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 3E114C47089 for ; Thu, 17 Nov 2022 17:19:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239727AbiKQRTn (ORCPT ); Thu, 17 Nov 2022 12:19:43 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44482 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240428AbiKQRTS (ORCPT ); Thu, 17 Nov 2022 12:19:18 -0500 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF793B484; Thu, 17 Nov 2022 09:19:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1668705551; bh=KMEPzgA4+nFQ6spk6DMrmsDE0IEPA0Y7GRAKqbdxzdU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Oc+3+oJhcCC3FNxKERBuxiqANUEg4fT9qNngNH3c8mdEvQb6axXNcJNSkqzOfnUJW IqpZZaZQX658iKHXCng6NYy9Xk8KeYaTNt3BbrwiYPWHXRwq9aw3cMhpuflOcq1n68 qXdRftroikkTvIbw8nwuZ0k6du5zxCswjFSv5wO5QDeLW/KTHwU3es0v0B+xYzNdZp ruAO2zIkQvIS6AisFh0+T2Q3E2IFsdScYupJpKmszY/w5SpOsdAePiZzP3Rvqlg+TN xHznIBCKUAoqYoj64RebzhkBD/Vywz9jShPheP7BsVpLLJZHjAJLFlRN8KZwGBSWgZ pZ0KcGHQEPglw== Received: from [172.16.0.153] (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4NCmqL5mcxzWty; Thu, 17 Nov 2022 12:19:10 -0500 (EST) Message-ID: <273f4883-25bc-44ad-9c35-3950ca8a3fcf@efficios.com> Date: Thu, 17 Nov 2022 12:19:22 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: [PATCH v5 08/24] sched: Introduce per memory space current virtual cpu id Content-Language: en-US To: Sean Christopherson Cc: Andy Lutomirski , Peter Zijlstra , linux-kernel@vger.kernel.org, Thomas Gleixner , "Paul E . McKenney" , Boqun Feng , "H . Peter Anvin" , Paul Turner , linux-api@vger.kernel.org, Christian Brauner , Florian Weimer , David.Laight@aculab.com, carlos@redhat.com, Peter Oskolkov , Alexander Mikhalitsyn , Chris Kennelly References: <20221103200359.328736-1-mathieu.desnoyers@efficios.com> <20221103200359.328736-9-mathieu.desnoyers@efficios.com> <2f191ddb-de89-52c0-e7da-26ac0239b8fe@efficios.com> From: Mathieu Desnoyers In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022-11-14 15:49, Sean Christopherson wrote: > On Fri, Nov 11, 2022, Mathieu Desnoyers wrote: >> On 2022-11-10 23:41, Andy Lutomirski wrote: >>> On Thu, Nov 3, 2022 at 1:05 PM Mathieu Desnoyers >>> wrote: >>> Also, in my mind "virtual cpu" is vCPU, which this isn't. Maybe >>> "compacted cpu" or something? It's a strange sort of concept. >> >> I've kept the same wording that has been introduced in 2011 by Paul Turner >> and used internally at Google since then, although it may be confusing if >> people expect kvm-vCPU and rseq-vcpu to mean the same thing. Both really end >> up providing the semantic of a virtually assigned cpu id (in opposition to >> the logical cpu id on the system), but this is much more involved in the >> case of KVM. > > I had the same reaction as Andy. The rseq concepts don't worry me so much as the > existence of "vcpu" in mm_struct/task_struct, e.g. switch_mm_vcpu() when switching > between KVM vCPU tasks is going to be super confusing. Ditto for mm_vcpu_get() > and mm_vcpu_put() in the few cases where KVM currently does mmget()/mmput(). I'm fine with changing the wording if it helps make things less confusing. Should we go for "compact-cpu-id" ? "packed-cpu-id" ? Other ideas ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com