From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031126Ab1EXB0x (ORCPT ); Mon, 23 May 2011 21:26:53 -0400 Received: from rcsinet10.oracle.com ([148.87.113.121]:18577 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754976Ab1EXB0u (ORCPT ); Mon, 23 May 2011 21:26:50 -0400 Message-ID: <4DDB093F.2060601@kernel.org> Date: Mon, 23 May 2011 18:26:23 -0700 From: Yinghai Lu User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110414 SUSE/3.1.10 Thunderbird/3.1.10 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, tglx@linutronix.de, mingo@elte.hu Subject: Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based on semi-formal proof" References: <4DD6F64C.3030402@kernel.org> <20110520234923.GQ2366@linux.vnet.ibm.com> <4DD70120.9090801@kernel.org> <20110521131844.GE2271@linux.vnet.ibm.com> <20110521140845.GA12157@linux.vnet.ibm.com> <4DDAC01E.7050602@kernel.org> <20110523212530.GF7428@linux.vnet.ibm.com> <4DDAD934.9010603@kernel.org> <4DDAE5FA.2030303@kernel.org> <4DDAE6A5.6060701@kernel.org> <20110524011824.GL7428@linux.vnet.ibm.com> In-Reply-To: <20110524011824.GL7428@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: acsinet22.oracle.com [141.146.126.238] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090204.4DDB0947.009A,ss=1,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/23/2011 06:18 PM, Paul E. McKenney wrote: > OK, so it looks like I need to get this out of the way in order to track > down the delays. Or does reverting PeterZ's patch get you a stable > system, but with the longish delays in memory_dev_init()? If the latter, > it might be more productive to handle the two problems separately. > > For whatever it is worth, I do see about 5% increase in grace-period > duration when switching to kthreads. This is acceptable -- your > 30x increase clearly is completely unacceptable and must be fixed. > Other than that, the main thing that affects grace period duration is > the setting of CONFIG_HZ -- the smaller the HZ value, the longer the > grace-period duration. for my 1024g system when memory hotadd is enabled in kernel config: 1. current linus tree + tip tree: memory_dev_init will take about 100s. 2. current linus tree + tip tree + your tree - Peterz patch: a. on fedora 14 gcc: will cost about 4s: like old times b. on opensuse 11.3 gcc: will cost about 10s. Thanks Yinghai Lu