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 87717C4332F for ; Thu, 10 Feb 2022 19:27:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343976AbiBJT1Z (ORCPT ); Thu, 10 Feb 2022 14:27:25 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:60040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343947AbiBJT1V (ORCPT ); Thu, 10 Feb 2022 14:27:21 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 33668115A for ; Thu, 10 Feb 2022 11:27:22 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1644521241; 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=GNtwi8xnD/wpxMJkxYRgc+GcsRTLVGTfs9JYaKnP9Qg=; b=Xj47WjX8EdLO60xj3lY+608dTfJo2xaS5Nu4ydBnQHYkbm+swdg7EH3wtKMlY5Z9lCMWSo wSt4xG/TJZpYF/9AKrvIXdpnXheEadVP519jbrwDv+bx4LavfiA+p5OcTG0sZjkh9osDRz QUKpoMiB3z6DnCheNl7DTitBxEgj0aA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-590-rLoL6nCFOp2CnnYG8WrfgQ-1; Thu, 10 Feb 2022 14:27:18 -0500 X-MC-Unique: rLoL6nCFOp2CnnYG8WrfgQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4E5AB46861; Thu, 10 Feb 2022 19:27:15 +0000 (UTC) Received: from [10.22.19.255] (unknown [10.22.19.255]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3B8EE5E482; Thu, 10 Feb 2022 19:27:12 +0000 (UTC) Message-ID: <52de2e14-33d9-bdda-4b37-3e72ae9954c7@redhat.com> Date: Thu, 10 Feb 2022 14:27:11 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [RFC 00/12] locking: Separate lock tracepoints from lockdep/lock_stat (v1) Content-Language: en-US To: paulmck@kernel.org, Peter Zijlstra Cc: Namhyung Kim , Ingo Molnar , Will Deacon , Boqun Feng , LKML , Thomas Gleixner , Steven Rostedt , Byungchul Park , Mathieu Desnoyers , Radoslaw Burny , Tejun Heo , rcu , cgroups , linux-btrfs , intel-gfx References: <20220208184208.79303-1-namhyung@kernel.org> <20220209090908.GK23216@worktop.programming.kicks-ass.net> <20220210191404.GM4285@paulmck-ThinkPad-P17-Gen-1> From: Waiman Long In-Reply-To: <20220210191404.GM4285@paulmck-ThinkPad-P17-Gen-1> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/10/22 14:14, Paul E. McKenney wrote: > On Thu, Feb 10, 2022 at 10:13:53AM +0100, Peter Zijlstra wrote: >> On Wed, Feb 09, 2022 at 04:32:58PM -0800, Namhyung Kim wrote: >>> On Wed, Feb 9, 2022 at 1:09 AM Peter Zijlstra wrote: >>>> On Tue, Feb 08, 2022 at 10:41:56AM -0800, Namhyung Kim wrote: >>>> >>>>> Eventually I'm mostly interested in the contended locks only and I >>>>> want to reduce the overhead in the fast path. By moving that, it'd be >>>>> easy to track contended locks with timing by using two tracepoints. >>>> So why not put in two new tracepoints and call it a day? >>>> >>>> Why muck about with all that lockdep stuff just to preserve the name >>>> (and in the process continue to blow up data structures etc..). This >>>> leaves distros in a bind, will they enable this config and provide >>>> tracepoints while bloating the data structures and destroying things >>>> like lockref (which relies on sizeof(spinlock_t)), or not provide this >>>> at all. >>> If it's only lockref, is it possible to change it to use arch_spinlock_t >>> so that it can remain in 4 bytes? It'd be really nice if we can keep >>> spin lock size, but it'd be easier to carry the name with it for >>> analysis IMHO. >> It's just vile and disgusting to blow up the lock size for convenience >> like this. >> >> And no, there's more of that around. A lot of effort has been spend to >> make sure spinlocks are 32bit and we're not going to give that up for >> something as daft as this. >> >> Just think harder on the analysis side. Like said; I'm thinking the >> caller IP should be good enough most of the time. > Another option is to keep any additional storage in a separate data > structure keyed off of lock address, lockdep class, or whatever. > > Whether or not this is a -good- option, well, who knows? ;-) I have suggested that too. Unfortunately, I was replying to an email with your wrong email address. So you might not have received it. Cheers, Longman