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 DF862C761AF for ; Mon, 3 Apr 2023 14:42:08 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pjLN9-0001LF-Eh; Mon, 03 Apr 2023 10:41:27 -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 1pjLN8-0001L6-8W for qemu-devel@nongnu.org; Mon, 03 Apr 2023 10:41:26 -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 1pjLN6-0000Ey-Bw for qemu-devel@nongnu.org; Mon, 03 Apr 2023 10:41:26 -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 DB92E21E09; Mon, 3 Apr 2023 14:41:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1680532881; 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=zvmpSRbYqVm/pFxZ04J3g3ft05Ip+L0bQ85+8lXUMqY=; b=iXylfkO9D/GDVQXpZACzHtyPR3KPYBtrIRrC9IWbYMz9bb31P8p1aOQF82u9DAKOj3PJ62 Ic2VLjWoecsanU8ARp5wjx16rP08Ehg0C89dc1XyS1A495gEPVtkFHPVujh62WPmtdqI3O +rmodnQ88OUzaZSFyT+2W7PHXyVvCVY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1680532881; 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=zvmpSRbYqVm/pFxZ04J3g3ft05Ip+L0bQ85+8lXUMqY=; b=NVNlflGDV9DtcJuVO0wIvC2gVn2BHjOX/972SdmLwKbNEN1I2s7/ugKsbTXCLywFEM3Z1j XqAe60aoMXw2aqCg== 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 655651331A; Mon, 3 Apr 2023 14:41:21 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id Tw5HC5HlKmRmIAAAMHmgww (envelope-from ); Mon, 03 Apr 2023 14:41:21 +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: <733d9f6b-476c-a401-bc0b-e01fd2206a2a@redhat.com> References: <20230330180336.2791-1-farosas@suse.de> <733d9f6b-476c-a401-bc0b-e01fd2206a2a@redhat.com> Date: Mon, 03 Apr 2023 11:41:18 -0300 Message-ID: <87355hf2pd.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 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 ? > 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.