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 X-Spam-Level: X-Spam-Status: No, score=-4.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DA5AC433DB for ; Tue, 9 Feb 2021 15:39:08 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EBE4164EB8 for ; Tue, 9 Feb 2021 15:39:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EBE4164EB8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kioxia.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XcmOjDbEgv5NzJd+TiZB7FEKnnvE+uKKy3hUAKwPW7I=; b=p/L/xUhTLdrXyAnT46x91Shz0 Z6C/0T4YdvYAxM7f1SkA6CvwvsPrq6bDAnsVlPZiIF7oILvqpXxVLHULMZx7g5wbmthU2QF1U91wV 38A9GEPbuRmw35e/jQqH6sEZiA6+pMnEsfpBNzYum+yE3GeH0NpYWj/uWO6d9bFGm9GRqYIhm2Uwx l8qlq+WDpznHB3HmA1v0VPWCzhRSvcCPe3LZZPn5nO3HWDTe5cZz4KGnh/vF+WanG5BdFGrhSDUJv h2nwh6qJsuT/1mIAXoXEb2nUVj1TwsLpvZV1BcViknRfwmaoIP6XSx1zoRpomfikhCj71/DIaEbGr Oi9I2f8zQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l9V6T-0001Vx-UE; Tue, 09 Feb 2021 15:39:01 +0000 Received: from usmailhost21.kioxia.com ([12.0.68.226] helo=SJSMAIL01.us.kioxia.com) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l9V6O-0001VF-UC for linux-nvme@lists.infradead.org; Tue, 09 Feb 2021 15:38:59 +0000 Received: from SJSMAIL01.us.kioxia.com (10.90.133.90) by SJSMAIL01.us.kioxia.com (10.90.133.90) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1779.2; Tue, 9 Feb 2021 07:38:53 -0800 Received: from SJSMAIL01.us.kioxia.com ([fe80::98fb:6d15:be65:b22d]) by SJSMAIL01.us.kioxia.com ([fe80::98fb:6d15:be65:b22d%3]) with mapi id 15.01.1779.007; Tue, 9 Feb 2021 07:38:53 -0800 From: Clay Mayers To: Keith Busch Subject: RE: [PATCH V2 0/2] nvme: Support for fused NVME_IOCTL_SUBMIT_IO Thread-Topic: [PATCH V2 0/2] nvme: Support for fused NVME_IOCTL_SUBMIT_IO Thread-Index: AQHW81Uk6e6cbZGyEU2+tznAk87Vf6o6RTXQgBS+TpCAAL7WAIAARTzQ Date: Tue, 9 Feb 2021 15:38:53 +0000 Message-ID: <16731baa6d8f4729a10edeea57267c41@kioxia.com> References: <20210105224939.1336-2-clay.mayers@kioxia.com> <20210125195844.1390581-1-clay.mayers@kioxia.com> <20210209031252.GA97526@C02WT3WMHTD6> In-Reply-To: <20210209031252.GA97526@C02WT3WMHTD6> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.90.53.138] MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210209_103856_992032_141C192C X-CRM114-Status: GOOD ( 24.91 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , Sagi Grimberg , Chaitanya Kulkarni , "linux-nvme@lists.infradead.org" , Christoph Hellwig Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org > From: Keith Busch > Sent: Monday, February 8, 2021 7:13 PM > To: Clay Mayers > Cc: linux-nvme@lists.infradead.org; Jens Axboe ; Chaitanya > Kulkarni ; Christoph Hellwig ; > Sagi Grimberg > Subject: Re: [PATCH V2 0/2] nvme: Support for fused > NVME_IOCTL_SUBMIT_IO > > On Tue, Feb 09, 2021 at 12:53:17AM +0000, Clay Mayers wrote: > > Is there any other feedback on V2? > > > > My main concern I have about my implementation is how fused requests > > are tunneled through the mq request layer. The 1st request is marked > > as started but it won't be in the device until the 2nd command is > > queued. As Keith pointed out, a device reset can split the two so > > care must be taken to correctly handle this case. Despite this, I > > thought this was a better approach than modifying mq requests to be > > fused. Especially given Christoph's concern of cost vs value. This is the > lightest touch I could come up with. > > > > Further consideration of this patch may need a more compelling use case. > > I've worked on a proprietary storage systems that relied on fused > > NVMeOF support so it seems compelling to me. There's a comment in > > target/core.c that there is "no support for fused commands yet" > > implying it's been considered. Is pci only support for fused too soon > > or too little? What would make it more compelling? > > The complications it introduces to the IO path and error handling for an > archaic feature has me on the "Nak" side. NVMeOF was introduced well after > the spec define Reservations, and the kernel has supported that capability > for many years. I'm not aware of any other use case for fused commands, so > it appears to be dead weight in the spec. Thanks for sharing your perspective. I can see the point that reservations are good enough for many. For VmWare, moving from reservations to cmp/write on SCSI led to an increase in performance (couldn't find an actual # but heard 30% anecdotally). That's a specialized use case (storage for VMs) on a much slower medium that may not translate to more general storage systems or much faster storage. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme