From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline Date: Wed, 26 Jun 2013 10:29:48 -0700 Message-ID: <20130626172948.GD4405@mtj.dyndns.org> References: <20130625202452.16593.22810.stgit@srivatsabhat.in.ibm.com> <20130625202755.16593.67819.stgit@srivatsabhat.in.ibm.com> <20130625220026.GG3828@linux.vnet.ibm.com> <51CAF624.6060004@linux.vnet.ibm.com> <20130626143424.GN3828@linux.vnet.ibm.com> <1372258271.18733.256.camel@gandalf.local.home> <20130626152148.GA4405@mtj.dyndns.org> <1372260823.18733.263.camel@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: paulmck@linux.vnet.ibm.com, David Laight , "Srivatsa S. Bhat" , peterz@infradead.org, fweisbec@gmail.com, linux-kernel@vger.kernel.org, walken@google.com, mingo@kernel.org, linux-arch@vger.kernel.org, vincent.guittot@linaro.org, xiaoguangrong@linux.vnet.ibm.com, wangyun@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, namhyung@kernel.org, tglx@linutronix.de, laijs@cn.fujitsu.com, zhong@linux.vnet.ibm.com, netdev@vger.kernel.org, oleg@redhat.com, sbw@mit.edu, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org To: Steven Rostedt Return-path: Content-Disposition: inline In-Reply-To: <1372260823.18733.263.camel@gandalf.local.home> Sender: linux-arch-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hello, On Wed, Jun 26, 2013 at 11:33:43AM -0400, Steven Rostedt wrote: > I thought the whole deal with this patchset was to remove stop_machine > from CPU hotplug. Why halt all CPUs just to remove one? stomp_machine() > is extremely intrusive for the entire system, where as one CPU making > sure all CPUs schedule isn't very intrusive at all. > > I didn't think the idea of this patch set was to make CPU hotplug > faster, just less intrusive to the system. Yeap, removal of stop_machine is a great improvement in itself. ISTR mentions of hot-unplug latency but I could be mistaken. Srivatsa, can you please chime in on that? Thanks. -- tejun