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 EEC54C76196 for ; Mon, 3 Apr 2023 16:36:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pjNAG-0000Py-3e; Mon, 03 Apr 2023 12:36:16 -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 1pjNAE-0000Pi-Hg for qemu-devel@nongnu.org; Mon, 03 Apr 2023 12:36:14 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pjNAB-0001XN-RK for qemu-devel@nongnu.org; Mon, 03 Apr 2023 12:36:14 -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-out1.suse.de (Postfix) with ESMTPS id E421A21EFB; Mon, 3 Apr 2023 16:36:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1680539766; 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=2pAgJFGvuJ+P940PQwh4Z+u94QU2XqpVkuRyLRR6ZHg=; b=LhHJTtVrxQGAmrqVL3UpuNpgZbdw21L2IWY030LaoteCDkj9s3dhfB25wBu2BOd+XDmttb 6OfFECdhi0nANZdF+ZJUmM4bdOBA5j1DYRW1T34qavIUDZRNLrWtTbdmZktibbkDHhOjUS UGkGetSBOYW50JafndcrWpudxE4Tenc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1680539766; 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=2pAgJFGvuJ+P940PQwh4Z+u94QU2XqpVkuRyLRR6ZHg=; b=rXrl9xEL65EOQvb0PGVKLEbyhPcPvGj1gXad17xWeW3scURtaJQrSq4SCEZll7ts0+bnSH aqSzCGzNX4gN8mDQ== 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 6E95013416; Mon, 3 Apr 2023 16:36:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 50qgDXYAK2QjYwAAMHmgww (envelope-from ); Mon, 03 Apr 2023 16:36:06 +0000 From: Fabiano Rosas To: David Hildenbrand , qemu-devel@nongnu.org Cc: Claudio Fontana , jfehlig@suse.com, dfaggioli@suse.com, dgilbert@redhat.com, =?utf-8?Q?Daniel_P_=2E_Berrang?= =?utf-8?Q?=C3=A9?= , Juan Quintela Subject: Re: [RFC PATCH v1 00/26] migration: File based migration with multifd and fixed-ram In-Reply-To: <39fb1702-1db3-4525-24f1-5f4f506a6d0b@redhat.com> References: <20230330180336.2791-1-farosas@suse.de> <733d9f6b-476c-a401-bc0b-e01fd2206a2a@redhat.com> <87355hf2pd.fsf@suse.de> <39fb1702-1db3-4525-24f1-5f4f506a6d0b@redhat.com> Date: Mon, 03 Apr 2023 13:36:03 -0300 Message-ID: <87v8icexe4.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=195.135.220.28; envelope-from=farosas@suse.de; helo=smtp-out1.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 David Hildenbrand writes: > On 03.04.23 16:41, Fabiano Rosas wrote: >> David Hildenbrand writes: >> >>> On 30.03.23 20:03, Fabiano Rosas wrote: >>>> Hi folks, >>>> >>>> I'm continuing the work done last year to add a new format of >>>> migration stream that can be used to migrate large guests to a single >>>> file in a performant way. >>>> >>>> This is an early RFC with the previous code + my additions to support >>>> multifd and direct IO. Let me know what you think! >>>> >>>> Here are the reference links for previous discussions: >>>> >>>> https://lists.gnu.org/archive/html/qemu-devel/2022-08/msg01813.html >>>> https://lists.gnu.org/archive/html/qemu-devel/2022-10/msg01338.html >>>> https://lists.gnu.org/archive/html/qemu-devel/2022-10/msg05536.html >>>> >>>> The series has 4 main parts: >>>> >>>> 1) File migration: A new "file:" migration URI. So "file:mig" does the >>>> same as "exec:cat > mig". Patches 1-4 implement this; >>>> >>>> 2) Fixed-ram format: A new format for the migration stream. Puts guest >>>> pages at their relative offsets in the migration file. This saves >>>> space on the worst case of RAM utilization because every page has a >>>> fixed offset in the migration file and (potentially) saves us time >>>> because we could write pages independently in parallel. It also >>>> gives alignment guarantees so we could use O_DIRECT. Patches 5-13 >>>> implement this; >>>> >>>> With patches 1-13 these two^ can be used with: >>>> >>>> (qemu) migrate_set_capability fixed-ram on >>>> (qemu) migrate[_incoming] file:mig >>> >>> There are some use cases (especially virtio-mem, but also virtio-balloon >>> with free-page-hinting) where we end up having very sparse guest RAM. We >>> don't want to have such "memory without meaning" in the migration stream >>> nor restore it on the destination. >>> >> >> Is that what is currently defined by ramblock_page_is_discarded -> >> virtio_mem_rdm_is_populated ? > > For virtio-mem, yes. For virtio-balloon we communicate that information > via qemu_guest_free_page_hint(). > >> >>> Would that still be supported with the new format? For example, have a >>> sparse VM savefile and remember which ranges actually contain reasonable >>> data? >> >> We do ignore zero pages, so I don't think it would be an issue to have >> another criteria for ignoring pages. It seems if we do enable postcopy >> load w/ fixed-ram that would be already handled in postcopy_request_page. > > Ok, good. Just to note that we do have migration of sparse RAM blocks > working and if fixed-ram would be incompatible we'd have to fence it. Yep, thanks for the heads-up. I'll keep that in mind.