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 77CFDC76196 for ; Fri, 31 Mar 2023 14:39:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1piFtK-0004FX-6l; Fri, 31 Mar 2023 10:38:10 -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 1piFtH-0004F1-Ha for qemu-devel@nongnu.org; Fri, 31 Mar 2023 10:38:07 -0400 Received: from smtp-out1.suse.de ([2001:67c:2178:6::1c]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1piFtF-0006qC-Dw for qemu-devel@nongnu.org; Fri, 31 Mar 2023 10:38:07 -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 A1BC821A5F; Fri, 31 Mar 2023 14:37:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1680273473; 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=snY7drbdjkmlgf0pWIS/7rxdCTggmV1lfkruO1K+rcc=; b=B4jOtp1cQdM2m9pcty6ysbWg4uang3gTiVNcBjWRpeTLKnI1ec9vtpA7QtWXLkn7ltbukR W5NKqRiYfB4WYIFeQcHPjxnOpN2Dlqv9mUdraqrMTHTsUuNkirNquoIdfY//fUfoEHtjvv ahulsC++zQE967Pn051sL47lr0vfyx4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1680273473; 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=snY7drbdjkmlgf0pWIS/7rxdCTggmV1lfkruO1K+rcc=; b=d3pIIFpt1k4veRI0/YAZlhX54bcVjgRUsBSCW4CoZG2rZJ7NBl6RpCVAN2StNL4LCKZLCq i+BW4iCxa1ZGglCw== 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 2311F134F7; Fri, 31 Mar 2023 14:37:52 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id VxJUNkDwJmQEbgAAMHmgww (envelope-from ); Fri, 31 Mar 2023 14:37:52 +0000 From: Fabiano Rosas To: Peter Xu Cc: qemu-devel@nongnu.org, Claudio Fontana , jfehlig@suse.com, dfaggioli@suse.com, dgilbert@redhat.com, =?utf-8?Q?Dani?= =?utf-8?Q?el_P_=2E_Berrang=C3=A9?= , Juan Quintela Subject: Re: [RFC PATCH v1 00/26] migration: File based migration with multifd and fixed-ram In-Reply-To: References: <20230330180336.2791-1-farosas@suse.de> Date: Fri, 31 Mar 2023 11:37:50 -0300 Message-ID: <87edp5oukh.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=2001:67c:2178:6::1c; 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 Peter Xu writes: > On Thu, Mar 30, 2023 at 03:03:10PM -0300, Fabiano Rosas wrote: >> Hi folks, > > Hi, > >> >> 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 > > Have you considered enabling the new fixed-ram format with postcopy when > loading? > > Due to the linear offseting of pages, I think it can achieve super fast vm > loads due to O(1) lookup of pages and local page fault resolutions. > I don't think we have looked that much at the loading side yet. Good to know that it has potential to be faster. I'll look into it. Thanks for the suggestion. >> >> --> new in this series: >> >> 3) MultiFD support: This is about making use of the parallelism >> allowed by the new format. We just need the threading and page >> queuing infrastructure that is already in place for >> multifd. Patches 14-24 implement this; >> >> (qemu) migrate_set_capability fixed-ram on >> (qemu) migrate_set_capability multifd on >> (qemu) migrate_set_parameter multifd-channels 4 >> (qemu) migrate_set_parameter max-bandwith 0 >> (qemu) migrate[_incoming] file:mig >> >> 4) Add a new "direct_io" parameter and enable O_DIRECT for the >> properly aligned segments of the migration (mostly ram). Patch 25. >> >> (qemu) migrate_set_parameter direct-io on >> >> Thanks! Some data below: >> ===== >> >> Outgoing migration to file. NVMe disk. XFS filesystem. >> >> - Single migration runs of stopped 32G guest with ~90% RAM usage. Guest >> running `stress-ng --vm 4 --vm-bytes 90% --vm-method all --verify -t >> 10m -v`: >> >> migration type | MB/s | pages/s | ms >> ----------------+------+---------+------ >> savevm io_uring | 434 | 102294 | 71473 > > So I assume this is the non-live migration scenario. Could you explain > what does io_uring mean here? > This table is all non-live migration. This particular line is a snapshot (hmp_savevm->save_snapshot). I thought it could be relevant because it is another way by which we write RAM into disk. The io_uring is noise, I was initially under the impression that the block device aio configuration affected this scenario. >> file: | 3017 | 855862 | 10301 >> fixed-ram | 1982 | 330686 | 15637 >> ----------------+------+---------+------ >> fixed-ram + multifd + O_DIRECT >> 2 ch. | 5565 | 1500882 | 5576 >> 4 ch. | 5735 | 1991549 | 5412 >> 8 ch. | 5650 | 1769650 | 5489 >> 16 ch. | 6071 | 1832407 | 5114 >> 32 ch. | 6147 | 1809588 | 5050 >> 64 ch. | 6344 | 1841728 | 4895 >> 128 ch. | 6120 | 1915669 | 5085 >> ----------------+------+---------+------ > > Thanks,