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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,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 32A71C433E0 for ; Wed, 8 Jul 2020 23:53:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08A7220659 for ; Wed, 8 Jul 2020 23:53:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Z9KU3zov" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726228AbgGHXxN (ORCPT ); Wed, 8 Jul 2020 19:53:13 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:24358 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726107AbgGHXxN (ORCPT ); Wed, 8 Jul 2020 19:53:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594252392; 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=sMGK9tA8COwKvD1fQVNRk+JUOzHjOS5PJXHcnsRB2BQ=; b=Z9KU3zovTYCTfHlzhHGTscdQEybWoz3LF0b4CVzqjR88yJda4jrOWQhZS3Gu0Jwlkz/feL Yq3i3jNM+Xs09sh8zjvMQJG8Jh0843gPlV2x59INhjZNdUMpS9/S7ttxSLjQSOy8ZEEidB u5nQZ23MDPPwOvlrRgVG/tMopufwAek= 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-460-PttZH5YuNPOhfnms_liwDg-1; Wed, 08 Jul 2020 19:53:08 -0400 X-MC-Unique: PttZH5YuNPOhfnms_liwDg-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 30B6F1082; Wed, 8 Jul 2020 23:53:06 +0000 (UTC) Received: from llong.remote.csb (ovpn-116-205.rdu2.redhat.com [10.10.116.205]) by smtp.corp.redhat.com (Postfix) with ESMTP id EA6637F8A4; Wed, 8 Jul 2020 23:53:04 +0000 (UTC) Subject: Re: [PATCH v3 0/6] powerpc: queued spinlocks and rwlocks To: Peter Zijlstra Cc: Nicholas Piggin , linuxppc-dev@lists.ozlabs.org, Anton Blanchard , Boqun Feng , kvm-ppc@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , virtualization@lists.linux-foundation.org, Will Deacon References: <20200706043540.1563616-1-npiggin@gmail.com> <24f75d2c-60cd-2766-4aab-1a3b1c80646e@redhat.com> <1594101082.hfq9x5yact.astroid@bobo.none> <20200708083210.GD597537@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: <72f7df33-ab58-2e58-7981-cf02b6638c5b@redhat.com> Date: Wed, 8 Jul 2020 19:53:04 -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: <20200708083210.GD597537@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 7/8/20 4:32 AM, Peter Zijlstra wrote: > On Tue, Jul 07, 2020 at 11:33:45PM -0400, Waiman Long wrote: >> From 5d7941a498935fb225b2c7a3108cbf590114c3db Mon Sep 17 00:00:00 2001 >> From: Waiman Long >> Date: Tue, 7 Jul 2020 22:29:16 -0400 >> Subject: [PATCH 2/9] locking/pvqspinlock: Introduce >> CONFIG_PARAVIRT_QSPINLOCKS_LITE >> >> Add a new PARAVIRT_QSPINLOCKS_LITE config option that allows >> architectures to use the PV qspinlock code without the need to use or >> implement a pv_kick() function, thus eliminating the atomic unlock >> overhead. The non-atomic queued_spin_unlock() can be used instead. >> The pv_wait() function will still be needed, but it can be a dummy >> function. >> >> With that option set, the hybrid PV queued/unfair locking code should >> still be able to make it performant enough in a paravirtualized > How is this supposed to work? If there is no kick, you have no control > over who wakes up and fairness goes out the window entirely. > > You don't even begin to explain... > I don't have a full understanding of how the PPC hypervisor work myself. Apparently, a cpu kick may not be needed. This is just a test patch to see if it yields better result. It is subjected to further modifcation. Cheers, Longman