From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754188AbdJLMFj convert rfc822-to-8bit (ORCPT ); Thu, 12 Oct 2017 08:05:39 -0400 Received: from ozlabs.org ([103.22.144.67]:53605 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdJLMFi (ORCPT ); Thu, 12 Oct 2017 08:05:38 -0400 From: Michael Ellerman To: Anju T Sudhakar , Stewart Smith Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, maddy@linux.vnet.ibm.com, hemant@linux.vnet.ibm.com Subject: Re: [PATCH] powerpc/powernv: Add kernel cmdline parameter to disable imc In-Reply-To: <06fe39eb-d5fe-4472-56b4-f66390d7fad9@linux.vnet.ibm.com> References: <1507531597-25947-1-git-send-email-anju@linux.vnet.ibm.com> <87wp43wf2v.fsf@concordia.ellerman.id.au> <87infmeonf.fsf@linux.vnet.ibm.com> <06fe39eb-d5fe-4472-56b4-f66390d7fad9@linux.vnet.ibm.com> Date: Thu, 12 Oct 2017 23:05:36 +1100 Message-ID: <87r2u8tvu7.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Anju T Sudhakar writes: > Hi mpe, stewart, > > > On Wednesday 11 October 2017 01:55 AM, Stewart Smith wrote: >> Michael Ellerman writes: >>> Anju T Sudhakar writes: >>> >>>> Add a kernel command line parameter option to disable In-Memory Collection >>>> (IMC) counters and add documentation. This helps in debug. >>> I'd really rather we didn't. Do we *really* need this? >>> >>> We don't have command line parameters to disable any of the other ~20 >>> PMUs, why is this one special? > > This one is really helpful in debugging, incase if we want to proceed > without nest counters  OR > core counters . But if we have the facility to do the same from > petitboot, its fine. I understand it's helpful for debugging. But we can't afford to have a command line option to disable every ~1K SLOC of code. If there's a compelling reason why we need to disable IMC *on production systems* - then a command line option is a possibility. Though really if there is a compelling reason for that maybe we have bigger problems :) This is also a very new driver, so we're still finding some bugs, in a few months it should be more stable and then the command line option will just be cruft. cheers