From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: [PATCH] sched/rt: don't try to balance rt_runtime when it is futile Date: Thu, 15 May 2014 19:27:21 +0200 Message-ID: <1400174841.18229.6.camel@marge.simpson.net> References: <1400080115-12339-1-git-send-email-paul.gortmaker@windriver.com> <20140514154459.GE4570@linux.vnet.ibm.com> <1400123931.5175.38.camel@marge.simpson.net> <20140515144553.GZ4570@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Paul Gortmaker , linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Steven Rostedt , Thomas Gleixner To: paulmck@linux.vnet.ibm.com Return-path: In-Reply-To: <20140515144553.GZ4570@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Thu, 2014-05-15 at 07:45 -0700, Paul E. McKenney wrote: > On Thu, May 15, 2014 at 05:18:51AM +0200, Mike Galbraith wrote: > > On Wed, 2014-05-14 at 08:44 -0700, Paul E. McKenney wrote: > > > > > In practice, not sure how much testing CONFIG_NO_HZ_FULL=y has received > > > for -rt kernels in production environments. > > > > I took 3.14-rt out for a quick spin on my 64 core box, it didn't work at > > all with 60 cores isolated. I didn't have time to rummage, but it looks > > like there are still bugs to squash. > > > > Biggest problem with CONFIG_NO_HZ_FULL is the price tag. It just raped > > fast mover performance last time I measured. > > I do have a report of the RCU grace-period kthreads (rcu_preempt, > rcu_sched, and rcu_bh) consuming excessive CPU time on large boxes, > but this is for workloads with lots of threads and context switches. > > Whether relevant or not to your situation, working on it... RCU signal was swamped by accounting. -Mike