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[209.132.180.67]) by mx.google.com with ESMTP id q15si2849038ota.87.2020.04.08.20.39.40; Wed, 08 Apr 2020 20:40:07 -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="V/lySZED"; 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 S1726621AbgDIDir (ORCPT + 99 others); Wed, 8 Apr 2020 23:38:47 -0400 Received: from hqnvemgate25.nvidia.com ([216.228.121.64]:14454 "EHLO hqnvemgate25.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726534AbgDIDir (ORCPT ); Wed, 8 Apr 2020 23:38:47 -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 20:37:53 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 08 Apr 2020 20:38:46 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 08 Apr 2020 20:38:46 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 9 Apr 2020 03:38:46 +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; Thu, 9 Apr 2020 03:38:45 +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 20:38:43 -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: 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=1586403473; bh=F3HaYrMPuOWwgOrFNUyJnJrQiX8sKdxipOmM0RTMENg=; 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=V/lySZEDTrNKSUloen7q5QCbi5mqLHaFQ6Y2gcCm/EPx4ZVA0Ml2r/KrvN5qdkA0Y gjw1nZhoHHvu/lQNnDeIcWjV/iouQHEx1u72vmggPBb7jx5fMtqFXkXeachsDRBh6v tIImffl66CeV/sMm6yfOZ1AKgy0i0AVSv/2HOPYrQF8ldIILMwAZzkgBW1y76AAJWq 5x3IiqGODYBo7qF3jjByJMCluRc9sx4gmcTqzYkxuHM97ZCjCJI8fVJsI0nyDYvbEY PB9HNjUIjr3yR0wF7l42smtzt0CZJnSaYEKWGLLYTT8QcdFpDmYTQrr780vxRXbdt/ pOYd4LQkJ/qZw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/8/20 12:38 PM, Sowjanya Komatineni wrote: > > 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=20 >>>>> 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=20 >>>> 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= =20 >>> 2=C2=A0 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=20 >>> shot is issue for 2 frames simultaneous happens only during=20 >>> beginning of start stream and also we set num_buffers to allocate=20 >>> for queue as 3 although 2 is good enough where we will not hit this=20 >>> case even during 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=20 > use 2 buffers and avoid waiting as 2 buffers are good enough. Will=20 > change this in v7. > > > Tested with 3 buffers and by checking outstanding buffers in process by=20 VI hw and holding to start capture till one outstanding buffer in=20 process by HW. Also tested with 2 buffers without checking for outstanding buffers. In both cases, I see same %CPU for the kthreads and is < 1%