From mboxrd@z Thu Jan 1 00:00:00 1970 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=-10.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 D1AE7C433DB for ; Thu, 4 Feb 2021 17:28:27 +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 54CA064DD6 for ; Thu, 4 Feb 2021 17:28:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 54CA064DD6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45452 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7iQc-00009v-AK for qemu-devel@archiver.kernel.org; Thu, 04 Feb 2021 12:28:26 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:44518) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7htE-0008HZ-6U for qemu-devel@nongnu.org; Thu, 04 Feb 2021 11:53:57 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:60397) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7ht9-0002K6-Th for qemu-devel@nongnu.org; Thu, 04 Feb 2021 11:53:55 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612457631; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hP+DR++xu3ptHhHPWxCLN/culkyAHdRwLQCA1dZFR74=; b=MyzH///gUKdzwI9nyFRwapdwT66Lfi29BD6Gn1/MfSA/PNBZDDF9ljhJOUhCddVqSS19cd T0DLjwTx8ihAhzHc5hS5uxLhB+MM0bmGe8IiWhdNIw/iPy3K+Pr6ct/mb4NFO3M7MDnJNU nw83Hvo4pNHd8qBQko7JELVXEbVPLd8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-549-uaPw7mloOaaCeFehgs9M_g-1; Thu, 04 Feb 2021 11:53:49 -0500 X-MC-Unique: uaPw7mloOaaCeFehgs9M_g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 13474100F340; Thu, 4 Feb 2021 16:53:48 +0000 (UTC) Received: from work-vm (ovpn-114-21.ams2.redhat.com [10.36.114.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9BA5F1D5; Thu, 4 Feb 2021 16:53:43 +0000 (UTC) Date: Thu, 4 Feb 2021 16:53:20 +0000 From: "Dr. David Alan Gilbert" To: Andrey Gruzdev Subject: Re: [PATCH v14 0/5] UFFD write-tracking migration/snapshots Message-ID: <20210204165320.GA4276@work-vm> References: <20210129101407.103458-1-andrey.gruzdev@virtuozzo.com> <20210204150140.GC24147@work-vm> MIME-Version: 1.0 In-Reply-To: <20210204150140.GC24147@work-vm> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.351, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 , Markus Armbruster , Peter Xu , qemu-devel@nongnu.org, Paolo Bonzini , Den Lunev Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Dr. David Alan Gilbert (dgilbert@redhat.com) wrote: > * Andrey Gruzdev (andrey.gruzdev@virtuozzo.com) wrote: > > 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. > > Queued > Andrey: I've fixed up some 32bit build casts in the pull. Please check them. Dave > > 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 v13->v14: > > > > * 1. Removed unneeded '#ifdef CONFIG_LINUX' from [PATCH 1/5] where #ifdef'ed > > * code was originally introduced. In v13 removed #ifdef's appeared to be > > * a diff in [PATCH 4/5] on top of previous patches. > > > > Changes v12->v13: > > > > * 1. Fixed codestyle problem for checkpatch. > > > > 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 > > > > -- > > 2.25.1 > > > > > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK