From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [RFC PATCH 1/2] KVM: count the number of dirty bits for each memslot Date: Thu, 18 Nov 2010 14:10:20 +0100 Message-ID: <4CE525BC.7020906@siemens.com> References: <20101118141232.d1d25679.yoshikawa.takuya@oss.ntt.co.jp> <20101118141407.265ec727.yoshikawa.takuya@oss.ntt.co.jp> <4CE521FF.5010509@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Takuya Yoshikawa , mtosatti@redhat.com, laijs@cn.fujitsu.com, kvm@vger.kernel.org, takuya.yoshikawa@gmail.com To: Avi Kivity Return-path: Received: from goliath.siemens.de ([192.35.17.28]:18115 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754101Ab0KRNKy (ORCPT ); Thu, 18 Nov 2010 08:10:54 -0500 In-Reply-To: <4CE521FF.5010509@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Am 18.11.2010 13:54, Avi Kivity wrote: > On 11/18/2010 07:14 AM, Takuya Yoshikawa wrote: >> This patch introduces the counter to hold the number of dirty bits in >> each >> memslot. We will use this to optimize dirty logging later. >> >> >> @@ -3217,11 +3216,8 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm, >> >> n = kvm_dirty_bitmap_bytes(memslot); >> >> - for (i = 0; !is_dirty&& i< n/sizeof(long); i++) >> - is_dirty = memslot->dirty_bitmap[i]; >> - > > This can already be an improvement. /Me wonders if it wouldn't make sense to expand this optimization to the user space interface as well, i.e. signaling "there are no dirty pages" via some flag instead of writing zeros in a bitmap. Of course, this means supporting both interfaces for a longer period. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux