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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7ABF5C05027 for ; Mon, 6 Feb 2023 16:11:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231487AbjBFQLC (ORCPT ); Mon, 6 Feb 2023 11:11:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47870 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231718AbjBFQKz (ORCPT ); Mon, 6 Feb 2023 11:10:55 -0500 Received: from mailout2.w1.samsung.com (mailout2.w1.samsung.com [210.118.77.12]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8196252BB for ; Mon, 6 Feb 2023 08:10:33 -0800 (PST) Received: from eucas1p1.samsung.com (unknown [182.198.249.206]) by mailout2.w1.samsung.com (KnoxPortal) with ESMTP id 20230206161029euoutp0299a40c15c26deb66505b4bb4ae9118a4~BSB3ewj5k2289522895euoutp02m for ; Mon, 6 Feb 2023 16:10:29 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout2.w1.samsung.com 20230206161029euoutp0299a40c15c26deb66505b4bb4ae9118a4~BSB3ewj5k2289522895euoutp02m DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1675699829; bh=KwqIfnaMCdcPNNA877/cf4Jb1KTTKgjFLq02LqKcLLs=; h=Date:Subject:To:CC:From:In-Reply-To:References:From; b=loKuK9g09c1RVKd+cUfTh8QOKGOzPKziugSN5E6ZkZh8eVPTelm7RqkGt8h5lZyyU Rr1PJs5Ohl/aTk/uwZrJ9d6kCENUuDK+lsZ73W/Z1CD2O2ChArmFUj3ZijChbbiH/n VcujQju+bAez80biH6+3wiTiJsWS8e6dcgKsbGMo= Received: from eusmges2new.samsung.com (unknown [203.254.199.244]) by eucas1p1.samsung.com (KnoxPortal) with ESMTP id 20230206161028eucas1p183b87b561bb7b75e3ca4b5683f79b1de~BSB2X_sho0830308303eucas1p12; Mon, 6 Feb 2023 16:10:28 +0000 (GMT) Received: from eucas1p1.samsung.com ( [182.198.249.206]) by eusmges2new.samsung.com (EUCPMTA) with SMTP id 81.FE.13597.47621E36; Mon, 6 Feb 2023 16:10:28 +0000 (GMT) Received: from eusmtrp2.samsung.com (unknown [182.198.249.139]) by eucas1p2.samsung.com (KnoxPortal) with ESMTPA id 20230206161027eucas1p2fb014bbe7b69f3bf4ec1ff4b9edc64ba~BSB2EAUIb0105301053eucas1p20; Mon, 6 Feb 2023 16:10:27 +0000 (GMT) Received: from eusmgms1.samsung.com (unknown [182.198.249.179]) by eusmtrp2.samsung.com (KnoxPortal) with ESMTP id 20230206161027eusmtrp28b1854f87e136fe15fb2a0ac52a21237~BSB2BO0rV0805208052eusmtrp2H; Mon, 6 Feb 2023 16:10:27 +0000 (GMT) X-AuditID: cbfec7f4-207ff7000000351d-7d-63e126741118 Received: from eusmtip2.samsung.com ( [203.254.199.222]) by eusmgms1.samsung.com (EUCPMTA) with SMTP id 15.9E.02722.37621E36; Mon, 6 Feb 2023 16:10:27 +0000 (GMT) Received: from CAMSVWEXC02.scsc.local (unknown [106.1.227.72]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20230206161027eusmtip2524d03efdec77f9169817980fbfa4ec4~BSB14n0PX2791827918eusmtip20; Mon, 6 Feb 2023 16:10:27 +0000 (GMT) Received: from [192.168.1.19] (106.210.248.242) by CAMSVWEXC02.scsc.local (2002:6a01:e348::6a01:e348) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 6 Feb 2023 16:10:25 +0000 Message-ID: <62f6beda-a946-638b-950a-444a5705dcce@samsung.com> Date: Mon, 6 Feb 2023 21:40:23 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH] brd: improve performance with blk-mq Content-Language: en-US To: Christoph Hellwig CC: , , , From: Pankaj Raghav In-Reply-To: <20230206155048.GA13392@lst.de> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [106.210.248.242] X-ClientProxiedBy: CAMSVWEXC01.scsc.local (2002:6a01:e347::6a01:e347) To CAMSVWEXC02.scsc.local (2002:6a01:e348::6a01:e348) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFmpjleLIzCtJLcpLzFFi42LZduznOd0StYfJBp+O81usvtvPZrFy9VEm i723tC1uTHjK6MDicflsqcemVZ1sHrtvNrB5fN4kF8ASxWWTkpqTWZZapG+XwJXx6fIdpoIP HBXvZn1mbGDsYO9i5OSQEDCRmLfwMQuILSSwglHixeLCLkYuIPsLo8SDs8tYIJzPjBJTdp1m gum49PYEG0THckaJRzs84Io+b+tnhHB2MkrMadzPCFLFK2AncfvAOWYQm0VAReLssbcsEHFB iZMzn4DZogJREk0XfoLZwgKWEouOHgWrZxYQl7j1ZD7YZhEBJYmnr84yQsSTJZ6/vwF0BQcH m4CWRGMn2DucAjoSu1q/skCUaEq0bv/NDmHLS2x/O4cZ4gFliS+f3kDZtRKnttxiArlZQuAO h8TGp0uZQWZKCLhI3HutDlEjLPHq+BZocMlI/N85HxoQ1RJPb/xmhuhtYZTo37meDaLXWqLv TA6E6SjRsU0bwuSTuPFWEOIaPolJ26YzT2BUnYUUDrOQ/DsLyQOzkDywgJFlFaN4amlxbnpq sVFearlecWJucWleul5yfu4mRmBSOf3v+JcdjMtffdQ7xMjEwXiIUYKDWUmE1/TAg2Qh3pTE yqrUovz4otKc1OJDjNIcLErivNq2J5OFBNITS1KzU1MLUotgskwcnFINTHHnWlvV/U7lT1jN diyn4Idd6gr96pcNr49X7Jf8Pv1SteGb2mrx+9tcz01eb1DF5RCRH9h8OviqdIq1iezU2Re6 sqq2P6vu9z94J1O+KFTX6eL9quU9b24uZl9k8/JWS2N/4jGrXfGz5Rb+XD7F/Br7Z+9lYirF cS4HtX6bsz/9/PP1EXbWlvMFij9aHhUGn79hxsGwXXs68/5rKpJZfWqH+I6eu3Q8P3xh8T7n 0iOZD196TT6/R/uZ+b2DHi8/TpZc29Iq+3Opps+P/EcXmHuMyjRWLOxItuh7aLxGTqrr6odj HmuXcZkrNtxVFmwX0dPME4o53nV7jvCRzOmZiTGzZk1zj1CPPduttWzWLSWW4oxEQy3mouJE ANYpBK6ZAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrHIsWRmVeSWpSXmKPExsVy+t/xe7rFag+TDe5fNbVYfbefzWLl6qNM FntvaVvcmPCU0YHF4/LZUo9NqzrZPHbfbGDz+LxJLoAlSs+mKL+0JFUhI7+4xFYp2tDCSM/Q 0kLPyMRSz9DYPNbKyFRJ384mJTUnsyy1SN8uQS/j0+U7TAUfOCrezfrM2MDYwd7FyMkhIWAi centCbYuRi4OIYGljBKfb15ihkjISHy68hGqSFjiz7UuNhBbSOAjo8S3+1kQDTsZJaYuvMwI kuAVsJO4feAcWDOLgIrE2WNvWSDighInZz4Bs0UFoiRunn/IBGILC1hKLDp6FKyeWUBc4taT +WBxEQEliaevzjJCxJMlnr+/AXXdXUaJq78XABVxcLAJaEk0doIdxymgI7Gr9SsLRL2mROv2 3+wQtrzE9rdzoJ5Rlvjy6Q2UXSvx+e8zxgmMorOQnDcLyRmzkIyahWTUAkaWVYwiqaXFuem5 xYZ6xYm5xaV56XrJ+bmbGIERue3Yz807GOe9+qh3iJGJg/EQowQHs5IIr+mBB8lCvCmJlVWp RfnxRaU5qcWHGE2BYTSRWUo0OR+YEvJK4g3NDEwNTcwsDUwtzYyVxHk9CzoShQTSE0tSs1NT C1KLYPqYODilGpicVwVtu7nWbmKFmbv2ypM33umGM7uXrOGPC1g35cNWm8tFs1KYjPObOGUa WQ5Hbf7dd4L7rfGyX2z/DrF1v5zyw/6Sz9TnqmpNNeUF5f+f+n9+xjs5Zffi+YUdt5IObe0U n+V+52D//vW+F3cabP8SZbh9Y+l9D97jFTaCmg0nFvsc6btV+33djnb/lpdz+wr1BRZ2ylWU Zro/fzrzWbezHmuvbu7ENU2sEeZKjFOiIzts9tmc+x3fJ5m1uHHSa9XlemzGs213OHc/Stmc bnYtLtvi99dN8RK6exMeOnqnu8qExtYX8Kke27jPrfDTwyDO72o7Ls9/Y76D5U7An32fG3ur jtxrurP/+aWlcuVKLMUZiYZazEXFiQBb9laqUQMAAA== X-CMS-MailID: 20230206161027eucas1p2fb014bbe7b69f3bf4ec1ff4b9edc64ba X-Msg-Generator: CA X-RootMTR: 20230203103127eucas1p293a9fa97366fc89c62f18053be6aca1f X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20230203103127eucas1p293a9fa97366fc89c62f18053be6aca1f References: <20230203103005.31290-1-p.raghav@samsung.com> <20230203103005.31290-2-p.raghav@samsung.com> <20230206155048.GA13392@lst.de> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2023-02-06 21:20, Christoph Hellwig wrote: > On Fri, Feb 03, 2023 at 04:00:06PM +0530, Pankaj Raghav wrote: >> move to blk-mq based request processing as brd is one of the few drivers >> that still uses submit_bio interface. The changes are pretty trivial >> to start using blk-mq. The performance increases up to 125% for direct IO >> read workloads. There is a slight dip in performance for direct IO write >> workload but considering the general performance gain with blk-mq >> support, it is not a lot. > > Can you find out why writes regress, and what improves for reads? > Definitely. I tried to do similar experiments in null blk with submit_bio & blk-mq backend and noticed a similar pattern in performance. I will look into it next week as I am OOO rest of the week. > In general blk-mq is doing a lot more work for better batching, but much > of that batching should not matter for a simple ramdisk. So the results > look a little odd to me, and extra numbers and explanations would > really help. Let me know if you think I am missing something in the code that can cause this behavior! Thanks.