From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: Re: [PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline Date: Wed, 26 Jun 2013 23:58:48 +0530 Message-ID: <51CB32E0.3040106@linux.vnet.ibm.com> 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> <20130626172948.GD4405@mtj.dyndns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130626172948.GD4405@mtj.dyndns.org> Sender: linux-pm-owner@vger.kernel.org To: Tejun Heo Cc: Steven Rostedt , peterz@infradead.org, fweisbec@gmail.com, oleg@redhat.com, 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, paulmck@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, linux-kernel@vger.kernel.org, sbw@mit.edu, David Laight , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org List-Id: linux-arch.vger.kernel.org On 06/26/2013 10:59 PM, Tejun Heo wrote: > 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. Absolutely. To make hotplug less intrusive on the system. > ISTR > mentions of hot-unplug latency but I could be mistaken. Srivatsa, can > you please chime in on that? > Yes, we were discussing hot-unplug latency for use-cases such as suspend/resume. We didn't want to make those operations slower in the process of removing stop_machine() from hotplug. Regards, Srivatsa S. Bhat From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e28smtp05.in.ibm.com (e28smtp05.in.ibm.com [122.248.162.5]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "e28smtp05.in.ibm.com", Issuer "GeoTrust SSL CA" (not verified)) by ozlabs.org (Postfix) with ESMTPS id 1C4852C008E for ; Thu, 27 Jun 2013 04:32:11 +1000 (EST) Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 26 Jun 2013 23:57:03 +0530 Received: from d28relay05.in.ibm.com (d28relay05.in.ibm.com [9.184.220.62]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 040FD3940043 for ; Thu, 27 Jun 2013 00:02:04 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay05.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r5QIW0BC29163716 for ; Thu, 27 Jun 2013 00:02:01 +0530 Received: from d28av04.in.ibm.com (loopback [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r5QIW2gN019359 for ; Thu, 27 Jun 2013 04:32:04 +1000 Message-ID: <51CB32E0.3040106@linux.vnet.ibm.com> Date: Wed, 26 Jun 2013 23:58:48 +0530 From: "Srivatsa S. Bhat" MIME-Version: 1.0 To: Tejun Heo Subject: Re: [PATCH v2 15/45] rcu: Use get/put_online_cpus_atomic() to prevent CPU offline 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> <20130626172948.GD4405@mtj.dyndns.org> In-Reply-To: <20130626172948.GD4405@mtj.dyndns.org> Content-Type: text/plain; charset=ISO-8859-1 Cc: 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, paulmck@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org, rusty@rustcorp.com.au, Steven Rostedt , 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, David Laight , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 06/26/2013 10:59 PM, Tejun Heo wrote: > 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. Absolutely. To make hotplug less intrusive on the system. > ISTR > mentions of hot-unplug latency but I could be mistaken. Srivatsa, can > you please chime in on that? > Yes, we were discussing hot-unplug latency for use-cases such as suspend/resume. We didn't want to make those operations slower in the process of removing stop_machine() from hotplug. Regards, Srivatsa S. Bhat