From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [GIT RFC PULL rcu/urgent] Prevent Kconfig from asking pointless questions Date: Mon, 20 Apr 2015 14:15:04 -0700 Message-ID: <20150420211504.GW5561@linux.vnet.ibm.com> References: <20150416183812.GA5571@linux.vnet.ibm.com> <20150418130340.GA26931@gmail.com> <20150418133444.GD23685@linux.vnet.ibm.com> <20150418143238.GA2337@gmail.com> <20150419020541.GA5561@linux.vnet.ibm.com> <20150420113554.598e503f@sluggy> <20150420170902.GU5561@linux.vnet.ibm.com> <20150420204049.GF24936@home.goodmis.org> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Clark Williams , Ingo Molnar , linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, a.p.zijlstra@chello.nl, akpm@linux-foundation.org, linux-rt-users@vger.kernel.org To: Steven Rostedt Return-path: Received: from e33.co.us.ibm.com ([32.97.110.151]:43220 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752039AbbDTVPK (ORCPT ); Mon, 20 Apr 2015 17:15:10 -0400 Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 20 Apr 2015 15:15:10 -0600 Content-Disposition: inline In-Reply-To: <20150420204049.GF24936@home.goodmis.org> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Mon, Apr 20, 2015 at 04:40:49PM -0400, Steven Rostedt wrote: > On Mon, Apr 20, 2015 at 10:09:03AM -0700, Paul E. McKenney wrote: > > > > The sysfs knob might be nice, but as far as I know nobody has been > > complaining about it. > > > > Besides, we already have the rcutree.kthread_prio= kernel-boot parameter. > > So how about if the Kconfig parameter selects either SCHED_OTHER > > (the default) or SCHED_FIFO:1, and then the boot parameter can be used > > to select other values. > > Hmm, what priority is this for anyway. To change the priority of the boost > value at run time, do we only need to change the priority of the rcub threads? > > And the priority of the other rcu threads can change as well with a simple > chrt? > > If that's the case, then we don't need a sysctl knob at all. For the grace-period kthreads and the boost kthread, that is the case. It is also the case for the per-CPU kthreads that invoke RCU callbacks for the non-offloaded RCU_BOOST configuration (and that replace all softirq RCU work in -rt). So, should I just ditch all of the priority-setting within RCU and tell users to just use chrt? Thanx, Paul