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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id F3126C5478A for ; Wed, 21 Feb 2024 15:39:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rcoaC-0006ZD-MN; Wed, 21 Feb 2024 10:32:28 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rcoSD-0003Ss-KJ for qemu-devel@nongnu.org; Wed, 21 Feb 2024 10:24:13 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rciAE-00057v-EU for qemu-devel@nongnu.org; Wed, 21 Feb 2024 03:41:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708504872; 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=kQC3iDEwTU0zOMJx2FKCKhfHkf/F88iH7Ne+kunsMtE=; b=gYRXgcX1838su7vEB4yg34v9CeAKHJrJwX0PYgU7ZBNTQSpyIDs0sY7qUm2JXpyI/awBxm OkrhYxnj58kudyPfO0HUCKoHP9pXBHLY1I7loFkNR1lX10r2opMeLYD018NI1DXVz6/w+O 4LCeGOXc13ZVQjuM3R4o8PsiW14PVP0= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-513-V6DZBQODM3KJGgo7izz8WQ-1; Wed, 21 Feb 2024 03:41:10 -0500 X-MC-Unique: V6DZBQODM3KJGgo7izz8WQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0853D1C0BB5B; Wed, 21 Feb 2024 08:41:10 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D9C012166B36; Wed, 21 Feb 2024 08:41:09 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 9C5C821E66D5; Wed, 21 Feb 2024 09:41:08 +0100 (CET) From: Markus Armbruster To: Fabiano Rosas Cc: qemu-devel@nongnu.org, berrange@redhat.com, Peter Xu , Claudio Fontana , Eric Blake Subject: Re: [PATCH v4 11/34] migration/ram: Introduce 'fixed-ram' migration capability In-Reply-To: <20240220224138.24759-12-farosas@suse.de> (Fabiano Rosas's message of "Tue, 20 Feb 2024 19:41:15 -0300") References: <20240220224138.24759-1-farosas@suse.de> <20240220224138.24759-12-farosas@suse.de> Date: Wed, 21 Feb 2024 09:41:08 +0100 Message-ID: <87o7caxl97.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.05, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 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-bounces+qemu-devel=archiver.kernel.org@nongnu.org Fabiano Rosas writes: > Add a new migration capability 'fixed-ram'. > > The core of the feature is to ensure that each RAM page has a specific > offset in the resulting migration stream. The reasons why we'd want > such behavior are: > > - The resulting file will have a bounded size, since pages which are > dirtied multiple times will always go to a fixed location in the > file, rather than constantly being added to a sequential > stream. This eliminates cases where a VM with, say, 1G of RAM can > result in a migration file that's 10s of GBs, provided that the > workload constantly redirties memory. > > - It paves the way to implement O_DIRECT-enabled save/restore of the > migration stream as the pages are ensured to be written at aligned > offsets. > > - It allows the usage of multifd so we can write RAM pages to the > migration file in parallel. > > For now, enabling the capability has no effect. The next couple of > patches implement the core functionality. > > Signed-off-by: Fabiano Rosas [...] > diff --git a/qapi/migration.json b/qapi/migration.json > index 5a565d9b8d..3fce5fe53e 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -531,6 +531,10 @@ > # and can result in more stable read performance. Requires KVM > # with accelerator property "dirty-ring-size" set. (Since 8.1) > # > +# @fixed-ram: Migrate using fixed offsets in the migration file for > +# each RAM page. Requires a migration URI that supports seeking, > +# such as a file. (since 9.0) > +# > # Features: > # > # @deprecated: Member @block is deprecated. Use blockdev-mirror with > @@ -555,7 +559,7 @@ > { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, > 'validate-uuid', 'background-snapshot', > 'zero-copy-send', 'postcopy-preempt', 'switchover-ack', > - 'dirty-limit'] } > + 'dirty-limit', 'fixed-ram'] } > > ## > # @MigrationCapabilityStatus: Can we find a better name than @fixed-ram? @fixed-ram-offsets? @use-seek? Apart from that, QAPI schema Acked-by: Markus Armbruster