Received: by 2002:a25:6193:0:0:0:0:0 with SMTP id v141csp963942ybb; Wed, 8 Apr 2020 13:28:37 -0700 (PDT) X-Google-Smtp-Source: APiQypIQqXRW/AcY7tOW52UTQyKaSQchwdzx7dz3oASH5e3PN6GB2rzLXkMP/KVgbl5ZoYbnMxln X-Received: by 2002:aca:bd46:: with SMTP id n67mr3703886oif.120.1586377717526; Wed, 08 Apr 2020 13:28:37 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1586377717; cv=none; d=google.com; s=arc-20160816; b=aS4ojh/2vSEAhDc0Vsw9UwBg7XC8ZEZp6QwK/+xGn2YXJpm59K5M/MrsuxaCpdQVB0 Kglv/8vkrLRcJLzqYmYLk2KX5hsPXoxKg60emjoH+WH6wQyC0o3OtmpA6Ql2OxU83WQR Xul4H5LRqLqkrm+v1wotYd7+/aKk1fG6mSugdYb+gOr9eh8djsZu9uszHF2XVrskUa4a dzOyX7dApeYFYFbXKepuYAulKZpXa7o5CiiaaAXL+hTEPfATlVH0LyqEZgff0mT5xpYs z8Y1fnPK7E497dUsBpfV3246Vuf9aw1BsERDb1fWkTlr71WUH0Afs8PA+POxB4CIu4TK I6zQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:dkim-signature:content-language :content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:references:cc:to:from:subject; bh=WiXwOMB6IdZZe61YJiuIGQp9xJN94uE559/iv1nBzAs=; b=WFges+27XGGNQwnpC9+mAEMjCJC+shshITCXjRrWSnEn/RbT9QpzZS/3kq1dSapGb8 hu5XrcdVvqLtxU4VMe0iVxDADFw0HR6QOa4n2O2ccwcINvpVNLRogKSxJIkVeqEMbQSg MH8alpS4HnMLsdUy+PN/EobV+uT70hPgoqsh8jUNgGkz9ZWmPMnWO+JFpcdATpnyNfEo 94126HgtsBizBsFczAkFkIvPxtfv5rJgNfKAZl3PE3PjoUpKjyOLLVcE5W7ildjMCyLL uVfx4XfgiiznUG6E/+Gb+VKGI5H34zs9dV45CTzYBXMGH6N4U0TpZExbumVsvH2PTIez YA1A== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=fFyW9LaI; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id w16si1573015oog.87.2020.04.08.13.28.24; Wed, 08 Apr 2020 13:28:37 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=fFyW9LaI; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728782AbgDHS64 (ORCPT + 99 others); Wed, 8 Apr 2020 14:58:56 -0400 Received: from hqnvemgate25.nvidia.com ([216.228.121.64]:13573 "EHLO hqnvemgate25.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726730AbgDHS64 (ORCPT ); Wed, 8 Apr 2020 14:58:56 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 08 Apr 2020 11:58:02 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 08 Apr 2020 11:58:55 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 08 Apr 2020 11:58:55 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 8 Apr 2020 18:58:55 +0000 Received: from [10.2.171.241] (10.124.1.5) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 8 Apr 2020 18:58:53 +0000 Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver From: Sowjanya Komatineni To: Dmitry Osipenko , , , , , , CC: , , , , , References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com>

<760d071e-0cbc-b3eb-9231-fb9f9ecb44a6@nvidia.com> <9e317f65-8a02-3b15-cfec-8e0d8374130e@gmail.com> <97b35910-4c93-123a-43a0-eb14476ed0f3@nvidia.com> <84ad4e2d-6ac1-e1f4-1c55-5edaae850631@nvidia.com> <15a879b3-8fb9-6821-3cdc-104ba583ac12@gmail.com> <0c425505-347f-7418-af7e-d121fe0d06dc@nvidia.com> <1a31cd60-739f-0660-1c45-31487d2f2128@nvidia.com> <603084a5-249a-4fe2-3646-e9335ef9ab43@nvidia.com> <7895b9c6-f27d-8939-73d7-67d785e1a8b7@nvidia.com>

<15d8b525-67b5-b437-f7fd-89f80cd0d9f6@nvidia.com> Message-ID: Date: Wed, 8 Apr 2020 11:58:52 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <15d8b525-67b5-b437-f7fd-89f80cd0d9f6@nvidia.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To DRHQMAIL107.nvidia.com (10.27.9.16) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1586372282; bh=WiXwOMB6IdZZe61YJiuIGQp9xJN94uE559/iv1nBzAs=; h=X-PGP-Universal:Subject:From:To:CC:References:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Transfer-Encoding: Content-Language; b=fFyW9LaIcFrNndkItDjS2qGndrz4UgUFDjPq4tudYfhTi00UY4WZy0FIKk49HhNOE NiJdPomwPyEIz+VIalXMiDC6qJU6BPFqDxGZkq6UXKcKW/u60DaHkWo/v0iWh7x/a+ 5QqsZHrpmgPppeExol8f4P9/lJZhWP+kVoCGIjmk1UrjVbG8I11ox652XWtQPtzHHl ++wD38kDFinJCbzgj7lt3tLLMnk1oizZVxNhvsHi27rFlAszVe82VkBAjKFBvTtvQe mMCA4jKF/OsWzOWNHE7Ef3fmHjDZbau4v+XZUdGoNrVAFrwqPdkXsQxlgdqZtOjLAK 6F9w/AXFhy1CQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/8/20 10:45 AM, Sowjanya Komatineni wrote: > > On 4/8/20 7:21 AM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 08.04.2020 03:00, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> ... >>>>>>> I suppose that taking a shot takes at least few milliseconds, which >>>>>>> should be unacceptable to waste. >>>>>> As long as buffers are in queue we have to keep processing each >>>>>> buffer and between buffers obviously we have to wait for previous >>>>>> frames to finish and this why we have separate thread for frame >>>>>> finish where we can have next buffer capture ready and issue while >>>>>> previous frame memory write happens >>>> Also we specified numbers buffers as 3 to vb2 queue. So this is rare >>>> case but to prevent issuing more than 2 at a time as VI HW is only >>>> double buffered and syncpt fifo max depth is 2 added this to be safer. >>> To be more clear, when more buffers are enqueued from userspace always >>> capture list will be full and thread will be busy in capture till=20 >>> either >>> error or stop stream request happens. >>> >> If kthreads take more than 1% of CPU time during capture (video) with >> more than 2 buffers in queue, then it's not good and I think you should >> do something about it. If kthreads stay at ~0%, then it should be okay >> as-is. > > VI outstanding requests max can only be 2=C2=A0 as syncpt fifo depth is 2= =C2=A0=20 > and waiting to issue next capture when already 2 captures are inflight=20 > happens only during beginning of streaming where buffers allocated go=20 > thru capture for first time after queuing. > > same buffers are returned to userspace after capture and same=20 > allocated buffers will be queued back for subsequent captures. > > So this case of holding to issue single shot when already single shot=20 > is issue for 2 frames simultaneous happens only during beginning of=20 > start stream and also we set num_buffers to allocate for queue as 3=20 > although 2 is good enough where we will not hit this case even during=20 > streaming start with 2 buffers > As 2 buffers are good enough to be clear will update in v7 to use 2=20 buffers so we don't need to check for more than 2 outstanding buffers.