linux-kernel - Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b2405c2a-73c0-ad69-ccea-0388caf8045c@gmail.com>
Date:   Wed, 8 Apr 2020 17:21:39 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, frankc@...dia.com,
        hverkuil@...all.nl, sakari.ailus@....fi, helen.koike@...labora.com
Cc:     sboyd@...nel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

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.