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 75660C35247 for ; Tue, 4 Feb 2020 17:39:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4883520674 for ; Tue, 4 Feb 2020 17:39:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="UBiHX1t+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727478AbgBDRjk (ORCPT ); Tue, 4 Feb 2020 12:39:40 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:26421 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727382AbgBDRjk (ORCPT ); Tue, 4 Feb 2020 12:39:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580837978; 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=rOt4Q7Y7NbeoLNOkgoGRXQ71dvuW8UbbyvbNZ5N5pIs=; b=UBiHX1t+4ROu0VQf6U/i5XkZvi1+z9soqjU5GuTxQf8REepOUjIcsdIGitFmQ0zxD1/4RW 3PSGbMjR4AGs0DdDlYFA1ohVxEY2NAuDZseKHcF6jmH8r12Zn1Xa2PUmZsWOv5I7jJqdAM 0uFcMFoxSso9ciRpF9dzeEfeUTkyA8Y= 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-233-RFdFYVoNOtmfFcl0m6Qxsg-1; Tue, 04 Feb 2020 12:39:36 -0500 X-MC-Unique: RFdFYVoNOtmfFcl0m6Qxsg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BE0AADB25; Tue, 4 Feb 2020 17:39:33 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-59.bos.redhat.com [10.18.17.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id 17A5660BF4; Tue, 4 Feb 2020 17:39:30 +0000 (UTC) Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA To: Peter Zijlstra , Alex Kogan Cc: linux@armlinux.org.uk, Ingo Molnar , Will Deacon , Arnd Bergmann , linux-arch@vger.kernel.org, linux-arm-kernel , linux-kernel@vger.kernel.org, Thomas Gleixner , Borislav Petkov , hpa@zytor.com, x86@kernel.org, Hanjun Guo , Jan Glauber , Steven Sistare , Daniel Jordan , dave.dice@oracle.com References: <8D3AFB47-B595-418C-9568-08780DDC58FF@oracle.com> <714892cd-d96f-4d41-ae8b-d7b7642a6e3c@redhat.com> <1669BFDE-A1A5-4ED8-B586-035460BBF68A@oracle.com> <20200125111931.GW11457@worktop.programming.kicks-ass.net> <20200203134540.GA14879@hirez.programming.kicks-ass.net> <6d11b22b-2fb5-7dea-f88b-b32f1576a5e0@redhat.com> <20200203152807.GK14914@hirez.programming.kicks-ass.net> <15fa978d-bd41-3ecb-83d5-896187e11244@redhat.com> <83762715-F68C-42DF-9B41-C4C48DF6762F@oracle.com> <20200204172758.GF14879@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: Date: Tue, 4 Feb 2020 12:39:30 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20200204172758.GF14879@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/4/20 12:27 PM, Peter Zijlstra wrote: > On Tue, Feb 04, 2020 at 11:54:02AM -0500, Alex Kogan wrote: >>> On Feb 3, 2020, at 10:47 AM, Waiman Long wrote: >>> >>> On 2/3/20 10:28 AM, Peter Zijlstra wrote: >>>> On Mon, Feb 03, 2020 at 09:59:12AM -0500, Waiman Long wrote: >>>>> On 2/3/20 8:45 AM, Peter Zijlstra wrote: >>>>>> Presumably you have a workload where CNA is actually a win? That i= s, >>>>>> what inspired you to go down this road? Which actual kernel lock i= s so >>>>>> contended on NUMA machines that we need to do this? >> There are quite a few actually. files_struct.file_lock, file_lock_cont= ext.flc_lock >> and lockref.lock are some concrete examples that get very hot in will-= it-scale >> benchmarks.=20 > Right, that's all a variant of banging on the same resources across > nodes. I'm not sure there's anything fundamental we can fix there. > >> And then there are spinlocks in __futex_data.queues,=20 >> which get hot when applications have contended (pthread) locks =E2=80=94= =20 >> LevelDB is an example. > A numa aware rework of futexes has been on the todo list for years :/ Now, we are going to get that for free with this patchset:-) > >> Our initial motivation was based on an observation that kernel qspinlo= ck is not=20 >> NUMA-aware. So what, you may ask. Much like people realized in the pas= t that >> global spinning is bad for performance, and they switched from ticket = lock to >> locks with local spinning (e.g., MCS), I think everyone would agree th= ese days that >> bouncing a lock (and cache lines in general) across numa nodes is simi= larly bad. >> And as CNA demonstrates, we are easily leaving 2-3x speedups on the ta= ble by >> doing just that with the current qspinlock. > Actual benchmarks with performance numbers are required. It helps > motivate the patches as well as gives reviewers clues on how to > reproduce / inspect the claims made. > I think the cover-letter does have some benchmark results listed.=C2=A0 A= re you saying that some benchmark results should be put into individual patches themselves? Cheers, Longman