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 8272DC83000 for ; Mon, 30 Jun 2025 06:02:28 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=8lQyPGKhSq9KW7FgWNucgL1V7RFNBeyUyiQqzpmoX9o=; b=DOZ52I92vlYQR1vqo70wUcz1XW SZM2mJjBRMfCXUC3v4MsJKc8R78hpPa0kvvCElA0qQLcJ6OqUA1Ob07jReG/psWeIB4JL7pKcbCbr nPQbE35Y6/bNTPzi1WQh/kQRm3lmQQzkhAVUoQvgV5zd4MKuii2ZSZijXK5eBksVoOMPWxGIVSbSD cxnDJq6Tm596JDYow1p+aA/92hfQG8oD3XryXcj6Cg9zuPq64A5rqsaHEbCFhMJR04hGsZUt5xfPD fMDxGLoampI0lVGnd1h5CidWKfajiKuPLyZWdr7fZi3EbkCheezcEt7G4nilF1uUzjyzCylfVz7pJ v7wuAtzg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uW7ay-00000001InN-2n0u; Mon, 30 Jun 2025 06:02:24 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uW7ZC-00000001Ic6-0i9b for linux-nvme@lists.infradead.org; Mon, 30 Jun 2025 06:00:35 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id A5C3368D05; Mon, 30 Jun 2025 08:00:17 +0200 (CEST) Date: Mon, 30 Jun 2025 08:00:16 +0200 From: Christoph Hellwig To: Keith Busch Cc: Christoph Hellwig , Keith Busch , linux-nvme@lists.infradead.org Subject: Re: [PATCH] nvme: uring_cmd specific request_queue for SGLs Message-ID: <20250630060016.GA28775@lst.de> References: <20250624211444.2835077-1-kbusch@meta.com> <20250625060915.GB9391@lst.de> <20250626051413.GC23248@lst.de> <20250627072524.GA1329@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250629_230034_346306_EFD9249A X-CRM114-Status: GOOD ( 13.81 ) 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 Fri, Jun 27, 2025 at 09:34:56AM -0600, Keith Busch wrote: > Back to this patch, I get that this uring_cmd path wouldn't be able to > use the more efficient coalesced mapping when the IOMMU is on, and > instead map each segment indiviually. I think that's still better than > the alternative, though. My back on the envelope calculations (for 8 byte metadata chunks) suggests otherwise, but I never got around fully benchmarking it. If you do have a representation workload that you care about I'd love to see the numbers.