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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 18421C79FA0 for ; Mon, 7 Sep 2026 14:31:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=d6BAHzKGk625VaU0VDbi12RwRs6cH60WZt4A22q/m/k=; b=f+5U9MNFmv9CLIJNwUOKatc3kP 5CI+SnHzN/2JIxkpscAlRLd+C7TTZ2s68hpg+Cwi1cgnag1J27Xz5nTw8wC18iNfkZhxI0uHK2mu6 S4dsfR8m4aGOtFERTtIkXLOgfbKbpdawsGcEobiHmniLNTCKeUuj8fOUBczeoFRenVaqQDTvIuWBp 5AIV8GbNXyOLkDy75IDrWG7E8OedFjfrRQdfUYXLxJwzXlw9Ep7UHVO4f2VRXu/3T0G/jSq3CNe0F h1rR9uWNKkkbWS83fJPL1DARRwEfBr45Hc7CSuDvNKfHSu82RIcpmsfJgjt6iqInZ7U9KRYYknm3K 9w5RyGTA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x3aNq-000000073N7-1HXI; Mon, 07 Sep 2026 14:31:42 +0000 Received: from smtp-out1.suse.de ([2a07:de40:b251:101:10:150:64:1]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x3aNo-000000073LX-1OpC for linux-nvme@lists.infradead.org; Mon, 07 Sep 2026 14:31:41 +0000 Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 322A52196E; Mon, 7 Sep 2026 14:31:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1788791492; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d6BAHzKGk625VaU0VDbi12RwRs6cH60WZt4A22q/m/k=; b=PHdIYf96dLO5TQEu5MxjRI9GS9XXk3s887DtiqMfDnM+M7kMk+Ihuf/M4wF0uf2DBW642G e48+iFCbNK7e6OQ7DRxfWfZZepU+NjuAthtvk9fYa5RMLn+8C91iK5GVEJcpmSajXcblZv eh7gAfkHp4rIxTLYhYFj5lgPQOJbWPE= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1788791492; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d6BAHzKGk625VaU0VDbi12RwRs6cH60WZt4A22q/m/k=; b=hvyg17em8UXFun3T/GY0dm6Xna9J6qz9bGHEiOYaJqJov1sU7joCPuX5P0TBm8QqFWRjAu Ofr4x6KtXzpLHQBw== Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=mTxj7yq0; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=0fShp0NU DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1788791488; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d6BAHzKGk625VaU0VDbi12RwRs6cH60WZt4A22q/m/k=; b=mTxj7yq0uH8Yo3J0jhrSiI3tys2b2xBBC2Dcqzo1u9/ICD1ZP77pGH6wwcqVhhYwTTcozO 3uBDYT3hCtUTzvgFeJeNlwuCKEnECxCAjKOMm72t60Q1VgB283WilBgYtB4mBFfmx+0HOy 8HXs+GKIaV9IKIbs3GSXCQX+knQnnH8= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1788791488; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d6BAHzKGk625VaU0VDbi12RwRs6cH60WZt4A22q/m/k=; b=0fShp0NUXYSWt0TcmEx474mkrEd1D582YiLquJDuvV2OA2ksxAeIUE0PgFLv3N2bZ6N9xE LLEV+jDeDqIVS8Bw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id B7E0D1339B; Mon, 7 Sep 2026 14:31:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id QIbgK7/KnmpPKgAAD6G6ig (envelope-from ); Mon, 07 Sep 2026 14:31:27 +0000 Message-ID: Date: Mon, 7 Sep 2026 16:31:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 00/10] nvme-multipath: introduce latency I/O policy To: Nilay Shroff , Sagi Grimberg , linux-nvme@lists.infradead.org Cc: kbusch@kernel.org, hch@lst.de, dwagner@suse.de, kanie@linux.alibaba.com, jmeneghi@redhat.com, randyj@purestorage.com, martin.petersen@oracle.com, john.g.garry@oracle.com, gjoyce@linux.ibm.com References: <20260815173502.1185929-1-nilay@linux.ibm.com> <8ecbc5aa-0a5d-4780-9c34-bf433f5e6221@linux.ibm.com> <2a03f032-3fed-454c-a960-ac332b4c3fed@grimberg.me> <77d16701-c829-4fd7-bc4f-8fb51138d9d6@linux.ibm.com> Content-Language: en-US From: Hannes Reinecke In-Reply-To: <77d16701-c829-4fd7-bc4f-8fb51138d9d6@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 322A52196E X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; RCPT_COUNT_TWELVE(0.00)[12]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email,suse.de:mid,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260907_073140_516605_59811DB6 X-CRM114-Status: GOOD ( 15.43 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 8/31/26 8:31 AM, Nilay Shroff wrote: > On 8/31/26 3:23 AM, Sagi Grimberg wrote: >> >> [ .. ]>> I would like to avoid introducing this as a config knob if it is >> always behaves better. >> >> What do others think? > > Good point, however my view is that we may not want to immediately > deprecate or remove queue-depth/round-robin. Based on my testing so > far, across a variety of workloads, including intermittent packet > loss, the latency policy has performed better than queue-depth and > round-robin. However, I would like to see it evaluated against a > broader set of workloads and scenarios, including cases that I > may not have considered/known. > > Once we have broader evidence and establish that latency consistently > performs at least as well as queue-depth/round-robin without any > significant downside, then I think it would be reasonable to consider > deprecating those policies and keeping only numa|latency.> > Until then, I would prefer to keep queue-depth and round-robin as > baseline policies against which we can compare the latency policy. > > But let's wait and see what others think. > I think that we can deprecate round-robin now that we have queue-depth and latency. But I also think that we need both, queue-depth _and_ latency as both latch on different properties, and there are use-cases where one might have workloads which prefer one or the other. Having a config option to select the default (and possibly disable some I/O schedulers) would be completely fine with me, too. Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich