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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 485A0C433E0 for ; Thu, 23 Jul 2020 19:04:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1FE9F2067D for ; Thu, 23 Jul 2020 19:04:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TGG0Tm6k" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728081AbgGWTEV (ORCPT ); Thu, 23 Jul 2020 15:04:21 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:33714 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726425AbgGWTEV (ORCPT ); Thu, 23 Jul 2020 15:04:21 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595531060; h=from:from: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=To+9baHo0nhSErT6A7uWNDfbadEXVch0SXRcbjuvNmc=; b=TGG0Tm6kej68GGZK1dM47exRgAoxyWHr2NIfVXC28jRMJIrl4rGdaQ0Z62aSK/EUUEgpOE zE/H39vbor56wfxEXXlDq2xkwQqv4nys6gA6MqMsINdE3lPxSqeEV/wZznRmjEWztIAnoQ TScViLoBZRssv2CTItiyluvlJrrf1Qk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-408-KMn91B7pP3-wvEpB_u563g-1; Thu, 23 Jul 2020 15:04:16 -0400 X-MC-Unique: KMn91B7pP3-wvEpB_u563g-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 289D4106B243; Thu, 23 Jul 2020 19:04:15 +0000 (UTC) Received: from llong.remote.csb (ovpn-119-128.rdu2.redhat.com [10.10.119.128]) by smtp.corp.redhat.com (Postfix) with ESMTP id C45565BAD5; Thu, 23 Jul 2020 19:04:13 +0000 (UTC) Subject: Re: [PATCH v3 5/6] powerpc/pseries: implement paravirt qspinlocks for SPLPAR To: peterz@infradead.org Cc: Michael Ellerman , Nicholas Piggin , linuxppc-dev@lists.ozlabs.org, Will Deacon , Boqun Feng , Ingo Molnar , Anton Blanchard , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org References: <20200706043540.1563616-1-npiggin@gmail.com> <20200706043540.1563616-6-npiggin@gmail.com> <874kqhvu1v.fsf@mpe.ellerman.id.au> <8265d782-4e50-a9b2-a908-0cb588ffa09c@redhat.com> <20200723140011.GR5523@worktop.programming.kicks-ass.net> <845de183-56f5-2958-3159-faa131d46401@redhat.com> <20200723184759.GS119549@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: <6d6279ad-7432-63c1-14c3-18c4cff30bf8@redhat.com> Date: Thu, 23 Jul 2020 15:04:13 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200723184759.GS119549@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/23/20 2:47 PM, peterz@infradead.org wrote: > On Thu, Jul 23, 2020 at 02:32:36PM -0400, Waiman Long wrote: >> BTW, do you have any comment on my v2 lock holder cpu info qspinlock patch? >> I will have to update the patch to fix the reported 0-day test problem, but >> I want to collect other feedback before sending out v3. > I want to say I hate it all, it adds instructions to a path we spend an > aweful lot of time optimizing without really getting anything back for > it. It does add some extra instruction that may slow it down slightly, but I don't agree that it gives nothing back. The cpu lock holder information can be useful in analyzing crash dumps and in some debugging situation. I think it can be useful in RHEL for this readon. How about an x86 config option to allow distros to decide if they want to have it enabled? I will make sure that it will have no performance degradation if the option is not enabled. Cheers, Longman