From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [RFC PATCH-tip v4 10/10] locking/rwsem: Add a boot parameter to reader spinning threshold Date: Wed, 24 Aug 2016 14:39:11 -0400 Message-ID: <57BDE9CF.5030801@hpe.com> References: <1471554672-38662-1-git-send-email-Waiman.Long@hpe.com> <1471554672-38662-11-git-send-email-Waiman.Long@hpe.com> <20160824040007.GA17186@linux-80c1.suse> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20160824040007.GA17186@linux-80c1.suse> Sender: linux-kernel-owner@vger.kernel.org To: Davidlohr Bueso Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, Jason Low , Dave Chinner , Jonathan Corbet , Scott J Norton , Douglas Hatch List-Id: linux-arch.vger.kernel.org On 08/24/2016 12:00 AM, Davidlohr Bueso wrote: > On Thu, 18 Aug 2016, Waiman Long wrote: > >> The default reader spining threshold is current set to 4096. However, >> the right reader spinning threshold may vary from one system to >> another and among the different architectures. This patch adds a new >> kernel boot parameter to modify the threshold value. This enables >> better tailoring to the needs of different systems as well as for >> testing purposes. > > It also means that those systems could very easily be incorrectly > tailored. > (and worse case scenario: reboot, is obviously a terrible way to get rid > of any issues). I very much disagree with exposing this sort of core > stuff, > it should work well for everyone out of the box, not relying on users to > properly configure this. > > Thanks, > Davidlohr I also have some concern about exposing this kernel parameter as it will be hard to tune. That is why I put it at the end to gauge the opinion of others. I will leave this out when I send out the next version. Cheers, Longman From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-dm3nam03on0123.outbound.protection.outlook.com ([104.47.41.123]:27136 "EHLO NAM03-DM3-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754192AbcHXSjz (ORCPT ); Wed, 24 Aug 2016 14:39:55 -0400 Message-ID: <57BDE9CF.5030801@hpe.com> Date: Wed, 24 Aug 2016 14:39:11 -0400 From: Waiman Long MIME-Version: 1.0 Subject: Re: [RFC PATCH-tip v4 10/10] locking/rwsem: Add a boot parameter to reader spinning threshold References: <1471554672-38662-1-git-send-email-Waiman.Long@hpe.com> <1471554672-38662-11-git-send-email-Waiman.Long@hpe.com> <20160824040007.GA17186@linux-80c1.suse> In-Reply-To: <20160824040007.GA17186@linux-80c1.suse> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Davidlohr Bueso Cc: Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-s390@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, Jason Low , Dave Chinner , Jonathan Corbet , Scott J Norton , Douglas Hatch Message-ID: <20160824183911.f_0i0hMdroZAutEjMpUHWZUapLCl7q0WeaYL9MyOqSA@z> On 08/24/2016 12:00 AM, Davidlohr Bueso wrote: > On Thu, 18 Aug 2016, Waiman Long wrote: > >> The default reader spining threshold is current set to 4096. However, >> the right reader spinning threshold may vary from one system to >> another and among the different architectures. This patch adds a new >> kernel boot parameter to modify the threshold value. This enables >> better tailoring to the needs of different systems as well as for >> testing purposes. > > It also means that those systems could very easily be incorrectly > tailored. > (and worse case scenario: reboot, is obviously a terrible way to get rid > of any issues). I very much disagree with exposing this sort of core > stuff, > it should work well for everyone out of the box, not relying on users to > properly configure this. > > Thanks, > Davidlohr I also have some concern about exposing this kernel parameter as it will be hard to tune. That is why I put it at the end to gauge the opinion of others. I will leave this out when I send out the next version. Cheers, Longman