From patchwork Thu Jan 21 15:02:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Zhijian Li (Fujitsu)\" via" X-Patchwork-Id: 12036535 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,URIBL_BLOCKED,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 B20DCC433DB for ; Thu, 21 Jan 2021 15:04:48 +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 43631238E3 for ; Thu, 21 Jan 2021 15:04:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 43631238E3 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]:35458 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l2bVv-0001K2-Bj for qemu-devel@archiver.kernel.org; Thu, 21 Jan 2021 10:04:47 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:45764) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2bUD-0008Pv-2J for qemu-devel@nongnu.org; Thu, 21 Jan 2021 10:03:01 -0500 Received: from relay.sw.ru ([185.231.240.75]:43268) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2bU3-0003ZA-SC for qemu-devel@nongnu.org; Thu, 21 Jan 2021 10:03:00 -0500 Received: from [192.168.15.91] (helo=andrey-MS-7B54.sw.ru) by relay.sw.ru with esmtp (Exim 4.94) (envelope-from ) id 1l2bTl-0004cV-Uo; Thu, 21 Jan 2021 18:02:33 +0300 To: qemu-devel@nongnu.org Subject: [PATCH v12 0/5] UFFD write-tracking migration/snapshots Date: Thu, 21 Jan 2021 18:02:29 +0300 Message-Id: <20210121150234.192543-1-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=relay.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: , Cc: Juan Quintela , "Dr . David Alan Gilbert" , Peter Xu , Markus Armbruster , Paolo Bonzini , Den Lunev , Andrey Gruzdev 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: "Zhijian Li (Fujitsu)\" via" 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 background-snapshot 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 v11->v12: * 1. Consolidated UFFD-related code under single #if defined(__linux__). * 2. Abandoned use of pre/post hooks in ram_find_and_save_block() in favour * of more compact code fragment in ram_save_host_page(). * 3. Refactored/simplified eBPF code in userfaultfd-wrlat.py script. Changes v10->v11: * 1. Updated commit messages. Changes v9->v10: * 1. Fixed commit message for [PATCH v9 1/5]. Changes v8->v9: * 1. Fixed wrong cover letter subject. Changes v7->v8: * 1. Fixed coding style problems to pass checkpatch. Changes v6->v7: * 1. Fixed background snapshot on suspended guest: call qemu_system_wakeup_request() * before stopping VM to make runstate transition valid. * 2. Disabled dirty page logging and log syn when 'background-snapshot' is enabled. * 3. Introduced 'userfaultfd-wrlat.py' script to analyze UFFD write fault latencies. Changes v5->v6: * 1. Consider possible hot pluggin/unpluggin of memory device - don't use static * for write-tracking support level in migrate_query_write_tracking(), check * each time when one tries to enable 'background-snapshot' capability. Changes v4->v5: * 1. Refactored util/userfaultfd.c code to support features required by postcopy. * 2. Introduced checks for host kernel and guest memory backend compatibility * to 'background-snapshot' branch in migrate_caps_check(). * 3. Switched to using trace_xxx instead of info_report()/error_report() for * cases when error message must be hidden (probing UFFD-IO) or info may be * really littering output if goes to stderr. * 4 Added RCU_READ_LOCK_GUARDs to the code dealing with RAM block list. * 5. Added memory_region_ref() for each RAM block being wr-protected. * 6. Reused qemu_ram_block_from_host() instead of custom RAM block lookup routine. * 7. Refused from using specific hwaddr/ram_addr_t in favour of void */uint64_t. * 8. Currently dropped 'linear-scan-rate-limiting' patch. The reason is that * that choosen criteria for high-latency fault detection (i.e. timestamp of * UFFD event fetch) is not representative enough for this task. * At the moment it looks somehow like premature optimization effort. * 8. Dropped some unnecessary/unused code. Andrey Gruzdev (5): migration: introduce 'background-snapshot' migration capability migration: introduce UFFD-WP low-level interface helpers migration: support UFFD write fault processing in ram_save_iterate() migration: implementation of background snapshot thread migration: introduce 'userfaultfd-wrlat.py' script include/exec/memory.h | 8 + include/qemu/userfaultfd.h | 35 ++++ migration/migration.c | 357 ++++++++++++++++++++++++++++++++++- migration/migration.h | 4 + migration/ram.c | 303 ++++++++++++++++++++++++++++- migration/ram.h | 6 + migration/savevm.c | 1 - migration/savevm.h | 2 + migration/trace-events | 2 + qapi/migration.json | 7 +- scripts/userfaultfd-wrlat.py | 122 ++++++++++++ util/meson.build | 1 + util/trace-events | 9 + util/userfaultfd.c | 345 +++++++++++++++++++++++++++++++++ 14 files changed, 1190 insertions(+), 12 deletions(-) create mode 100644 include/qemu/userfaultfd.h create mode 100755 scripts/userfaultfd-wrlat.py create mode 100644 util/userfaultfd.c