From patchwork Thu Jan 17 13:55:27 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhuang Yanying X-Patchwork-Id: 10768285 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E3D1113B4 for ; Thu, 17 Jan 2019 14:00:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D38162FF7C for ; Thu, 17 Jan 2019 14:00:36 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C77A82FF83; Thu, 17 Jan 2019 14:00:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 99D722FF7C for ; Thu, 17 Jan 2019 14:00:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727383AbfAQOAe (ORCPT ); Thu, 17 Jan 2019 09:00:34 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:35434 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727291AbfAQOAd (ORCPT ); Thu, 17 Jan 2019 09:00:33 -0500 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 750C448271B1137AD108; Thu, 17 Jan 2019 22:00:30 +0800 (CST) Received: from localhost (10.177.21.2) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.408.0; Thu, 17 Jan 2019 22:00:22 +0800 From: Zhuangyanying To: , , CC: , , , , Zhuang Yanying Subject: [PATCH 0/4] KVM: MMU: fast cleanup D bit based on fast write protect Date: Thu, 17 Jan 2019 13:55:27 +0000 Message-ID: <1547733331-16140-1-git-send-email-ann.zhuangyanying@huawei.com> X-Mailer: git-send-email 2.6.4.windows.1 MIME-Version: 1.0 X-Originating-IP: [10.177.21.2] X-CFilter-Loop: Reflected Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Zhuang Yanying Recently I tested live-migration with large-memory guests, find vcpu may hang for a long time while starting migration, such as 9s for 2048G(linux-5.0.0-rc2+qemu-3.1.0). The reason is memory_global_dirty_log_start() taking too long, and the vcpu is waiting for BQL. The page-by-page D bit clearup is the main time consumption. I think that the idea of "KVM: MMU: fast write protect" by xiaoguangrong, especially the function kvm_mmu_write_protect_all_pages(), is very helpful. After a little modifcation, on his patch, can solve this problem, 9s to 0.5s. At the begining of live migration, write protection is only applied to the top-level SPTE. Then the write from vm trigger the EPT violation, with for_each_shadow_entry write protection is performed at dirct_map. Finally the Dirty bit of the target page(at level 1 page table) is cleared, and the dirty page tracking is started. Of coure, the page where GPA is located is marked dirty when mmu_set_spte. A similar implementation on xen, just emt instead of write protection. What do you think about this solution? Xiao Guangrong (3): KVM: MMU: correct the behavior of mmu_spte_update_no_track KVM: MMU: introduce possible_writable_spte_bitmap KVM: MMU: introduce kvm_mmu_write_protect_all_pages Zhuang Yanying (1): KVM: MMU: fast cleanup D bit based on fast write protect arch/x86/include/asm/kvm_host.h | 25 +++- arch/x86/kvm/mmu.c | 259 ++++++++++++++++++++++++++++++++++++++-- arch/x86/kvm/mmu.h | 1 + arch/x86/kvm/paging_tmpl.h | 13 +- arch/x86/kvm/vmx/vmx.c | 3 +- 5 files changed, 286 insertions(+), 15 deletions(-)