From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Tue, 9 Oct 2018 16:58:18 +0100 Subject: [PATCH] Doc: lockdep: add information about performance impact In-Reply-To: <20181009154359.GB5728@hirez.programming.kicks-ass.net> References: <20181009153935eucas1p2dec146575ed5fefd4a0b2b6cb9bac056~b_ujkjRd31303013030eucas1p2C@eucas1p2.samsung.com> <20181009154359.GB5728@hirez.programming.kicks-ass.net> Message-ID: <20181009155818.GD9259@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Oct 09, 2018 at 05:43:59PM +0200, Peter Zijlstra wrote: > On Tue, Oct 09, 2018 at 05:39:27PM +0200, Lukasz Luba wrote: > > This patch add some warning related to performance drop. > > It should be mentioned that this is not for free > > and the platfrom resources (cache, bus interconnect, etc.) > > will be used more frequently. > > To me this reads a bit like: water is wet. > > Is this really needed? I don't think so -- this is a debug option under "kernel hacking". Surely the perf hit comes with the territory. Will 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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 31737C64EB8 for ; Tue, 9 Oct 2018 15:58:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 01A372087D for ; Tue, 9 Oct 2018 15:58:22 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01A372087D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.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 S1726830AbeJIXPz (ORCPT ); Tue, 9 Oct 2018 19:15:55 -0400 Received: from foss.arm.com ([217.140.101.70]:40850 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726418AbeJIXPy (ORCPT ); Tue, 9 Oct 2018 19:15:54 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 58F0B80D; Tue, 9 Oct 2018 08:58:19 -0700 (PDT) Received: from edgewater-inn.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 28DA43F5D3; Tue, 9 Oct 2018 08:58:19 -0700 (PDT) Received: by edgewater-inn.cambridge.arm.com (Postfix, from userid 1000) id 7BA991AE0B3B; Tue, 9 Oct 2018 16:58:18 +0100 (BST) Date: Tue, 9 Oct 2018 16:58:18 +0100 From: Will Deacon To: Peter Zijlstra Cc: Lukasz Luba , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, b.zolnierkie@samsung.com, mingo@redhat.com, corbet@lwn.net Subject: Re: [PATCH] Doc: lockdep: add information about performance impact Message-ID: <20181009155818.GD9259@arm.com> References: <20181009153935eucas1p2dec146575ed5fefd4a0b2b6cb9bac056~b_ujkjRd31303013030eucas1p2C@eucas1p2.samsung.com> <20181009154359.GB5728@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181009154359.GB5728@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 09, 2018 at 05:43:59PM +0200, Peter Zijlstra wrote: > On Tue, Oct 09, 2018 at 05:39:27PM +0200, Lukasz Luba wrote: > > This patch add some warning related to performance drop. > > It should be mentioned that this is not for free > > and the platfrom resources (cache, bus interconnect, etc.) > > will be used more frequently. > > To me this reads a bit like: water is wet. > > Is this really needed? I don't think so -- this is a debug option under "kernel hacking". Surely the perf hit comes with the territory. Will