Received: by 2002:a25:6193:0:0:0:0:0 with SMTP id v141csp1013294ybb; Wed, 8 Apr 2020 14:36:38 -0700 (PDT) X-Google-Smtp-Source: APiQypIWUSjTrtRRrV8k7DthDHKjV6XAxc8l+XdZyu3w+1Gbbz0ODFByJNnlm+idHLTggABmMxXw X-Received: by 2002:aca:4e08:: with SMTP id c8mr4137144oib.143.1586381798141; Wed, 08 Apr 2020 14:36:38 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1586381798; cv=none; d=google.com; s=arc-20160816; b=rcNnCRvToMr4iIBt7zWFPybrTgM+YZ7sFmOEkPGJjFLvHkVlBMa6zc1VkXOUcW92CI /pDoySTHiYx8aX1iF6EJ4Sp6LU5D+y2bXeZ0w/qdN1J1Fv/80ukmoCe0Z9qRyFFxWldw yl/w+pXzL7lg5wmdTtLAcYnIj76we+HkrV82NLI3LZqc3FuE0sfJnJ99ANvuCQRzPHqh x2FH2zAvJbCgXlEIcLdNd8c3Y8wc5dhhGoXUy1R0cG/bTWuzm0kgAXJTYqGPpp87ALKL qGXglAjq0u44H9jlH2fCYqC3pTbcUeJO7J4fQAJzmPHJYjo7WYqvwLSu0pzcG/aMj0/n oqUA== 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=FzCCMH0FVXQ03sPS9Blx8PYycG7R5/dfGRSA6QuVW5w=; b=nVO/xy4V7fLy+bf7ySxkqODph3AmGbf4qTLkcRZAsFawJFW2bvoEqKnRfi7343ciR4 9X8JvlB4dCUYhMdCj0at/ndoAsWNQtrQbqniZ/MyUJ5ST7YYZuoWux3bJRSCyRJ7BA3K azOqNwwg3dDIeqgysJSdxUPR0Yda2cYYuT+HYloR2bKhOW/fxqHSldgD4VFlnoSD0I9U 9U+8ikKIoF/Vb2mxV8bOwdp+adc/s8K2e9qrSr0+hjocm+bNFpG/JpoGvKCIRUKs9TPR 11HHZ4IVExr5PFjdPy3wCEYcE5IidWhXISvsbSC37rYTTDy3hEwrMaBqfc93fQpsyKgx 65Eg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=j2P10Vzg; 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 i17si127073oto.218.2020.04.08.14.36.24; Wed, 08 Apr 2020 14:36:38 -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=j2P10Vzg; 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 S1730040AbgDHTi0 (ORCPT + 99 others); Wed, 8 Apr 2020 15:38:26 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:2985 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728725AbgDHTiZ (ORCPT ); Wed, 8 Apr 2020 15:38:25 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 08 Apr 2020 12:36:41 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 08 Apr 2020 12:38:24 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 08 Apr 2020 12:38:24 -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 19:38:24 +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 19:38:23 +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 12:38:21 -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: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) 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=1586374601; bh=FzCCMH0FVXQ03sPS9Blx8PYycG7R5/dfGRSA6QuVW5w=; 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=j2P10VzgKY91EKABc27qxtQBRmIqqfjS1JYnmAPKBKrO/B1S8IJz56Q6xmD/MtHfG VXYbHE/JpFA8Xw2kp9vHG2MGewgoJcZyWCjSm8XGlU+XGpMhYOouL/BGv7ezZPrUFC cGXAuMuS3wuEmHE8eftH0PY49aejq25IOi4CxPrk5Ry6IVOlpduPSCYNYgUDHQ7KQ6 ZA02y6Lodd1Mc+YxkyNuSzIRy58FxS0zFl8GDQYW/Z/4HIOVgZyCOq5UmsTB07ae++ C9KJoEj5LNi6MwcigyxrOZoEwXjD5PwYPz0XHDug/yd27NZNz80m+0XTli9nvmcuQH E5E7NarLS5OXg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/8/20 11:58 AM, Sowjanya Komatineni wrote: > > 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,=20 >>>>>>>> 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=20 >>>>> 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=20 >> inflight happens only during beginning of streaming where buffers=20 >> allocated go 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. correction: With 3 buffers, as soon as buffer is available capture=20 starts. So right most times I see it waiting for few ms before 3rd=20 capture to get through. As only 2 frames single shot can be issued in sequence (inflight=20 requests), instead of waiting for 1 of the request to finish, we can use=20 2 buffers and avoid waiting as 2 buffers are good enough. Will change=20 this in v7.