? NACK for all the approaches that assumes any knowledge of OS scheduler. > So the cores that belong to a scheduling domain may share: > CPU capacity (SD_SHARE_CPUCAPACITY / SD_ASYM_CPUCAPACITY) > Package resources -e.g. caches, units etc- (SD_SHARE_PKG_RESOURCES) > Power domain (SD_SHARE_POWERDOMAIN) > Too Linux kernel/scheduler specific to be part of $subject > In this context I believe using words like "core", "package", > "socket" etc can be misleading. For example the sample topology you > use on the documentation says that there are 4 cores that are part > of a package, however "package" has a different meaning to the > scheduler. Also we don't say anything in case they share a power > domain or if they have the same capacity or not. This mapping deals > only with cache hierarchy or other shared resources. > {Un,}fortunately those are terms used by hardware people. > How about defining a dt scheme to describe the scheduler domain > topology levels instead ? e.g: > NACK as already mentioned above. -- Regards, Sudeep 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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 EFEF4C32789 for ; Tue, 6 Nov 2018 14:14:16 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id C1C2420685 for ; 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