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 579C9C07545 for ; Tue, 24 Oct 2023 18:13:16 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qvLtj-00057k-T8; Tue, 24 Oct 2023 14:12:59 -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 1qvLtg-0004tY-71 for qemu-devel@nongnu.org; Tue, 24 Oct 2023 14:12:56 -0400 Received: from smtp-out2.suse.de ([2001:67c:2178:6::1d]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qvLta-0005S8-2L for qemu-devel@nongnu.org; Tue, 24 Oct 2023 14:12:55 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 525101FE9E; Tue, 24 Oct 2023 18:12:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1698171167; h=from:from:reply-to: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=QuFjuBT12MKx7y0Y/HRmjrY+8s+RB52SpTSjoy6KBE4=; b=DFe7W1IDotCiEOP7h6bykh5tVPYJ6TKZ9yCKn6oYrc5ArtKwR04qJAbcEHS/Yrd7oGxsOI nxl4HFKAoPVFsT63KraYZZaIS52lzDSvr6pqqu3qii3w/xufiyrXQmE3IdvD9Ptp9bmgdu if1COUTS61YcS6LR2oFV7zDst4v71NE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1698171167; h=from:from:reply-to: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=QuFjuBT12MKx7y0Y/HRmjrY+8s+RB52SpTSjoy6KBE4=; b=J0JP+0wLJKeFvMI6qC5lgOabgWnRXRAg2O3yZKw+aJNnJS+2nHZAtn8YM+h91yAJg1M9lj EkrEUkRCU+pqHwBQ== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id D78521391C; Tue, 24 Oct 2023 18:12:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id X31bKB4JOGWPHQAAMHmgww (envelope-from ); Tue, 24 Oct 2023 18:12:46 +0000 From: Fabiano Rosas To: Markus Armbruster Cc: qemu-devel@nongnu.org, berrange@redhat.com, Juan Quintela , Peter Xu , Leonardo Bras , Claudio Fontana , Eric Blake Subject: Re: [PATCH v2 06/29] migration: Add auto-pause capability In-Reply-To: <87r0lkvbfd.fsf@pond.sub.org> References: <20231023203608.26370-1-farosas@suse.de> <20231023203608.26370-7-farosas@suse.de> <87r0lkvbfd.fsf@pond.sub.org> Date: Tue, 24 Oct 2023 15:12:44 -0300 Message-ID: <8734xzevoj.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Authentication-Results: smtp-out2.suse.de; none X-Spamd-Result: default: False [-4.10 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; BAYES_HAM(-0.00)[36.35%]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-3.00)[-1.000]; MIME_GOOD(-0.10)[text/plain]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-1.00)[-1.000]; RCPT_COUNT_SEVEN(0.00)[8]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] Received-SPF: pass client-ip=2001:67c:2178:6::1d; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, 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 Markus Armbruster writes: > Fabiano Rosas writes: > >> Add a capability that allows the management layer to delegate to QEMU >> the decision of whether to pause a VM and perform a non-live >> migration. Depending on the type of migration being performed, this >> could bring performance benefits. >> >> Note that the capability is enabled by default but at this moment no >> migration scheme is making use of it. > > This sounds as if the capability has no effect unless the "migration > scheme" (whatever that may be) opts into using it. Am I confused? > What I mean here is that this capability is implemented and functional, but I'm not retroactively enabling any existing migration code to use auto-pause. Otherwise people would start seeing their guests being paused before migraton in scenarios they never used to pause. By "migration scheme" I mean types of migration. Or modes of operation. Or exclusive parameters. Anything that is different enough from what exists today that we would consider a different type of migration. Anything that allow us to break backward compatibility (because it never existed before to begin with). E.g. this series introduces the fixed-ram migration. That never existed before. So from the moment we enable that code to use this capability, it will always do auto-pause, unless the management layer wants to avoid it. >> Signed-off-by: Fabiano Rosas > > [...] > >> diff --git a/qapi/migration.json b/qapi/migration.json >> index db3df12d6c..74f12adc0e 100644 >> --- a/qapi/migration.json >> +++ b/qapi/migration.json >> @@ -523,6 +523,10 @@ >> # and can result in more stable read performance. Requires KVM >> # with accelerator property "dirty-ring-size" set. (Since 8.1) >> # >> +# @auto-pause: If enabled, allows QEMU to decide whether to pause the >> +# VM before migration for an optimal migration performance. >> +# Enabled by default. (since 8.1) > > If this needs an opt-in to take effect, it should be documented. > Someting like this perhaps? # @auto-pause: If enabled, allows QEMU to decide whether to pause the VM # before migration for an optimal migration performance. Enabled by # default. New migration code needs to opt-in at # migration_should_pause(), otherwise this behaves as if # disabled. (since 8.2) >> +# >> # Features: >> # >> # @unstable: Members @x-colo and @x-ignore-shared are experimental. >> @@ -539,7 +543,7 @@ >> { 'name': 'x-ignore-shared', 'features': [ 'unstable' ] }, >> 'validate-uuid', 'background-snapshot', >> 'zero-copy-send', 'postcopy-preempt', 'switchover-ack', >> - 'dirty-limit'] } >> + 'dirty-limit', 'auto-pause'] } >> >> ## >> # @MigrationCapabilityStatus: