From patchwork Thu Nov 26 15:17:28 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrey Gruzdev X-Patchwork-Id: 11934223 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4B0BC56202 for ; Thu, 26 Nov 2020 15:20:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3658E21D40 for ; Thu, 26 Nov 2020 15:20:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3658E21D40 Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=nongnu.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:32824 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kiJ4i-0005bT-Rm for qemu-devel@archiver.kernel.org; Thu, 26 Nov 2020 10:20:48 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47476) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kiJ2B-0003oU-76 for qemu-devel@nongnu.org; Thu, 26 Nov 2020 10:18:11 -0500 Received: from relay.sw.ru ([185.231.240.75]:49550 helo=relay3.sw.ru) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kiJ28-000831-4f for qemu-devel@nongnu.org; Thu, 26 Nov 2020 10:18:10 -0500 Received: from [192.168.15.178] (helo=andrey-MS-7B54.sw.ru) by relay3.sw.ru with esmtp (Exim 4.94) (envelope-from ) id 1kiJ1a-00AT4g-JY; Thu, 26 Nov 2020 18:17:34 +0300 To: qemu-devel@nongnu.org Cc: Den Lunev , Eric Blake , Paolo Bonzini , Juan Quintela , "Dr . David Alan Gilbert" , Markus Armbruster , Peter Xu , Andrey Gruzdev Subject: [PATCH v4 0/6] UFFD write-tracking migration/snapshots Date: Thu, 26 Nov 2020 18:17:28 +0300 Message-Id: <20201126151734.743849-1-andrey.gruzdev@virtuozzo.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Received-SPF: pass client-ip=185.231.240.75; envelope-from=andrey.gruzdev@virtuozzo.com; helo=relay3.sw.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Reply-to: Andrey Gruzdev X-Patchwork-Original-From: Andrey Gruzdev via From: Andrey Gruzdev This patch series is a kind of 'rethinking' of Denis Plotnikov's ideas he's implemented in his series '[PATCH v0 0/4] migration: add background snapshot'. Currently the only way to make (external) live VM snapshot is using existing dirty page logging migration mechanism. The main problem is that it tends to produce a lot of page duplicates while running VM goes on updating already saved pages. That leads to the fact that vmstate image size is commonly several times bigger then non-zero part of virtual machine's RSS. Time required to converge RAM migration and the size of snapshot image severely depend on the guest memory write rate, sometimes resulting in unacceptably long snapshot creation time and huge image size. This series propose a way to solve the aforementioned problems. This is done by using different RAM migration mechanism based on UFFD write protection management introduced in v5.7 kernel. The migration strategy is to 'freeze' guest RAM content using write-protection and iteratively release protection for memory ranges that have already been saved to the migration stream. At the same time we read in pending UFFD write fault events and save those pages out-of-order with higher priority. How to use: 1. Enable write-tracking migration capability virsh qemu-monitor-command --hmp migrate_set_capability. track-writes-ram on 2. Start the external migration to a file virsh qemu-monitor-command --hmp migrate exec:'cat > ./vm_state' 3. Wait for the migration finish and check that the migration has completed. state. Changes v3->v4: * 1. Renamed migrate capability 'track-writes-ram'->'background-snapshot'. * 2. Use array of incompatible caps to replace bulky 'if' constructs. * 3. Moved UFFD low-level code to the separate module ('util/userfaultfd.c'). * 4. Always do UFFD wr-unprotect on cleanup; just closing file descriptor * won't cleanup PTEs anyhow, it will release registration ranges, wait * queues etc. but won't cleanup process MM context on MMU level. * 5. Allow to enable 'background-snapshot' capability on Linux-only hosts. * 6. Put UFFD code usage under '#ifdef CONFIG_LINUX' prerequisite. * 7. Removed 'wt_' from RAMState struct. * 8. Refactored ram_find_and_save_block() to make more clean - poll UFFD * wr-fault events in get_queued_page(), use ram_save_host_page_pre(), * ram_save_host_page_post() notifiers around ram_save_host_page() * instead of bulky inline write-unprotect code. Andrey Gruzdev (6): introduce 'background-snapshot' migration capability introduce UFFD-WP low-level interface helpers support UFFD write fault processing in ram_save_iterate() implementation of background snapshot thread the rest of write tracking migration code introduce simple linear scan rate limiting mechanism include/exec/memory.h | 7 + include/qemu/userfaultfd.h | 29 ++++ migration/migration.c | 314 +++++++++++++++++++++++++++++++++- migration/migration.h | 4 + migration/ram.c | 334 ++++++++++++++++++++++++++++++++++++- migration/ram.h | 4 + migration/savevm.c | 1 - migration/savevm.h | 2 + qapi/migration.json | 7 +- util/meson.build | 1 + util/userfaultfd.c | 215 ++++++++++++++++++++++++ 11 files changed, 908 insertions(+), 10 deletions(-) create mode 100644 include/qemu/userfaultfd.h create mode 100644 util/userfaultfd.c