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 22B66C07545 for ; Tue, 24 Oct 2023 05:42:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qvAAS-0004Sg-Hc; Tue, 24 Oct 2023 01:41:28 -0400 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 1qvAAR-0004RX-1i for qemu-devel@nongnu.org; Tue, 24 Oct 2023 01:41:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qvAAP-0002iR-Fs for qemu-devel@nongnu.org; Tue, 24 Oct 2023 01:41:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1698126084; 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=k5DQ+NMoxi5b1s7fhqQ2jpKc/hBEEr4hjOtri/WtV/U=; b=UbcRoY7WTrO5lpwuNuUzIIa3WqC87R0iVjWrZTt5vF40EagFQe/n9h8dLOexek/18rd3k0 cBaL04fVaGZ/XBzQbfMIoN0xTl9FADMeCy+fsPPob4ZZfdc8EVrihKNGhcUUBsv89zUU+q WaDw60Gk9DDFn+WrVvhJJD7kuis7ZaA= 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-482-UY_2TTDMOzO_TAwSZx0aCw-1; Tue, 24 Oct 2023 01:41:20 -0400 X-MC-Unique: UY_2TTDMOzO_TAwSZx0aCw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (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 364A538062A7; Tue, 24 Oct 2023 05:41:20 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.56]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 139E41121318; Tue, 24 Oct 2023 05:41:20 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E778021E6A1F; Tue, 24 Oct 2023 07:41:18 +0200 (CEST) From: Markus Armbruster To: Fabiano Rosas Cc: qemu-devel@nongnu.org, berrange@redhat.com, Juan Quintela , Peter Xu , Leonardo Bras , Claudio Fontana , Eric Blake Subject: Re: [PATCH v2 28/29] migration: Add direct-io parameter References: <20231023203608.26370-1-farosas@suse.de> <20231023203608.26370-29-farosas@suse.de> Date: Tue, 24 Oct 2023 07:41:18 +0200 In-Reply-To: <20231023203608.26370-29-farosas@suse.de> (Fabiano Rosas's message of "Mon, 23 Oct 2023 17:36:07 -0300") Message-ID: <878r7svapt.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_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: 2.1.29 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 the direct-io migration parameter that tells the migration code to > use O_DIRECT when opening the migration stream file whenever possible. > > This is currently only used for the secondary channels of fixed-ram > migration, which can guarantee that writes are page aligned. > > However the parameter could be made to affect other types of > file-based migrations in the future. > > Signed-off-by: Fabiano Rosas When would you want to enable @direct-io, and when would you want to leave it disabled? What happens when you enable @direct-io with a migration that cannot use O_DIRECT? [...] > diff --git a/qapi/migration.json b/qapi/migration.json > index 1317dd32ab..3eb9e2c9b5 100644 > --- a/qapi/migration.json > +++ b/qapi/migration.json > @@ -840,6 +840,9 @@ > # @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration. > # Defaults to 1. (Since 8.1) > # > +# @direct-io: Open migration files with O_DIRECT when possible. Not > +# all migration transports support this. (since 8.1) > +# Please format like # @direct-io: Open migration files with O_DIRECT when possible. Not # all migration transports support this. (since 8.1) to blend in with recent commit a937b6aa739 (qapi: Reformat doc comments to conform to current conventions). > # Features: > # > # @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period > @@ -864,7 +867,7 @@ > 'multifd-zlib-level', 'multifd-zstd-level', > 'block-bitmap-mapping', > { 'name': 'x-vcpu-dirty-limit-period', 'features': ['unstable'] }, > - 'vcpu-dirty-limit'] } > + 'vcpu-dirty-limit', 'direct-io'] } > > ## > # @MigrateSetParameters: > @@ -1016,6 +1019,9 @@ > # @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration. > # Defaults to 1. (Since 8.1) > # > +# @direct-io: Open migration files with O_DIRECT when possible. Not > +# all migration transports support this. (since 8.1) > +# Likewise. > # Features: > # > # @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period > @@ -1058,7 +1064,8 @@ > '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ], > '*x-vcpu-dirty-limit-period': { 'type': 'uint64', > 'features': [ 'unstable' ] }, > - '*vcpu-dirty-limit': 'uint64'} } > + '*vcpu-dirty-limit': 'uint64', > + '*direct-io': 'bool' } } > > ## > # @migrate-set-parameters: > @@ -1230,6 +1237,9 @@ > # @vcpu-dirty-limit: Dirtyrate limit (MB/s) during live migration. > # Defaults to 1. (Since 8.1) > # > +# @direct-io: Open migration files with O_DIRECT when possible. Not > +# all migration transports support this. (since 8.1) > +# Likewise. > # Features: > # > # @unstable: Members @x-checkpoint-delay and @x-vcpu-dirty-limit-period > @@ -1269,7 +1279,8 @@ > '*block-bitmap-mapping': [ 'BitmapMigrationNodeAlias' ], > '*x-vcpu-dirty-limit-period': { 'type': 'uint64', > 'features': [ 'unstable' ] }, > - '*vcpu-dirty-limit': 'uint64'} } > + '*vcpu-dirty-limit': 'uint64', > + '*direct-io': 'bool' } } > > ## > # @query-migrate-parameters: This one is for the migration maintainers: we have MigrationCapability, set with migrate-set-capabilities, and MigrationParameters, set with migrate-set-parameters. For a boolean configuration setting, either works. Which one should we use when? [...]