[ros-users] Fwd: publishing large images at high fps using image_transport

[Brian Gerkey]

hi Dejan,

It would be interesting to see some data from a profiler to understand
where the publishing node is spending its time.  We usually use
sysprof: http://pr.willowgarage.com/wiki/sysprof .

	brian.

On Sun, Apr 18, 2010 at 1:37 PM, Dejan Pangercic
<dejan.pangercic at gmail.com> wrote:
> Hi there,
>
> I ran the program with the valgrind and found nothing fishy. Moreover
> it turned out that the decay in publishing rate only happens when
> there is a subscriber such as e.g. image_view subscribed to the topic.
> What I then tried next was to subscribe to the output topic with 3
> "rostopic hz /image_topic_2" commands only - see also an attached
> rxgraph plot.
> This resulted in every subscription having less and less publishing
> rate (~ 30, 25 and 26 Hz respectively). Once again I ran this on one
> machine and over the loopback. The program publishing images is now
> also in tum-ros-pkg repo:
> http://tum-ros-pkg.svn.sourceforge.net/viewvc/tum-ros-pkg/perception/image_algos/utils/openCV_to_ros.cpp?revision=432&view=markup
> if someone wants to give it a try.
>
> Could the decay in publishing rate be attributed to the way ROS's
> subscribe mechanism handles the copying of data?
>
> cheers, D.
>
>
> On Fri, Apr 16, 2010 at 9:47 PM, Josh Faust <jfaust at willowgarage.com> wrote:
>> Whoops, should've looked at the attached source.  In general a profiler is
>> going to tell you what's taking time far better than we will.
>>
>> Josh
>>
>> On Fri, Apr 16, 2010 at 12:33 PM, Dejan Pangercic
>> <dejan.pangercic at gmail.com> wrote:
>>>
>>> Hi Josh,
>>>
>>> I did not do profiling yet. However, since I read the image only once
>>> when I start the program and then publish it from the memory, it can
>>> not be harddrive.
>>> D.
>>>
>>> On Fri, Apr 16, 2010 at 9:00 PM, Josh Faust <jfaust at willowgarage.com>
>>> wrote:
>>> > Have you tried profiling it to see where the time is being spent, and
>>> > where
>>> > the bottleneck is?  1.8MB * 30 = 54MB/sec, which could actually be
>>> > harddrive-limited depending on the drive you're reading from.
>>> >
>>> > Josh
>>> >
>>> > On Fri, Apr 16, 2010 at 11:26 AM, Dejan Pangercic
>>> > <dejan.pangercic at gmail.com> wrote:
>>> >>
>>> >> Hi there,
>>> >>
>>> >> I using an attached program to read an image from a disk and to then
>>> >> continously publish it on an image topic at 30 fps. On _one_ machine
>>> >> over loopback. When I tried it with a 1608x1236+0+0 color image
>>> >> (1.8MB) and then used rostopic hz to display the publishing rate of
>>> >> topic,
>>> >> the most that I got was around 12, 13 Hz.
>>> >> Any idea what would cause such a low performance? At what rates and
>>> >> sizes do you folks usually send images around?
>>> >>
>>> >> thx and cheers, D.
>>> >>
>>> >> --
>>> >> MSc. Dejan Pangercic
>>> >> PhD Student/Researcher
>>> >> Computer Science IX
>>> >> Technische Universität München
>>> >> Telephone: +49 (89) 289-17780
>>> >> E-Mail: dejan.pangercic at in.tum.de
>>> >> WWW: http://ias.cs.tum.edu/people/pangercic
>>> >>
>>> >> _______________________________________________
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>>> >>
>>> >
>>> >
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>>> >
>>>
>>>
>>>
>>> --
>>> MSc. Dejan Pangercic
>>> PhD Student/Researcher
>>> Computer Science IX
>>> Technische Universität München
>>> Telephone: +49 (89) 289-17780
>>> E-Mail: dejan.pangercic at in.tum.de
>>> WWW: http://ias.cs.tum.edu/people/pangercic
>>> _______________________________________________
>>> ros-users mailing list
>>> ros-users at code.ros.org
>>> https://code.ros.org/mailman/listinfo/ros-users
>>
>>
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>
>
>
> --
> MSc. Dejan Pangercic
> PhD Student/Researcher
> Computer Science IX
> Technische Universität München
> Telephone: +49 (89) 289-17780
> E-Mail: dejan.pangercic at in.tum.de
> WWW: http://ias.cs.tum.edu/people/pangercic
>
>
>
> --
> MSc. Dejan Pangercic
> PhD Student/Researcher
> Computer Science IX
> Technische Universität München
> Telephone: +49 (89) 289-17780
> E-Mail: dejan.pangercic at in.tum.de
> WWW: http://ias.cs.tum.edu/people/pangercic
>
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>