Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756212Ab2BALKk (ORCPT ); Wed, 1 Feb 2012 06:10:40 -0500 Received: from serv2.oss.ntt.co.jp ([222.151.198.100]:48658 "EHLO serv2.oss.ntt.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756135Ab2BALKi (ORCPT ); Wed, 1 Feb 2012 06:10:38 -0500 Message-ID: <4F291E1F.3030505@oss.ntt.co.jp> Date: Wed, 01 Feb 2012 20:12:31 +0900 From: Takuya Yoshikawa User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; ja; rv:1.9.2.25) Gecko/20111213 Thunderbird/3.1.17 MIME-Version: 1.0 To: Avi Kivity CC: Peter Zijlstra , paulmck@linux.vnet.ibm.com, Oleg Nesterov , linux-kernel , Marcelo Tosatti , KVM list Subject: Re: [RFC][PATCH] srcu: Implement call_srcu() References: <1328016724.2446.229.camel@twins> <4F27F0E6.1040309@redhat.com> <1328017807.2446.230.camel@twins> <20120131222447.GH2391@linux.vnet.ibm.com> <1328091749.2760.34.camel@laptop> <4F29178A.1090306@redhat.com> <4F2918D5.4050104@redhat.com> <4F291B56.30600@oss.ntt.co.jp> <4F291B92.8070402@redhat.com> In-Reply-To: <4F291B92.8070402@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1177 Lines: 41 (2012/02/01 20:01), Avi Kivity wrote: > On 02/01/2012 01:00 PM, Takuya Yoshikawa wrote: >> How about just doing: >> >> take a spin_lock >> copy the entire (or some portions of) bitmap locally >> clear the bitmap >> unlock >> > > That means that vcpus dirtying memory also have to take that lock, and > spin while the bitmap is being copied. So kvm_vm_ioctl_get_dirty_log() > will become faster, at the expense of vcpus, which I think is a bad > tradeoff. Almost every caller is already holding the mmu_lock. Isn't it possible to make others hold the lock only for the case of marking to the bitmap? (I will check myself too.) >> write protect the dirty pages based on the copied dirty data >> >> copy_to_user >> >> >> >> I can show you some performance numbers, this weekend, if you like. > > That'll be great, numbers are better than speculation. > Yes, I already have some good numbers to show (and some patches). Takuya -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/