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 46957C433EF for ; Mon, 23 May 2022 16:07:51 +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=yrsenOxrXy9nMdACylnr+sX53uxoGGENf9+HOtweCr8=; b=M0fXjhL2QGjM4UEgHHkf//UKZZ jnJ65iifpaB1+d9UXQL/cNxV6w+7i5LPcv4orHcSKoC30Auk6/rflYqdkTY7z/tJi1+WOiqeLqaQc CzO28HxMm7wNY8abAlHP5Kj9kElE2HZXahu5USHpyrGytCB4wXvCrK1FixYjeKMEcWlfT53m/mzCW YI2LZwIA5vC2PHeY78cl1PtDeXeu1yWJDrCuGHoqN/NNQARh0P+9pzEwYF95G4NLf7vFade22oo7n +dSpx+11kgTVvBJKATrYnSTd2kzaA7mpPexNZEk1ERAPLKBwQ3Rn7CjUhNYdBjgh+L1YkC5JX/QY6 Rw062pTw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1ntAav-0057xm-8T; Mon, 23 May 2022 16:07:45 +0000 Received: from smtp-out1.suse.de ([195.135.220.28]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ntAas-0057wU-PR for linux-nvme@lists.infradead.org; Mon, 23 May 2022 16:07:44 +0000 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 CD4CB21AE4; Mon, 23 May 2022 16:07:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1653322058; 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=yrsenOxrXy9nMdACylnr+sX53uxoGGENf9+HOtweCr8=; b=u7xwGUeq7iG+BzzshlnNDbaFRvqhK1lzfl6RuelwLIqEIuEfaXzjCbPIxYKEdVrAZ9HgzQ 72sYm/5MxW1w6qh2KDNT67Q0n4g+CkrtGd/FZqZPyFckcdmx4vmNx3ud3CQQI5xUnsoE67 zJHVgywcl5eLyM1htshr9/KdPeDh+sY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1653322058; 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=yrsenOxrXy9nMdACylnr+sX53uxoGGENf9+HOtweCr8=; b=TZLN498Bfxpb3cgdAnAaCahoRJZLpgNscK2pmK4Orqwm4h5rzHTBoLRDOcyD6cqNMXpqi9 OlU6O+O+1XapMkCQ== 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 D6999139F5; Mon, 23 May 2022 16:07:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id zxh5Mkmxi2L3KAAAMHmgww (envelope-from ); Mon, 23 May 2022 16:07:37 +0000 Message-ID: <919bfaa2-a35d-052a-1d35-9fdd8faa0d3f@suse.de> Date: Mon, 23 May 2022 18:07:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH 1/3] nvme-tcp: spurious I/O timeout under high load Content-Language: en-US To: Sagi Grimberg , Christoph Hellwig Cc: Keith Busch , linux-nvme@lists.infradead.org References: <20220519062617.39715-1-hare@suse.de> <20220519062617.39715-2-hare@suse.de> <7827d599-7714-3947-ee24-e343e90eee6e@grimberg.me> <96a3315f-43a4-efe6-1f37-0552d66dbd85@suse.de> <96722b37-f943-c3e4-ee6a-440f65e8afca@grimberg.me> <7ec792e3-5110-2272-b6fe-1a976c8c054f@grimberg.me> From: Hannes Reinecke In-Reply-To: <7ec792e3-5110-2272-b6fe-1a976c8c054f@grimberg.me> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220523_090743_015169_F80107A3 X-CRM114-Status: GOOD ( 21.57 ) 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 5/23/22 17:05, Sagi Grimberg wrote: > [ .. ] >>>> I'm open to discussion what we should be doing when the request is >>>> in the process of being sent. But when it didn't have a chance to be >>>> sent and we just overloaded our internal queuing we shouldn't be >>>> sending timeouts. >>> >>> As mentioned above, what happens if that same reporter opens another bug >>> that the same phenomenon happens with soft-iwarp? What would you tell >>> him/her? >> >> Nope. It's a HW appliance. Not a chance to change that. > > It was just a theoretical question. > > Do note that I'm not against solving a problem for anyone, I'm just > questioning if increasing the io_timeout to be unbound in case the > network is congested, is the right solution for everyone instead of > a particular case that can easily be solved with udev to make the > io_timeout to be as high as needed. > > One can argue that this patchset is making nvme-tcp to basically > ignore the device io_timeout in certain cases. Oh, yes, sure, that will happen. What I'm actually arguing is the imprecise difference between BLK_STS_AGAIN / BLK_STS_RESOURCE as a return value from ->queue_rq() and command timeouts in case of resource constraints on the driver implementing ->queue_rq(). If there is a resource constrain driver is free to return BLK_STS_RESOURCE (in which case you wouldn't see a timeout) or accept the request (in which case there will be a timeout). I could live with a timeout if that would just result in the command being retried. But in the case of nvme it results in a connection reset to boot, making customers really nervous that their system is broken. And having a workload which can generate connection resets feels like a DoS attack to me; applications shouldn't be able to do that. Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Ivo Totev, Andrew Myers, Andrew McDonald, Martje Boudien Moerman