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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 646FCC43382 for ; Fri, 28 Sep 2018 18:33:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 26F4C20685 for ; Fri, 28 Sep 2018 18:33:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 26F4C20685 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726738AbeI2A6o convert rfc822-to-8bit (ORCPT ); Fri, 28 Sep 2018 20:58:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36204 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726145AbeI2A6o (ORCPT ); Fri, 28 Sep 2018 20:58:44 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E3977C0578FA; Fri, 28 Sep 2018 18:33:41 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-8.bos.redhat.com [10.18.17.8]) by smtp.corp.redhat.com (Postfix) with ESMTP id A41584DA8E; Fri, 28 Sep 2018 18:33:40 +0000 (UTC) Subject: Re: [PATCH v2 2/2] debugobjects: Disable lockdep tracking of debugobjects internal locks From: Waiman Long To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , Will Deacon , linux-kernel@vger.kernel.org, Yang Shi , Arnd Bergmann , chuhu@redhat.com References: <1537886469-18227-1-git-send-email-longman@redhat.com> <1537886469-18227-3-git-send-email-longman@redhat.com> <20180925153241.GD29985@hirez.programming.kicks-ass.net> <20180925163150.GE29985@hirez.programming.kicks-ass.net> Organization: Red Hat Message-ID: <52e6048f-c361-e6bc-7840-a55bbd30416f@redhat.com> Date: Fri, 28 Sep 2018 14:33:40 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 28 Sep 2018 18:33:42 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/25/2018 12:36 PM, Waiman Long wrote: > On 09/25/2018 12:31 PM, Peter Zijlstra wrote: >> Also, where is the performance benefit here. The normal lock_acquire >> path doesn't change gobal state (it will not see new lock ordering in >> 99%+ of the cases). >> >> Typically we only push the lock on the task local lock stack, compute >> the new hash, and do the hash lookup, find it already exists and return. >> >> So what is the expensive part, and can we do something about that? > I will need to do some experimentation to find out. Will update this > thread with my finding. > I have sent out a patchset on improving lockdep performance that hopefully will help to alleviate the problems that I saw. I still have other ideas about further changes I want to investigate, but that will wait until I am done with the current lockdep patchset. -Longman