From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailout2.samsung.com (mailout2.samsung.com [203.254.224.25]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2DB413644D2 for ; Wed, 4 Feb 2026 06:07:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=203.254.224.25 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770185250; cv=none; b=c4ZMRVulBZoV3bdGcCXn7F+mogqatKvimHxzagOIbNCrNB4JZsApLVnZXjuem1+ylot8EGkvRVBxJGH910pcJtamvb64IJpSLMvP4md54Om0/8QN6Txvl5z++dnlVeRy00Q5h1q/yUpvGk1RavxI0Hyc8mgCjYK2nyIvajgpRv4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770185250; c=relaxed/simple; bh=vFeASoXmH/a8+nINHgGsmh6ICV7WwiJIChiSbgDwE7s=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:From:In-Reply-To: Content-Type:References; b=CoLRBc0XpPFs2o+m7XHF9f9J4+irlPF3u+B9CkBjBtbHnOnEUycNm00VdghFuVb5K3nkOA0YtjzBP4Qvh47c6zC4zq5sHfFoAjFYlnJ1EDYWr673bYAPNpb0w9PVzAH99lby8TDe1Q9FUfCqEIRSrMsJ0W9bM6B7mInDqfpMQNw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com; spf=pass smtp.mailfrom=samsung.com; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b=NhzBjLSH; arc=none smtp.client-ip=203.254.224.25 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=samsung.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b="NhzBjLSH" Received: from epcas5p2.samsung.com (unknown [182.195.41.40]) by mailout2.samsung.com (KnoxPortal) with ESMTP id 20260204060727epoutp028496a3769ff5cb680799c05c06836c06~Q9hqm4Bu60207102071epoutp02C for ; Wed, 4 Feb 2026 06:07:27 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout2.samsung.com 20260204060727epoutp028496a3769ff5cb680799c05c06836c06~Q9hqm4Bu60207102071epoutp02C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1770185247; bh=y2frTBlrPcApGJAKcojyrODxcLgxJHU1QEnp9KWJoZE=; h=Date:Subject:To:Cc:From:In-Reply-To:References:From; b=NhzBjLSHtZQSQfwpotD0ry+Zimlaaw5fqm639OJbdbhO5fR5z5AnqlhFlOCe902o8 frZCx7w8qfrbc9ahl5e4C1eLYZNUptEigCQ8ZEOyCMxJPQOOiJ1ezeBjZ7cSv9MUPd pWrdY+SkrHWCbDZFh9P9kvzipTxVl2Dyw8JReVZ8= Received: from epsnrtp02.localdomain (unknown [182.195.42.154]) by epcas5p2.samsung.com (KnoxPortal) with ESMTPS id 20260204060727epcas5p232ff332ff546f37733e37b0c13d6cada~Q9hqaEc0W0625406254epcas5p2u; Wed, 4 Feb 2026 06:07:27 +0000 (GMT) Received: from epcas5p4.samsung.com (unknown [182.195.38.94]) by epsnrtp02.localdomain (Postfix) with ESMTP id 4f5VHy44lQz2SSKd; Wed, 4 Feb 2026 06:07:26 +0000 (GMT) Received: from epsmtip2.samsung.com (unknown [182.195.34.31]) by epcas5p3.samsung.com (KnoxPortal) with ESMTPA id 20260204060726epcas5p3816adfde071ae343471ac7a6a33a0e82~Q9ho7YiaV1775217752epcas5p3N; Wed, 4 Feb 2026 06:07:26 +0000 (GMT) Received: from [107.122.10.194] (unknown [107.122.10.194]) by epsmtip2.samsung.com (KnoxPortal) with ESMTPA id 20260204060722epsmtip24e8143a262629db8288b2256b0e51ace~Q9hlWsA3n1083210832epsmtip2D; Wed, 4 Feb 2026 06:07:22 +0000 (GMT) Message-ID: Date: Wed, 4 Feb 2026 11:37:20 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [LSF/MM/BPF TOPIC] dmabuf backed read/write To: Keith Busch , Pavel Begunkov Cc: linux-block@vger.kernel.org, io-uring , "linux-nvme@lists.infradead.org" , =?UTF-8?Q?Christian_K=C3=B6nig?= , Christoph Hellwig , Kanchan Joshi , Nitesh Shetty , "lsf-pc@lists.linux-foundation.org" Content-Language: en-US From: Anuj Gupta/Anuj Gupta In-Reply-To: Content-Transfer-Encoding: 8bit X-CMS-MailID: 20260204060726epcas5p3816adfde071ae343471ac7a6a33a0e82 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" CMS-TYPE: 105P cpgsPolicy: CPGSC10-542,Y X-CFilter-Loop: Reflected X-CMS-RootMailID: 20260203180716epcas5p1c9658e583e26197b515f6db07a100aa9 References: <4796d2f7-5300-4884-bd2e-3fcc7fdd7cea@gmail.com> On 2/3/2026 11:37 PM, Keith Busch wrote: > Thanks for submitting the topic. The performance wins look great, but > I'm a little surpised passthrough didn't show any difference. We're > still skipping a bit of transformations with the dmabuf compared to not > having it, so maybe it's just a matter of crafting the right benchmark > to show the benefit. > Those numbers were from a drive that saturates at ~5M IOPS, sopassthrough didn’t have much headroom. I did a quick run with two such drives and saw a small improvement (~2–3%): ~5.97 MIOPS -> ~6.13 MIOPS, but I’ll try tweaking the kernel config a bit to see if there’s more headroom. +1 on the topic - I'm interested in attending the discussion and reviewing/testing v3 when it lands. Thanks, Anuj