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Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver
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From:   Dmitry Osipenko <digetx@gmail.com>
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Date:   Wed, 8 Apr 2020 17:21:39 +0300
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08.04.2020 03:00, Sowjanya Komatineni пишет:
...
>>>>> 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 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.