From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH] sched/rt: don't try to balance rt_runtime when it is futile Date: Sun, 18 May 2014 08:58:15 -0700 Message-ID: <20140518155815.GK4570@linux.vnet.ibm.com> References: <1400080115-12339-1-git-send-email-paul.gortmaker@windriver.com> <20140514154459.GE4570@linux.vnet.ibm.com> <1400123931.5175.38.camel@marge.simpson.net> <1400386954.5140.36.camel@marge.simpson.net> <20140518052039.GF4570@linux.vnet.ibm.com> <1400402201.5166.13.camel@marge.simpson.net> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Paul Gortmaker , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Steven Rostedt , Thomas Gleixner To: Mike Galbraith Return-path: Content-Disposition: inline In-Reply-To: <1400402201.5166.13.camel@marge.simpson.net> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Sun, May 18, 2014 at 10:36:41AM +0200, Mike Galbraith wrote: > On Sat, 2014-05-17 at 22:20 -0700, Paul E. McKenney wrote: > > > If you are saying that turning on nohz_full doesn't help unless you > > also ensure that there is only one runnable task per CPU, I completely > > agree. If you are saying something else, you lost me. ;-) > > Yup, that's it more or less. It's not only single task loads that could > benefit from better isolation, but if isolation improving measures are > tied to nohz_full, other sensitive loads will suffer if they try to use > isolation improvements. So you are arguing for a separate Kconfig variable that does the isolation? So that NO_HZ_FULL selects this new variable, and (for example) RCU uses this new variable to decide when to pin the grace-period kthreads onto the housekeeping CPU? Thanx, Paul