real time question : RR vs FF?

[Stefan Kost]

Am 30.04.2011 11:24, schrieb Victor henri:
> I answer to myself
> 
> It was quite easy to find...
> In the 'testrtpool.c' file, in the 'default-push' function, I just had to
> replace "SCHED_RR" by "SCHED_FIFO"
> On the other hand, 'param.sched_priority' is set to to 50, which can be changed
> also according to the priority one wants to give to the process;

I hope you have a good reason for using SCHED_FIFO. 1st I hope you understand
that you will only get scheduling priority, I you are not running fast enough,
this is *not* the solution. 2nd I hope you understand the dangers of SCHED_FIFO
vs. SCHED_RR.

Stefan

> 
> Victor
> 
> --------------------------------------------------------------------------------
> From: nadaeck at hotmail.com
> To: gstreamer-devel at lists.freedesktop.org
> Subject: real time question : RR vs FF?
> Date: Thu, 28 Apr 2011 04:34:39 +0200
> 
> Hello
> 
> I have made an app that displays the harmonics in 3d.
> 
> I want to be able to run it in real-time; I have used the 'rtpool-test' code
> from the gstreamer core examples (streams->rtpool-test.c) and it works. However,
> I have seen that this grants me a priority of 90 with a 'RR' policy. Is it
> possible to change the code code to get 'FIFO' policy? If yes, please how could
> I do this? I have tied to use the set_schedparam code, but I got the 'Invalid
> argument' during 'pthread_attr_setschedparam (&attr, &sched)' error... (as well
> as starting the app with 'chrt -r -p my-pid')
> 
> Another question : this code grants real time for Gstreamer code, but what about
> other code code (not Gstreamer) that follows it? The app is written like this :
> GTK GUI with a 'Play" button, that starts playing the sound with Gstreamer, and
> the 'spectrum' element send messages to the bus; everytime the "message handler"
> function retrives the values of the spectrum, there is a call to a function that
> display the values of the spectrum in a SDL/OpenGL window. My question is : is
> the display in the SDL/OpenGL window done also with the RR policy or back with
> TS policy?
> 
> When I run the app (its name is 'spectrum3d', then when I run 'ps -cLe' in a
> terminal to see all the threads of the app, I see this :
> 
>  5265  5265 TS   19 pts/0    00:00:01 spectrum3d
>  5265  5267 TS   19 pts/0    00:00:00 threaded-ml
>  5265  5268 TS   19 pts/0    00:00:00 threaded-ml
>  5265  5270 TS   19 pts/0    00:00:00 task0
>  5265  5271 TS   19 pts/0    00:00:00 spectrum3d
>  5265  5272 RR   90 pts/0    00:00:01 alsasrc:src
> 
> The 1st pid is the Gtk GUI; the last one must be the gstreamer sound reading,
> since its policy is RR; but I don't know what the other pid represent...
> 
> thanks for your help
> 
> Victor
> 
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> 
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