From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=psLl=DC=vger.kernel.org=linux-rdma-owner@kernel.org>
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=-5.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,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 9EEEFC4727C
	for <linux-rdma@archiver.kernel.org>; Fri, 25 Sep 2020 11:58:47 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by mail.kernel.org (Postfix) with ESMTP id 2DD9F2083B
	for <linux-rdma@archiver.kernel.org>; Fri, 25 Sep 2020 11:58:47 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="UBU7RbJG"
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1727521AbgIYL6q (ORCPT <rfc822;linux-rdma@archiver.kernel.org>);
        Fri, 25 Sep 2020 07:58:46 -0400
Received: from nat-hk.nvidia.com ([203.18.50.4]:6915 "EHLO nat-hk.nvidia.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1727132AbgIYL6o (ORCPT <rfc822;linux-rdma@vger.kernel.org>);
        Fri, 25 Sep 2020 07:58:44 -0400
Received: from HKMAIL102.nvidia.com (Not Verified[10.18.92.9]) by nat-hk.nvidia.com (using TLS: TLSv1.2, AES256-SHA)
        id <B5f6ddb710000>; Fri, 25 Sep 2020 19:58:41 +0800
Received: from HKMAIL104.nvidia.com (10.18.16.13) by HKMAIL102.nvidia.com
 (10.18.16.11) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 25 Sep
 2020 11:58:37 +0000
Received: from NAM02-SN1-obe.outbound.protection.outlook.com (104.47.36.51) by
 HKMAIL104.nvidia.com (10.18.16.13) with Microsoft SMTP Server (TLS) id
 15.0.1473.3 via Frontend Transport; Fri, 25 Sep 2020 11:58:37 +0000
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none;
 b=jlzDhE2CpEFR5UvMwx36aDOIi8nVK1CJQ+3s+5S/ZeslJRzDEf77mLg7u1W6eMIBP692JvubWExDT4R5A622dAYa6IUW/v34epl+XJC0Jc28LSQ+A8KK0Y/EJ0CWeeKoIsQKvGGO8kNWwHNWc8FESTY1f7VPdHspT0Vb84wnVzkd0pBz82mWoQ0h8BjAYpbhBMpzmNJP1FR4TRG3va55fN2+o9dggqqyiG2EEJNs1HG42+R1aWbkREuTCqqu4g+rIRsQcsME6769pQUyLR+1d/kTiSGY9KI4JHTcBRjQOS9YIxaVsiyEu8ZnCO/2nkLsKnCk4k6/o4tIbdqHgY3rGA==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com;
 s=arcselector9901;
 h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
 bh=i9MYxayAQMlbYSUtc6MXr0ErFpGIN/sIC/TquzhapA0=;
 b=Ss4o6zXfwfTmWOLuTukOd2vjQsAav5B4QFY5AoYQju2RNDSeHW8NPc9Pwrnb9y/0ceYr3nMgyf+95S5TyCORcm8ayy0l4ahmEzb29IzO4zVNi2AMsiu4iTZaOOZV2HCzRHMAAcqhlnhkQ2wLw4Vi/+xr1CtzmG8+uv6GJFAlHt1lvjzCiwmSAxhMnECed3JUx55RTznX+NKmt3y+Oi31Q/+WXxjbzcM9cuB0g/excOXIcyaqjWvQ8kAxZK/3mqjc9yMocBJts5ehQtpTAVFxd1iyTvMeJ/Pux+m0acU5kjaOxtWsyiBvTeBWuNrQi50MaE87wmLE9b+vX39SbFXtBA==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass
 smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com;
 dkim=pass header.d=nvidia.com; arc=none
Authentication-Results: linux.intel.com; dkim=none (message not signed)
 header.d=none;linux.intel.com; dmarc=none action=none header.from=nvidia.com;
Received: from DM6PR12MB3834.namprd12.prod.outlook.com (2603:10b6:5:14a::12)
 by DM5PR12MB2485.namprd12.prod.outlook.com (2603:10b6:4:bb::29) with
 Microsoft SMTP Server (version=TLS1_2,
 cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3412.22; Fri, 25 Sep
 2020 11:58:35 +0000
Received: from DM6PR12MB3834.namprd12.prod.outlook.com
 ([fe80::cdbe:f274:ad65:9a78]) by DM6PR12MB3834.namprd12.prod.outlook.com
 ([fe80::cdbe:f274:ad65:9a78%7]) with mapi id 15.20.3412.024; Fri, 25 Sep 2020
 11:58:35 +0000
Date:   Fri, 25 Sep 2020 08:58:33 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
CC:     Leon Romanovsky <leon@kernel.org>, Christoph Hellwig <hch@lst.de>,
        "Doug Ledford" <dledford@redhat.com>, <linux-rdma@vger.kernel.org>,
        <intel-gfx@lists.freedesktop.org>,
        Roland Scheidegger <sroland@vmware.com>,
        <dri-devel@lists.freedesktop.org>, David Airlie <airlied@linux.ie>,
        "VMware Graphics" <linux-graphics-maintainer@vmware.com>,
        Maor Gottlieb <maorg@nvidia.com>,
        Maor Gottlieb <maorg@mellanox.com>
Subject: Re: [Intel-gfx] [PATCH rdma-next v3 1/2] lib/scatterlist: Add
 support in dynamic allocation of SG table from pages
Message-ID: <20200925115833.GZ9475@nvidia.com>
References: <20200922083958.2150803-1-leon@kernel.org>
 <20200922083958.2150803-2-leon@kernel.org>
 <118a03ef-d160-e202-81cc-16c9c39359fc@linux.intel.com>
 <20200925071330.GA2280698@unreal>
 <adff5752-582c-2065-89e2-924ef732911a@linux.intel.com>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <adff5752-582c-2065-89e2-924ef732911a@linux.intel.com>
X-Originating-IP: [156.34.48.30]
X-ClientProxiedBy: BL1PR13CA0026.namprd13.prod.outlook.com
 (2603:10b6:208:256::31) To DM6PR12MB3834.namprd12.prod.outlook.com
 (2603:10b6:5:14a::12)
MIME-Version: 1.0
X-MS-Exchange-MessageSentRepresentingType: 1
Received: from mlx.ziepe.ca (156.34.48.30) by BL1PR13CA0026.namprd13.prod.outlook.com (2603:10b6:208:256::31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3433.14 via Frontend Transport; Fri, 25 Sep 2020 11:58:35 +0000
Received: from jgg by mlx with local (Exim 4.94)        (envelope-from <jgg@nvidia.com>)        id 1kLmMz-000nQL-L0; Fri, 25 Sep 2020 08:58:33 -0300
X-MS-PublicTrafficType: Email
X-MS-Office365-Filtering-Correlation-Id: fcf473df-5ed4-4e72-f637-08d8614a54cc
X-MS-TrafficTypeDiagnostic: DM5PR12MB2485:
X-MS-Exchange-Transport-Forked: True
X-Microsoft-Antispam-PRVS: <DM5PR12MB2485C89862DB531E934930C8C2360@DM5PR12MB2485.namprd12.prod.outlook.com>
X-MS-Oob-TLC-OOBClassifiers: OLM:7691;
X-MS-Exchange-SenderADCheck: 1
X-Microsoft-Antispam: BCL:0;
X-Microsoft-Antispam-Message-Info: pMV9LxU4FhJo3IJUVpgvPqcdEchPAJA70JaUfKLK4k1NGWSTlTy43Afs28aoX7j3IQjozRAs97nTVNtrwnK5RU38ak7Ts0k7FwbOjxBc3DjE90X0GXeGXDM+/IsC43pV3ET+rGknb/Iv5+VcolaY6lL18M3FaIusR6aH/HqPe1WjdQ2MH8iUPHNiphNXo+6XugRc/nf1TrqdNWZBeZb8Y4TTpeuURugtBQBWL6pjp0Zt6PNuptXX3c8jmC5AY9WpfGzg7bCQz2LNQqaSllTuAKzIzDy8FkH62cPcgoAoww47m1gIzBPwEM1oi0e5N6JQGcg4kEG0BUt/QAR51gR8jguFW5tKD7yykhaUBsGR0u0kEZa98oexnVMGpMVTQJnl
X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM6PR12MB3834.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(376002)(136003)(396003)(346002)(39860400002)(366004)(66946007)(66556008)(186003)(54906003)(2906002)(1076003)(26005)(53546011)(316002)(86362001)(33656002)(5660300002)(36756003)(7416002)(9786002)(9746002)(6916009)(478600001)(2616005)(66476007)(8676002)(4326008)(107886003)(8936002)(426003);DIR:OUT;SFP:1101;
X-MS-Exchange-AntiSpam-MessageData: e1pQNxeP/TLN76OdKBdfxJXBFLssCjTtnS2Sg+COpOc5a/oKkkEmd1WpC9AR2QE/tKIFAvYilsGWgPvMKb+Q1zcagbV1h/O7BgBBH2AUkDWywKirbJ5Ek4y0PCvSeU123qF9hfbUkGyMv4lw/Pp69XIHitctjcnxWH7v5jH87hb/7GRzD1uEQTbsRitWzQxVAJg2MkYhkrmtbwZ3Qk1FV2bOjlpFS5gemOYM9yFj1YGowaUqzXLB8YU7MQB2S18e60oAcVWpEc9ss2+eqvKLePcHlwMjKifkh8CoPsVowtEEetSJestHd5j7Ge0O+uwvbOoD8k8zmCKJw/YVsb+uUtbgcj2EwXfyYgkoOgcwJm+AHD2kTOgZnQB0rxVeKdBrP3QuFN0pJywahgHGIpHEGV4MPXs+9NQs6wxSZrxSTj0er4gs5fDUd1XsnPq/oQ6SkZwJfoQz/cx1/l8X/AEhf8eRBsXebWOjA+P+XEHwAcILC2HjObNXbye3TRrrPOVY9tJmE2MQhltYA7M3kM8ANTx4LAokYt8ZatMqGQKooHaRN700v2ySGU5omELT5iG20ZpzMnlri5IplYPCAAOaEvTfviDs1gDAQtImDpGiupDlarCqaOVp45WKXgpEETnHCYJ1sXhh02MO/ea1bxK/8Q==
X-MS-Exchange-CrossTenant-Network-Message-Id: fcf473df-5ed4-4e72-f637-08d8614a54cc
X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB3834.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Sep 2020 11:58:35.2696
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: e7iCdokvHLeK1A+yiFj3KUn+HddJZG/boTZlaxhSMLJoc/U9cAJtVN/5jaPdOTmV
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR12MB2485
X-OriginatorOrg: Nvidia.com
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
        t=1601035121; bh=i9MYxayAQMlbYSUtc6MXr0ErFpGIN/sIC/TquzhapA0=;
        h=ARC-Seal:ARC-Message-Signature:ARC-Authentication-Results:
         Authentication-Results:Date:From:To:CC:Subject:Message-ID:
         References:Content-Type:Content-Disposition:In-Reply-To:
         X-Originating-IP:X-ClientProxiedBy:MIME-Version:
         X-MS-Exchange-MessageSentRepresentingType:X-MS-PublicTrafficType:
         X-MS-Office365-Filtering-Correlation-Id:X-MS-TrafficTypeDiagnostic:
         X-MS-Exchange-Transport-Forked:X-Microsoft-Antispam-PRVS:
         X-MS-Oob-TLC-OOBClassifiers:X-MS-Exchange-SenderADCheck:
         X-Microsoft-Antispam:X-Microsoft-Antispam-Message-Info:
         X-Forefront-Antispam-Report:X-MS-Exchange-AntiSpam-MessageData:
         X-MS-Exchange-CrossTenant-Network-Message-Id:
         X-MS-Exchange-CrossTenant-AuthSource:
         X-MS-Exchange-CrossTenant-AuthAs:
         X-MS-Exchange-CrossTenant-OriginalArrivalTime:
         X-MS-Exchange-CrossTenant-FromEntityHeader:
         X-MS-Exchange-CrossTenant-Id:X-MS-Exchange-CrossTenant-MailboxType:
         X-MS-Exchange-CrossTenant-UserPrincipalName:
         X-MS-Exchange-Transport-CrossTenantHeadersStamped:X-OriginatorOrg;
        b=UBU7RbJGc72g5nCst20RcXOTriUU+oCCDckomH4l7d67cf1gNfCg0h6Dd9KYzRDUS
         sKgShT2YOL3yJfyXHrIXOqFDqqDKbi9PZAd5zzB3M5DoCpSXxWGYgD7O6NYjkrE5ya
         w8V/kJ4iX0rcRh+OVcJQM6bDrZdFQHr5XB0z5ZrHZl/geDsCLk/uXlQydLeCZjtKW9
         hjDQPYQZP/dH/N8BbbusUwVCVV4ZptczESC4NoSnHMcX850PkScP+IsLMsgBNnq7XT
         1h7EJOUPDC2GbzDuLcCZsjgJIlFOJg5ESgdBMccxUmY5vMm/s2WuuWjBp36ZGA0IYt
         odRFDPnap/PHw==
Precedence: bulk
List-ID: <linux-rdma.vger.kernel.org>
X-Mailing-List: linux-rdma@vger.kernel.org

On Fri, Sep 25, 2020 at 12:41:29PM +0100, Tvrtko Ursulin wrote:
> 
> On 25/09/2020 08:13, Leon Romanovsky wrote:
> > On Thu, Sep 24, 2020 at 09:21:20AM +0100, Tvrtko Ursulin wrote:
> > > 
> > > On 22/09/2020 09:39, Leon Romanovsky wrote:
> > > > From: Maor Gottlieb <maorg@mellanox.com>
> > > > 
> > > > Extend __sg_alloc_table_from_pages to support dynamic allocation of
> > > > SG table from pages. It should be used by drivers that can't supply
> > > > all the pages at one time.
> > > > 
> > > > This function returns the last populated SGE in the table. Users should
> > > > pass it as an argument to the function from the second call and forward.
> > > > As before, nents will be equal to the number of populated SGEs (chunks).
> > > 
> > > So it's appending and growing the "list", did I get that right? Sounds handy
> > > indeed. Some comments/questions below.
> > 
> > Yes, we (RDMA) use this function to chain contiguous pages.
> 
> I will eveluate if i915 could start using it. We have some loops which build
> page by page and coalesce.

Christoph H doesn't like it, but if there are enough cases we should
really have a pin_user_pages_to_sg() rather than open code this all
over the place.

With THP the chance of getting a coalescing SG is much higher, and
everything is more efficient with larger SGEs.

Jason